* [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
@ 2019-10-30 23:31 tranmanphong
2019-10-30 23:31 ` Phong Tran
` (2 more replies)
0 siblings, 3 replies; 23+ messages in thread
From: tranmanphong @ 2019-10-30 23:31 UTC (permalink / raw)
Sync the format with current state of kernel documentation.
This change base on rcu-dev branch
what changed:
- Format bullet lists
- Add literal blocks
Signed-off-by: Phong Tran <tranmanphong at gmail.com>
---
Documentation/RCU/index.rst | 1 +
.../RCU/{whatisRCU.txt => whatisRCU.rst} | 150 +++++++++++-------
2 files changed, 90 insertions(+), 61 deletions(-)
rename Documentation/RCU/{whatisRCU.txt => whatisRCU.rst} (91%)
diff --git a/Documentation/RCU/index.rst b/Documentation/RCU/index.rst
index 627128c230dc..b9b11481c727 100644
--- a/Documentation/RCU/index.rst
+++ b/Documentation/RCU/index.rst
@@ -8,6 +8,7 @@ RCU concepts
:maxdepth: 3
arrayRCU
+ whatisRCU
rcu
listRCU
NMI-RCU
diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.rst
similarity index 91%
rename from Documentation/RCU/whatisRCU.txt
rename to Documentation/RCU/whatisRCU.rst
index 58ba05c4d97f..70d0e4c21917 100644
--- a/Documentation/RCU/whatisRCU.txt
+++ b/Documentation/RCU/whatisRCU.rst
@@ -1,15 +1,18 @@
+.. _rcu_doc:
+
What is RCU? -- "Read, Copy, Update"
+======================================
Please note that the "What is RCU?" LWN series is an excellent place
to start learning about RCU:
-1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
-2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
-3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
-4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
- 2010 Big API Table http://lwn.net/Articles/419086/
-5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
- 2014 Big API Table http://lwn.net/Articles/609973/
+| 1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
+| 2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
+| 3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
+| 4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
+| 2010 Big API Table http://lwn.net/Articles/419086/
+| 5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
+| 2014 Big API Table http://lwn.net/Articles/609973/
What is RCU?
@@ -51,6 +54,7 @@ never need this document anyway. ;-)
1. RCU OVERVIEW
+----------------
The basic idea behind RCU is to split updates into "removal" and
"reclamation" phases. The removal phase removes references to data items
@@ -118,6 +122,7 @@ Read on to learn about how RCU's API makes this easy.
2. WHAT IS RCU'S CORE API?
+---------------------------
The core RCU API is quite small:
@@ -166,7 +171,7 @@ synchronize_rcu()
read-side critical sections on all CPUs have completed.
Note that synchronize_rcu() will -not- necessarily wait for
any subsequent RCU read-side critical sections to complete.
- For example, consider the following sequence of events:
+ For example, consider the following sequence of events::
CPU 0 CPU 1 CPU 2
----------------- ------------------------- ---------------
@@ -248,13 +253,13 @@ rcu_dereference()
Common coding practice uses rcu_dereference() to copy an
RCU-protected pointer to a local variable, then dereferences
- this local variable, for example as follows:
+ this local variable, for example as follows::
p = rcu_dereference(head.next);
return p->data;
However, in this case, one could just as easily combine these
- into one statement:
+ into one statement::
return rcu_dereference(head.next)->data;
@@ -267,7 +272,7 @@ rcu_dereference()
Note that the value returned by rcu_dereference() is valid
only within the enclosing RCU read-side critical section [1].
- For example, the following is -not- legal:
+ For example, the following is -not- legal::
rcu_read_lock();
p = rcu_dereference(head.next);
@@ -315,6 +320,7 @@ rcu_dereference()
The following diagram shows how each API communicates among the
reader, updater, and reclaimer.
+::
rcu_assign_pointer()
@@ -377,10 +383,12 @@ for specialized uses, but are relatively uncommon.
3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
+-----------------------------------------------
This section shows a simple use of the core RCU API to protect a
global pointer to a dynamically allocated structure. More-typical
uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt.
+::
struct foo {
int a;
@@ -467,13 +475,14 @@ arrayRCU.txt, and NMI-RCU.txt.
4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
+--------------------------------------------
In the example above, foo_update_a() blocks until a grace period elapses.
This is quite simple, but in some cases one cannot afford to wait so
long -- there might be other high-priority work to be done.
In such cases, one uses call_rcu() rather than synchronize_rcu().
-The call_rcu() API is as follows:
+The call_rcu() API is as follows::
void call_rcu(struct rcu_head * head,
void (*func)(struct rcu_head *head));
@@ -481,7 +490,7 @@ The call_rcu() API is as follows:
This function invokes func(head) after a grace period has elapsed.
This invocation might happen from either softirq or process context,
so the function is not permitted to block. The foo struct needs to
-have an rcu_head structure added, perhaps as follows:
+have an rcu_head structure added, perhaps as follows::
struct foo {
int a;
@@ -490,7 +499,7 @@ have an rcu_head structure added, perhaps as follows:
struct rcu_head rcu;
};
-The foo_update_a() function might then be written as follows:
+The foo_update_a() function might then be written as follows::
/*
* Create a new struct foo that is the same as the one currently
@@ -520,7 +529,7 @@ The foo_update_a() function might then be written as follows:
call_rcu(&old_fp->rcu, foo_reclaim);
}
-The foo_reclaim() function might appear as follows:
+The foo_reclaim() function might appear as follows::
void foo_reclaim(struct rcu_head *rp)
{
@@ -552,7 +561,7 @@ o Use call_rcu() -after- removing a data element from an
If the callback for call_rcu() is not doing anything more than calling
kfree() on the structure, you can use kfree_rcu() instead of call_rcu()
-to avoid having to write your own callback:
+to avoid having to write your own callback::
kfree_rcu(old_fp, rcu);
@@ -560,6 +569,7 @@ Again, see checklist.txt for additional rules governing the use of RCU.
5. WHAT ARE SOME SIMPLE IMPLEMENTATIONS OF RCU?
+------------------------------------------------
One of the nice things about RCU is that it has extremely simple "toy"
implementations that are a good first step towards understanding the
@@ -591,7 +601,7 @@ you allow nested rcu_read_lock() calls, you can deadlock.
However, it is probably the easiest implementation to relate to, so is
a good starting point.
-It is extremely simple:
+It is extremely simple::
static DEFINE_RWLOCK(rcu_gp_mutex);
@@ -614,7 +624,7 @@ It is extremely simple:
[You can ignore rcu_assign_pointer() and rcu_dereference() without missing
much. But here are simplified versions anyway. And whatever you do,
-don't forget about them when submitting patches making use of RCU!]
+don't forget about them when submitting patches making use of RCU!]::
#define rcu_assign_pointer(p, v) \
({ \
@@ -659,6 +669,7 @@ This section presents a "toy" RCU implementation that is based on
on features such as hotplug CPU and the ability to run in CONFIG_PREEMPT
kernels. The definitions of rcu_dereference() and rcu_assign_pointer()
are the same as those shown in the preceding section, so they are omitted.
+::
void rcu_read_lock(void) { }
@@ -707,10 +718,12 @@ Quick Quiz #3: If it is illegal to block in an RCU read-side
6. ANALOGY WITH READER-WRITER LOCKING
+--------------------------------------
Although RCU can be used in many different ways, a very common use of
RCU is analogous to reader-writer locking. The following unified
diff shows how closely related RCU and reader-writer locking can be.
+::
@@ -5,5 +5,5 @@ struct el {
int data;
@@ -762,7 +775,7 @@ diff shows how closely related RCU and reader-writer locking can be.
return 0;
}
-Or, for those who prefer a side-by-side listing:
+Or, for those who prefer a side-by-side listing::
1 struct el { 1 struct el {
2 struct list_head list; 2 struct list_head list;
@@ -774,40 +787,44 @@ Or, for those who prefer a side-by-side listing:
8 rwlock_t listmutex; 8 spinlock_t listmutex;
9 struct el head; 9 struct el head;
- 1 int search(long key, int *result) 1 int search(long key, int *result)
- 2 { 2 {
- 3 struct list_head *lp; 3 struct list_head *lp;
- 4 struct el *p; 4 struct el *p;
- 5 5
- 6 read_lock(&listmutex); 6 rcu_read_lock();
- 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p, head, lp) {
- 8 if (p->key == key) { 8 if (p->key == key) {
- 9 *result = p->data; 9 *result = p->data;
-10 read_unlock(&listmutex); 10 rcu_read_unlock();
-11 return 1; 11 return 1;
-12 } 12 }
-13 } 13 }
-14 read_unlock(&listmutex); 14 rcu_read_unlock();
-15 return 0; 15 return 0;
-16 } 16 }
-
- 1 int delete(long key) 1 int delete(long key)
- 2 { 2 {
- 3 struct el *p; 3 struct el *p;
- 4 4
- 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
- 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p, head, lp) {
- 7 if (p->key == key) { 7 if (p->key == key) {
- 8 list_del(&p->list); 8 list_del_rcu(&p->list);
- 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
- 10 synchronize_rcu();
-10 kfree(p); 11 kfree(p);
-11 return 1; 12 return 1;
-12 } 13 }
-13 } 14 }
-14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
-15 return 0; 16 return 0;
-16 } 17 }
+::
+
+ 1 int search(long key, int *result) 1 int search(long key, int *result)
+ 2 { 2 {
+ 3 struct list_head *lp; 3 struct list_head *lp;
+ 4 struct el *p; 4 struct el *p;
+ 5 5
+ 6 read_lock(&listmutex); 6 rcu_read_lock();
+ 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p, head, lp) {
+ 8 if (p->key == key) { 8 if (p->key == key) {
+ 9 *result = p->data; 9 *result = p->data;
+ 10 read_unlock(&listmutex); 10 rcu_read_unlock();
+ 11 return 1; 11 return 1;
+ 12 } 12 }
+ 13 } 13 }
+ 14 read_unlock(&listmutex); 14 rcu_read_unlock();
+ 15 return 0; 15 return 0;
+ 16 } 16 }
+
+::
+
+ 1 int delete(long key) 1 int delete(long key)
+ 2 { 2 {
+ 3 struct el *p; 3 struct el *p;
+ 4 4
+ 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
+ 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p, head, lp) {
+ 7 if (p->key == key) { 7 if (p->key == key) {
+ 8 list_del(&p->list); 8 list_del_rcu(&p->list);
+ 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
+ 10 synchronize_rcu();
+ 10 kfree(p); 11 kfree(p);
+ 11 return 1; 12 return 1;
+ 12 } 13 }
+ 13 } 14 }
+ 14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
+ 15 return 0; 16 return 0;
+ 16 } 17 }
Either way, the differences are quite small. Read-side locking moves
to rcu_read_lock() and rcu_read_unlock, update-side locking moves from
@@ -827,13 +844,14 @@ be used in place of synchronize_rcu().
7. FULL LIST OF RCU APIs
+-------------------------
The RCU APIs are documented in docbook-format header comments in the
Linux-kernel source code, but it helps to have a full list of the
APIs, since there does not appear to be a way to categorize them
in docbook. Here is the list, by category.
-RCU list traversal:
+RCU list traversal::
list_entry_rcu
list_first_entry_rcu
@@ -854,7 +872,7 @@ RCU list traversal:
hlist_bl_first_rcu
hlist_bl_for_each_entry_rcu
-RCU pointer/list update:
+RCU pointer/list udate::
rcu_assign_pointer
list_add_rcu
@@ -876,7 +894,9 @@ RCU pointer/list update:
hlist_bl_del_rcu
hlist_bl_set_first_rcu
-RCU: Critical sections Grace period Barrier
+RCU::
+
+ Critical sections Grace period Barrier
rcu_read_lock synchronize_net rcu_barrier
rcu_read_unlock synchronize_rcu
@@ -885,7 +905,9 @@ RCU: Critical sections Grace period Barrier
rcu_dereference_check kfree_rcu
rcu_dereference_protected
-bh: Critical sections Grace period Barrier
+bh::
+
+ Critical sections Grace period Barrier
rcu_read_lock_bh call_rcu rcu_barrier
rcu_read_unlock_bh synchronize_rcu
@@ -896,7 +918,9 @@ bh: Critical sections Grace period Barrier
rcu_dereference_bh_protected
rcu_read_lock_bh_held
-sched: Critical sections Grace period Barrier
+sched::
+
+ Critical sections Grace period Barrier
rcu_read_lock_sched call_rcu rcu_barrier
rcu_read_unlock_sched synchronize_rcu
@@ -910,7 +934,9 @@ sched: Critical sections Grace period Barrier
rcu_read_lock_sched_held
-SRCU: Critical sections Grace period Barrier
+SRCU::
+
+ Critical sections Grace period Barrier
srcu_read_lock call_srcu srcu_barrier
srcu_read_unlock synchronize_srcu
@@ -918,13 +944,14 @@ SRCU: Critical sections Grace period Barrier
srcu_dereference_check
srcu_read_lock_held
-SRCU: Initialization/cleanup
+SRCU: Initialization/cleanup::
+
DEFINE_SRCU
DEFINE_STATIC_SRCU
init_srcu_struct
cleanup_srcu_struct
-All: lockdep-checked RCU-protected pointer access
+All: lockdep-checked RCU-protected pointer access::
rcu_access_pointer
rcu_dereference_raw
@@ -976,6 +1003,7 @@ the right tool for your job.
8. ANSWERS TO QUICK QUIZZES
+----------------------------
Quick Quiz #1: Why is this argument naive? How could a deadlock
occur when using this algorithm in a real-world Linux
--
2.20.1
^ permalink raw reply related [flat|nested] 23+ messages in thread
* [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-10-30 23:31 [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst tranmanphong
@ 2019-10-30 23:31 ` Phong Tran
2019-10-31 22:54 ` paulmck
2019-11-02 8:31 ` madhuparnabhowmik04
2 siblings, 0 replies; 23+ messages in thread
From: Phong Tran @ 2019-10-30 23:31 UTC (permalink / raw)
Sync the format with current state of kernel documentation.
This change base on rcu-dev branch
what changed:
- Format bullet lists
- Add literal blocks
Signed-off-by: Phong Tran <tranmanphong at gmail.com>
---
Documentation/RCU/index.rst | 1 +
.../RCU/{whatisRCU.txt => whatisRCU.rst} | 150 +++++++++++-------
2 files changed, 90 insertions(+), 61 deletions(-)
rename Documentation/RCU/{whatisRCU.txt => whatisRCU.rst} (91%)
diff --git a/Documentation/RCU/index.rst b/Documentation/RCU/index.rst
index 627128c230dc..b9b11481c727 100644
--- a/Documentation/RCU/index.rst
+++ b/Documentation/RCU/index.rst
@@ -8,6 +8,7 @@ RCU concepts
:maxdepth: 3
arrayRCU
+ whatisRCU
rcu
listRCU
NMI-RCU
diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.rst
similarity index 91%
rename from Documentation/RCU/whatisRCU.txt
rename to Documentation/RCU/whatisRCU.rst
index 58ba05c4d97f..70d0e4c21917 100644
--- a/Documentation/RCU/whatisRCU.txt
+++ b/Documentation/RCU/whatisRCU.rst
@@ -1,15 +1,18 @@
+.. _rcu_doc:
+
What is RCU? -- "Read, Copy, Update"
+======================================
Please note that the "What is RCU?" LWN series is an excellent place
to start learning about RCU:
-1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
-2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
-3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
-4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
- 2010 Big API Table http://lwn.net/Articles/419086/
-5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
- 2014 Big API Table http://lwn.net/Articles/609973/
+| 1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
+| 2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
+| 3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
+| 4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
+| 2010 Big API Table http://lwn.net/Articles/419086/
+| 5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
+| 2014 Big API Table http://lwn.net/Articles/609973/
What is RCU?
@@ -51,6 +54,7 @@ never need this document anyway. ;-)
1. RCU OVERVIEW
+----------------
The basic idea behind RCU is to split updates into "removal" and
"reclamation" phases. The removal phase removes references to data items
@@ -118,6 +122,7 @@ Read on to learn about how RCU's API makes this easy.
2. WHAT IS RCU'S CORE API?
+---------------------------
The core RCU API is quite small:
@@ -166,7 +171,7 @@ synchronize_rcu()
read-side critical sections on all CPUs have completed.
Note that synchronize_rcu() will -not- necessarily wait for
any subsequent RCU read-side critical sections to complete.
- For example, consider the following sequence of events:
+ For example, consider the following sequence of events::
CPU 0 CPU 1 CPU 2
----------------- ------------------------- ---------------
@@ -248,13 +253,13 @@ rcu_dereference()
Common coding practice uses rcu_dereference() to copy an
RCU-protected pointer to a local variable, then dereferences
- this local variable, for example as follows:
+ this local variable, for example as follows::
p = rcu_dereference(head.next);
return p->data;
However, in this case, one could just as easily combine these
- into one statement:
+ into one statement::
return rcu_dereference(head.next)->data;
@@ -267,7 +272,7 @@ rcu_dereference()
Note that the value returned by rcu_dereference() is valid
only within the enclosing RCU read-side critical section [1].
- For example, the following is -not- legal:
+ For example, the following is -not- legal::
rcu_read_lock();
p = rcu_dereference(head.next);
@@ -315,6 +320,7 @@ rcu_dereference()
The following diagram shows how each API communicates among the
reader, updater, and reclaimer.
+::
rcu_assign_pointer()
@@ -377,10 +383,12 @@ for specialized uses, but are relatively uncommon.
3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
+-----------------------------------------------
This section shows a simple use of the core RCU API to protect a
global pointer to a dynamically allocated structure. More-typical
uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt.
+::
struct foo {
int a;
@@ -467,13 +475,14 @@ arrayRCU.txt, and NMI-RCU.txt.
4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
+--------------------------------------------
In the example above, foo_update_a() blocks until a grace period elapses.
This is quite simple, but in some cases one cannot afford to wait so
long -- there might be other high-priority work to be done.
In such cases, one uses call_rcu() rather than synchronize_rcu().
-The call_rcu() API is as follows:
+The call_rcu() API is as follows::
void call_rcu(struct rcu_head * head,
void (*func)(struct rcu_head *head));
@@ -481,7 +490,7 @@ The call_rcu() API is as follows:
This function invokes func(head) after a grace period has elapsed.
This invocation might happen from either softirq or process context,
so the function is not permitted to block. The foo struct needs to
-have an rcu_head structure added, perhaps as follows:
+have an rcu_head structure added, perhaps as follows::
struct foo {
int a;
@@ -490,7 +499,7 @@ have an rcu_head structure added, perhaps as follows:
struct rcu_head rcu;
};
-The foo_update_a() function might then be written as follows:
+The foo_update_a() function might then be written as follows::
/*
* Create a new struct foo that is the same as the one currently
@@ -520,7 +529,7 @@ The foo_update_a() function might then be written as follows:
call_rcu(&old_fp->rcu, foo_reclaim);
}
-The foo_reclaim() function might appear as follows:
+The foo_reclaim() function might appear as follows::
void foo_reclaim(struct rcu_head *rp)
{
@@ -552,7 +561,7 @@ o Use call_rcu() -after- removing a data element from an
If the callback for call_rcu() is not doing anything more than calling
kfree() on the structure, you can use kfree_rcu() instead of call_rcu()
-to avoid having to write your own callback:
+to avoid having to write your own callback::
kfree_rcu(old_fp, rcu);
@@ -560,6 +569,7 @@ Again, see checklist.txt for additional rules governing the use of RCU.
5. WHAT ARE SOME SIMPLE IMPLEMENTATIONS OF RCU?
+------------------------------------------------
One of the nice things about RCU is that it has extremely simple "toy"
implementations that are a good first step towards understanding the
@@ -591,7 +601,7 @@ you allow nested rcu_read_lock() calls, you can deadlock.
However, it is probably the easiest implementation to relate to, so is
a good starting point.
-It is extremely simple:
+It is extremely simple::
static DEFINE_RWLOCK(rcu_gp_mutex);
@@ -614,7 +624,7 @@ It is extremely simple:
[You can ignore rcu_assign_pointer() and rcu_dereference() without missing
much. But here are simplified versions anyway. And whatever you do,
-don't forget about them when submitting patches making use of RCU!]
+don't forget about them when submitting patches making use of RCU!]::
#define rcu_assign_pointer(p, v) \
({ \
@@ -659,6 +669,7 @@ This section presents a "toy" RCU implementation that is based on
on features such as hotplug CPU and the ability to run in CONFIG_PREEMPT
kernels. The definitions of rcu_dereference() and rcu_assign_pointer()
are the same as those shown in the preceding section, so they are omitted.
+::
void rcu_read_lock(void) { }
@@ -707,10 +718,12 @@ Quick Quiz #3: If it is illegal to block in an RCU read-side
6. ANALOGY WITH READER-WRITER LOCKING
+--------------------------------------
Although RCU can be used in many different ways, a very common use of
RCU is analogous to reader-writer locking. The following unified
diff shows how closely related RCU and reader-writer locking can be.
+::
@@ -5,5 +5,5 @@ struct el {
int data;
@@ -762,7 +775,7 @@ diff shows how closely related RCU and reader-writer locking can be.
return 0;
}
-Or, for those who prefer a side-by-side listing:
+Or, for those who prefer a side-by-side listing::
1 struct el { 1 struct el {
2 struct list_head list; 2 struct list_head list;
@@ -774,40 +787,44 @@ Or, for those who prefer a side-by-side listing:
8 rwlock_t listmutex; 8 spinlock_t listmutex;
9 struct el head; 9 struct el head;
- 1 int search(long key, int *result) 1 int search(long key, int *result)
- 2 { 2 {
- 3 struct list_head *lp; 3 struct list_head *lp;
- 4 struct el *p; 4 struct el *p;
- 5 5
- 6 read_lock(&listmutex); 6 rcu_read_lock();
- 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p, head, lp) {
- 8 if (p->key == key) { 8 if (p->key == key) {
- 9 *result = p->data; 9 *result = p->data;
-10 read_unlock(&listmutex); 10 rcu_read_unlock();
-11 return 1; 11 return 1;
-12 } 12 }
-13 } 13 }
-14 read_unlock(&listmutex); 14 rcu_read_unlock();
-15 return 0; 15 return 0;
-16 } 16 }
-
- 1 int delete(long key) 1 int delete(long key)
- 2 { 2 {
- 3 struct el *p; 3 struct el *p;
- 4 4
- 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
- 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p, head, lp) {
- 7 if (p->key == key) { 7 if (p->key == key) {
- 8 list_del(&p->list); 8 list_del_rcu(&p->list);
- 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
- 10 synchronize_rcu();
-10 kfree(p); 11 kfree(p);
-11 return 1; 12 return 1;
-12 } 13 }
-13 } 14 }
-14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
-15 return 0; 16 return 0;
-16 } 17 }
+::
+
+ 1 int search(long key, int *result) 1 int search(long key, int *result)
+ 2 { 2 {
+ 3 struct list_head *lp; 3 struct list_head *lp;
+ 4 struct el *p; 4 struct el *p;
+ 5 5
+ 6 read_lock(&listmutex); 6 rcu_read_lock();
+ 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p, head, lp) {
+ 8 if (p->key == key) { 8 if (p->key == key) {
+ 9 *result = p->data; 9 *result = p->data;
+ 10 read_unlock(&listmutex); 10 rcu_read_unlock();
+ 11 return 1; 11 return 1;
+ 12 } 12 }
+ 13 } 13 }
+ 14 read_unlock(&listmutex); 14 rcu_read_unlock();
+ 15 return 0; 15 return 0;
+ 16 } 16 }
+
+::
+
+ 1 int delete(long key) 1 int delete(long key)
+ 2 { 2 {
+ 3 struct el *p; 3 struct el *p;
+ 4 4
+ 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
+ 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p, head, lp) {
+ 7 if (p->key == key) { 7 if (p->key == key) {
+ 8 list_del(&p->list); 8 list_del_rcu(&p->list);
+ 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
+ 10 synchronize_rcu();
+ 10 kfree(p); 11 kfree(p);
+ 11 return 1; 12 return 1;
+ 12 } 13 }
+ 13 } 14 }
+ 14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
+ 15 return 0; 16 return 0;
+ 16 } 17 }
Either way, the differences are quite small. Read-side locking moves
to rcu_read_lock() and rcu_read_unlock, update-side locking moves from
@@ -827,13 +844,14 @@ be used in place of synchronize_rcu().
7. FULL LIST OF RCU APIs
+-------------------------
The RCU APIs are documented in docbook-format header comments in the
Linux-kernel source code, but it helps to have a full list of the
APIs, since there does not appear to be a way to categorize them
in docbook. Here is the list, by category.
-RCU list traversal:
+RCU list traversal::
list_entry_rcu
list_first_entry_rcu
@@ -854,7 +872,7 @@ RCU list traversal:
hlist_bl_first_rcu
hlist_bl_for_each_entry_rcu
-RCU pointer/list update:
+RCU pointer/list udate::
rcu_assign_pointer
list_add_rcu
@@ -876,7 +894,9 @@ RCU pointer/list update:
hlist_bl_del_rcu
hlist_bl_set_first_rcu
-RCU: Critical sections Grace period Barrier
+RCU::
+
+ Critical sections Grace period Barrier
rcu_read_lock synchronize_net rcu_barrier
rcu_read_unlock synchronize_rcu
@@ -885,7 +905,9 @@ RCU: Critical sections Grace period Barrier
rcu_dereference_check kfree_rcu
rcu_dereference_protected
-bh: Critical sections Grace period Barrier
+bh::
+
+ Critical sections Grace period Barrier
rcu_read_lock_bh call_rcu rcu_barrier
rcu_read_unlock_bh synchronize_rcu
@@ -896,7 +918,9 @@ bh: Critical sections Grace period Barrier
rcu_dereference_bh_protected
rcu_read_lock_bh_held
-sched: Critical sections Grace period Barrier
+sched::
+
+ Critical sections Grace period Barrier
rcu_read_lock_sched call_rcu rcu_barrier
rcu_read_unlock_sched synchronize_rcu
@@ -910,7 +934,9 @@ sched: Critical sections Grace period Barrier
rcu_read_lock_sched_held
-SRCU: Critical sections Grace period Barrier
+SRCU::
+
+ Critical sections Grace period Barrier
srcu_read_lock call_srcu srcu_barrier
srcu_read_unlock synchronize_srcu
@@ -918,13 +944,14 @@ SRCU: Critical sections Grace period Barrier
srcu_dereference_check
srcu_read_lock_held
-SRCU: Initialization/cleanup
+SRCU: Initialization/cleanup::
+
DEFINE_SRCU
DEFINE_STATIC_SRCU
init_srcu_struct
cleanup_srcu_struct
-All: lockdep-checked RCU-protected pointer access
+All: lockdep-checked RCU-protected pointer access::
rcu_access_pointer
rcu_dereference_raw
@@ -976,6 +1003,7 @@ the right tool for your job.
8. ANSWERS TO QUICK QUIZZES
+----------------------------
Quick Quiz #1: Why is this argument naive? How could a deadlock
occur when using this algorithm in a real-world Linux
--
2.20.1
^ permalink raw reply related [flat|nested] 23+ messages in thread
* [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-10-30 23:31 [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst tranmanphong
2019-10-30 23:31 ` Phong Tran
@ 2019-10-31 22:54 ` paulmck
2019-10-31 22:54 ` Paul E. McKenney
` (3 more replies)
2019-11-02 8:31 ` madhuparnabhowmik04
2 siblings, 4 replies; 23+ messages in thread
From: paulmck @ 2019-10-31 22:54 UTC (permalink / raw)
On Thu, Oct 31, 2019 at 06:31:28AM +0700, Phong Tran wrote:
> Sync the format with current state of kernel documentation.
> This change base on rcu-dev branch
> what changed:
> - Format bullet lists
> - Add literal blocks
>
> Signed-off-by: Phong Tran <tranmanphong at gmail.com>
Queued and pushed with updated subject line and commit log, thank you!
Could you and Madhuparna please review and test each other's
.rst-conversion patches?
Thanx, Paul
> ---
> Documentation/RCU/index.rst | 1 +
> .../RCU/{whatisRCU.txt => whatisRCU.rst} | 150 +++++++++++-------
> 2 files changed, 90 insertions(+), 61 deletions(-)
> rename Documentation/RCU/{whatisRCU.txt => whatisRCU.rst} (91%)
>
> diff --git a/Documentation/RCU/index.rst b/Documentation/RCU/index.rst
> index 627128c230dc..b9b11481c727 100644
> --- a/Documentation/RCU/index.rst
> +++ b/Documentation/RCU/index.rst
> @@ -8,6 +8,7 @@ RCU concepts
> :maxdepth: 3
>
> arrayRCU
> + whatisRCU
> rcu
> listRCU
> NMI-RCU
> diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.rst
> similarity index 91%
> rename from Documentation/RCU/whatisRCU.txt
> rename to Documentation/RCU/whatisRCU.rst
> index 58ba05c4d97f..70d0e4c21917 100644
> --- a/Documentation/RCU/whatisRCU.txt
> +++ b/Documentation/RCU/whatisRCU.rst
> @@ -1,15 +1,18 @@
> +.. _rcu_doc:
> +
> What is RCU? -- "Read, Copy, Update"
> +======================================
>
> Please note that the "What is RCU?" LWN series is an excellent place
> to start learning about RCU:
>
> -1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> -2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> -3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> -4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> - 2010 Big API Table http://lwn.net/Articles/419086/
> -5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> - 2014 Big API Table http://lwn.net/Articles/609973/
> +| 1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> +| 2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> +| 3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> +| 4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> +| 2010 Big API Table http://lwn.net/Articles/419086/
> +| 5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> +| 2014 Big API Table http://lwn.net/Articles/609973/
>
>
> What is RCU?
> @@ -51,6 +54,7 @@ never need this document anyway. ;-)
>
>
> 1. RCU OVERVIEW
> +----------------
>
> The basic idea behind RCU is to split updates into "removal" and
> "reclamation" phases. The removal phase removes references to data items
> @@ -118,6 +122,7 @@ Read on to learn about how RCU's API makes this easy.
>
>
> 2. WHAT IS RCU'S CORE API?
> +---------------------------
>
> The core RCU API is quite small:
>
> @@ -166,7 +171,7 @@ synchronize_rcu()
> read-side critical sections on all CPUs have completed.
> Note that synchronize_rcu() will -not- necessarily wait for
> any subsequent RCU read-side critical sections to complete.
> - For example, consider the following sequence of events:
> + For example, consider the following sequence of events::
>
> CPU 0 CPU 1 CPU 2
> ----------------- ------------------------- ---------------
> @@ -248,13 +253,13 @@ rcu_dereference()
>
> Common coding practice uses rcu_dereference() to copy an
> RCU-protected pointer to a local variable, then dereferences
> - this local variable, for example as follows:
> + this local variable, for example as follows::
>
> p = rcu_dereference(head.next);
> return p->data;
>
> However, in this case, one could just as easily combine these
> - into one statement:
> + into one statement::
>
> return rcu_dereference(head.next)->data;
>
> @@ -267,7 +272,7 @@ rcu_dereference()
>
> Note that the value returned by rcu_dereference() is valid
> only within the enclosing RCU read-side critical section [1].
> - For example, the following is -not- legal:
> + For example, the following is -not- legal::
>
> rcu_read_lock();
> p = rcu_dereference(head.next);
> @@ -315,6 +320,7 @@ rcu_dereference()
>
> The following diagram shows how each API communicates among the
> reader, updater, and reclaimer.
> +::
>
>
> rcu_assign_pointer()
> @@ -377,10 +383,12 @@ for specialized uses, but are relatively uncommon.
>
>
> 3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
> +-----------------------------------------------
>
> This section shows a simple use of the core RCU API to protect a
> global pointer to a dynamically allocated structure. More-typical
> uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt.
> +::
>
> struct foo {
> int a;
> @@ -467,13 +475,14 @@ arrayRCU.txt, and NMI-RCU.txt.
>
>
> 4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
> +--------------------------------------------
>
> In the example above, foo_update_a() blocks until a grace period elapses.
> This is quite simple, but in some cases one cannot afford to wait so
> long -- there might be other high-priority work to be done.
>
> In such cases, one uses call_rcu() rather than synchronize_rcu().
> -The call_rcu() API is as follows:
> +The call_rcu() API is as follows::
>
> void call_rcu(struct rcu_head * head,
> void (*func)(struct rcu_head *head));
> @@ -481,7 +490,7 @@ The call_rcu() API is as follows:
> This function invokes func(head) after a grace period has elapsed.
> This invocation might happen from either softirq or process context,
> so the function is not permitted to block. The foo struct needs to
> -have an rcu_head structure added, perhaps as follows:
> +have an rcu_head structure added, perhaps as follows::
>
> struct foo {
> int a;
> @@ -490,7 +499,7 @@ have an rcu_head structure added, perhaps as follows:
> struct rcu_head rcu;
> };
>
> -The foo_update_a() function might then be written as follows:
> +The foo_update_a() function might then be written as follows::
>
> /*
> * Create a new struct foo that is the same as the one currently
> @@ -520,7 +529,7 @@ The foo_update_a() function might then be written as follows:
> call_rcu(&old_fp->rcu, foo_reclaim);
> }
>
> -The foo_reclaim() function might appear as follows:
> +The foo_reclaim() function might appear as follows::
>
> void foo_reclaim(struct rcu_head *rp)
> {
> @@ -552,7 +561,7 @@ o Use call_rcu() -after- removing a data element from an
>
> If the callback for call_rcu() is not doing anything more than calling
> kfree() on the structure, you can use kfree_rcu() instead of call_rcu()
> -to avoid having to write your own callback:
> +to avoid having to write your own callback::
>
> kfree_rcu(old_fp, rcu);
>
> @@ -560,6 +569,7 @@ Again, see checklist.txt for additional rules governing the use of RCU.
>
>
> 5. WHAT ARE SOME SIMPLE IMPLEMENTATIONS OF RCU?
> +------------------------------------------------
>
> One of the nice things about RCU is that it has extremely simple "toy"
> implementations that are a good first step towards understanding the
> @@ -591,7 +601,7 @@ you allow nested rcu_read_lock() calls, you can deadlock.
> However, it is probably the easiest implementation to relate to, so is
> a good starting point.
>
> -It is extremely simple:
> +It is extremely simple::
>
> static DEFINE_RWLOCK(rcu_gp_mutex);
>
> @@ -614,7 +624,7 @@ It is extremely simple:
>
> [You can ignore rcu_assign_pointer() and rcu_dereference() without missing
> much. But here are simplified versions anyway. And whatever you do,
> -don't forget about them when submitting patches making use of RCU!]
> +don't forget about them when submitting patches making use of RCU!]::
>
> #define rcu_assign_pointer(p, v) \
> ({ \
> @@ -659,6 +669,7 @@ This section presents a "toy" RCU implementation that is based on
> on features such as hotplug CPU and the ability to run in CONFIG_PREEMPT
> kernels. The definitions of rcu_dereference() and rcu_assign_pointer()
> are the same as those shown in the preceding section, so they are omitted.
> +::
>
> void rcu_read_lock(void) { }
>
> @@ -707,10 +718,12 @@ Quick Quiz #3: If it is illegal to block in an RCU read-side
>
>
> 6. ANALOGY WITH READER-WRITER LOCKING
> +--------------------------------------
>
> Although RCU can be used in many different ways, a very common use of
> RCU is analogous to reader-writer locking. The following unified
> diff shows how closely related RCU and reader-writer locking can be.
> +::
>
> @@ -5,5 +5,5 @@ struct el {
> int data;
> @@ -762,7 +775,7 @@ diff shows how closely related RCU and reader-writer locking can be.
> return 0;
> }
>
> -Or, for those who prefer a side-by-side listing:
> +Or, for those who prefer a side-by-side listing::
>
> 1 struct el { 1 struct el {
> 2 struct list_head list; 2 struct list_head list;
> @@ -774,40 +787,44 @@ Or, for those who prefer a side-by-side listing:
> 8 rwlock_t listmutex; 8 spinlock_t listmutex;
> 9 struct el head; 9 struct el head;
>
> - 1 int search(long key, int *result) 1 int search(long key, int *result)
> - 2 { 2 {
> - 3 struct list_head *lp; 3 struct list_head *lp;
> - 4 struct el *p; 4 struct el *p;
> - 5 5
> - 6 read_lock(&listmutex); 6 rcu_read_lock();
> - 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p, head, lp) {
> - 8 if (p->key == key) { 8 if (p->key == key) {
> - 9 *result = p->data; 9 *result = p->data;
> -10 read_unlock(&listmutex); 10 rcu_read_unlock();
> -11 return 1; 11 return 1;
> -12 } 12 }
> -13 } 13 }
> -14 read_unlock(&listmutex); 14 rcu_read_unlock();
> -15 return 0; 15 return 0;
> -16 } 16 }
> -
> - 1 int delete(long key) 1 int delete(long key)
> - 2 { 2 {
> - 3 struct el *p; 3 struct el *p;
> - 4 4
> - 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> - 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p, head, lp) {
> - 7 if (p->key == key) { 7 if (p->key == key) {
> - 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> - 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
> - 10 synchronize_rcu();
> -10 kfree(p); 11 kfree(p);
> -11 return 1; 12 return 1;
> -12 } 13 }
> -13 } 14 }
> -14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> -15 return 0; 16 return 0;
> -16 } 17 }
> +::
> +
> + 1 int search(long key, int *result) 1 int search(long key, int *result)
> + 2 { 2 {
> + 3 struct list_head *lp; 3 struct list_head *lp;
> + 4 struct el *p; 4 struct el *p;
> + 5 5
> + 6 read_lock(&listmutex); 6 rcu_read_lock();
> + 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p, head, lp) {
> + 8 if (p->key == key) { 8 if (p->key == key) {
> + 9 *result = p->data; 9 *result = p->data;
> + 10 read_unlock(&listmutex); 10 rcu_read_unlock();
> + 11 return 1; 11 return 1;
> + 12 } 12 }
> + 13 } 13 }
> + 14 read_unlock(&listmutex); 14 rcu_read_unlock();
> + 15 return 0; 15 return 0;
> + 16 } 16 }
> +
> +::
> +
> + 1 int delete(long key) 1 int delete(long key)
> + 2 { 2 {
> + 3 struct el *p; 3 struct el *p;
> + 4 4
> + 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> + 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p, head, lp) {
> + 7 if (p->key == key) { 7 if (p->key == key) {
> + 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> + 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
> + 10 synchronize_rcu();
> + 10 kfree(p); 11 kfree(p);
> + 11 return 1; 12 return 1;
> + 12 } 13 }
> + 13 } 14 }
> + 14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> + 15 return 0; 16 return 0;
> + 16 } 17 }
>
> Either way, the differences are quite small. Read-side locking moves
> to rcu_read_lock() and rcu_read_unlock, update-side locking moves from
> @@ -827,13 +844,14 @@ be used in place of synchronize_rcu().
>
>
> 7. FULL LIST OF RCU APIs
> +-------------------------
>
> The RCU APIs are documented in docbook-format header comments in the
> Linux-kernel source code, but it helps to have a full list of the
> APIs, since there does not appear to be a way to categorize them
> in docbook. Here is the list, by category.
>
> -RCU list traversal:
> +RCU list traversal::
>
> list_entry_rcu
> list_first_entry_rcu
> @@ -854,7 +872,7 @@ RCU list traversal:
> hlist_bl_first_rcu
> hlist_bl_for_each_entry_rcu
>
> -RCU pointer/list update:
> +RCU pointer/list udate::
>
> rcu_assign_pointer
> list_add_rcu
> @@ -876,7 +894,9 @@ RCU pointer/list update:
> hlist_bl_del_rcu
> hlist_bl_set_first_rcu
>
> -RCU: Critical sections Grace period Barrier
> +RCU::
> +
> + Critical sections Grace period Barrier
>
> rcu_read_lock synchronize_net rcu_barrier
> rcu_read_unlock synchronize_rcu
> @@ -885,7 +905,9 @@ RCU: Critical sections Grace period Barrier
> rcu_dereference_check kfree_rcu
> rcu_dereference_protected
>
> -bh: Critical sections Grace period Barrier
> +bh::
> +
> + Critical sections Grace period Barrier
>
> rcu_read_lock_bh call_rcu rcu_barrier
> rcu_read_unlock_bh synchronize_rcu
> @@ -896,7 +918,9 @@ bh: Critical sections Grace period Barrier
> rcu_dereference_bh_protected
> rcu_read_lock_bh_held
>
> -sched: Critical sections Grace period Barrier
> +sched::
> +
> + Critical sections Grace period Barrier
>
> rcu_read_lock_sched call_rcu rcu_barrier
> rcu_read_unlock_sched synchronize_rcu
> @@ -910,7 +934,9 @@ sched: Critical sections Grace period Barrier
> rcu_read_lock_sched_held
>
>
> -SRCU: Critical sections Grace period Barrier
> +SRCU::
> +
> + Critical sections Grace period Barrier
>
> srcu_read_lock call_srcu srcu_barrier
> srcu_read_unlock synchronize_srcu
> @@ -918,13 +944,14 @@ SRCU: Critical sections Grace period Barrier
> srcu_dereference_check
> srcu_read_lock_held
>
> -SRCU: Initialization/cleanup
> +SRCU: Initialization/cleanup::
> +
> DEFINE_SRCU
> DEFINE_STATIC_SRCU
> init_srcu_struct
> cleanup_srcu_struct
>
> -All: lockdep-checked RCU-protected pointer access
> +All: lockdep-checked RCU-protected pointer access::
>
> rcu_access_pointer
> rcu_dereference_raw
> @@ -976,6 +1003,7 @@ the right tool for your job.
>
>
> 8. ANSWERS TO QUICK QUIZZES
> +----------------------------
>
> Quick Quiz #1: Why is this argument naive? How could a deadlock
> occur when using this algorithm in a real-world Linux
> --
> 2.20.1
>
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-10-31 22:54 ` paulmck
2019-10-31 22:54 ` Paul E. McKenney
@ 2019-10-31 22:54 ` Paul E. McKenney
2019-11-01 1:17 ` tranmanphong
2019-11-01 3:33 ` madhuparnabhowmik04
3 siblings, 0 replies; 23+ messages in thread
From: Paul E. McKenney @ 2019-10-31 22:54 UTC (permalink / raw)
On Thu, Oct 31, 2019 at 06:31:28AM +0700, Phong Tran wrote:
> Sync the format with current state of kernel documentation.
> This change base on rcu-dev branch
> what changed:
> - Format bullet lists
> - Add literal blocks
>
> Signed-off-by: Phong Tran <tranmanphong at gmail.com>
Queued and pushed with updated subject line and commit log, thank you!
Could you and Madhuparna please review and test each other's
.rst-conversion patches?
Thanx, Paul
> ---
> Documentation/RCU/index.rst | 1 +
> .../RCU/{whatisRCU.txt => whatisRCU.rst} | 150 +++++++++++-------
> 2 files changed, 90 insertions(+), 61 deletions(-)
> rename Documentation/RCU/{whatisRCU.txt => whatisRCU.rst} (91%)
>
> diff --git a/Documentation/RCU/index.rst b/Documentation/RCU/index.rst
> index 627128c230dc..b9b11481c727 100644
> --- a/Documentation/RCU/index.rst
> +++ b/Documentation/RCU/index.rst
> @@ -8,6 +8,7 @@ RCU concepts
> :maxdepth: 3
>
> arrayRCU
> + whatisRCU
> rcu
> listRCU
> NMI-RCU
> diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.rst
> similarity index 91%
> rename from Documentation/RCU/whatisRCU.txt
> rename to Documentation/RCU/whatisRCU.rst
> index 58ba05c4d97f..70d0e4c21917 100644
> --- a/Documentation/RCU/whatisRCU.txt
> +++ b/Documentation/RCU/whatisRCU.rst
> @@ -1,15 +1,18 @@
> +.. _rcu_doc:
> +
> What is RCU? -- "Read, Copy, Update"
> +======================================
>
> Please note that the "What is RCU?" LWN series is an excellent place
> to start learning about RCU:
>
> -1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> -2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> -3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> -4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> - 2010 Big API Table http://lwn.net/Articles/419086/
> -5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> - 2014 Big API Table http://lwn.net/Articles/609973/
> +| 1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> +| 2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> +| 3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> +| 4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> +| 2010 Big API Table http://lwn.net/Articles/419086/
> +| 5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> +| 2014 Big API Table http://lwn.net/Articles/609973/
>
>
> What is RCU?
> @@ -51,6 +54,7 @@ never need this document anyway. ;-)
>
>
> 1. RCU OVERVIEW
> +----------------
>
> The basic idea behind RCU is to split updates into "removal" and
> "reclamation" phases. The removal phase removes references to data items
> @@ -118,6 +122,7 @@ Read on to learn about how RCU's API makes this easy.
>
>
> 2. WHAT IS RCU'S CORE API?
> +---------------------------
>
> The core RCU API is quite small:
>
> @@ -166,7 +171,7 @@ synchronize_rcu()
> read-side critical sections on all CPUs have completed.
> Note that synchronize_rcu() will -not- necessarily wait for
> any subsequent RCU read-side critical sections to complete.
> - For example, consider the following sequence of events:
> + For example, consider the following sequence of events::
>
> CPU 0 CPU 1 CPU 2
> ----------------- ------------------------- ---------------
> @@ -248,13 +253,13 @@ rcu_dereference()
>
> Common coding practice uses rcu_dereference() to copy an
> RCU-protected pointer to a local variable, then dereferences
> - this local variable, for example as follows:
> + this local variable, for example as follows::
>
> p = rcu_dereference(head.next);
> return p->data;
>
> However, in this case, one could just as easily combine these
> - into one statement:
> + into one statement::
>
> return rcu_dereference(head.next)->data;
>
> @@ -267,7 +272,7 @@ rcu_dereference()
>
> Note that the value returned by rcu_dereference() is valid
> only within the enclosing RCU read-side critical section [1].
> - For example, the following is -not- legal:
> + For example, the following is -not- legal::
>
> rcu_read_lock();
> p = rcu_dereference(head.next);
> @@ -315,6 +320,7 @@ rcu_dereference()
>
> The following diagram shows how each API communicates among the
> reader, updater, and reclaimer.
> +::
>
>
> rcu_assign_pointer()
> @@ -377,10 +383,12 @@ for specialized uses, but are relatively uncommon.
>
>
> 3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
> +-----------------------------------------------
>
> This section shows a simple use of the core RCU API to protect a
> global pointer to a dynamically allocated structure. More-typical
> uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt.
> +::
>
> struct foo {
> int a;
> @@ -467,13 +475,14 @@ arrayRCU.txt, and NMI-RCU.txt.
>
>
> 4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
> +--------------------------------------------
>
> In the example above, foo_update_a() blocks until a grace period elapses.
> This is quite simple, but in some cases one cannot afford to wait so
> long -- there might be other high-priority work to be done.
>
> In such cases, one uses call_rcu() rather than synchronize_rcu().
> -The call_rcu() API is as follows:
> +The call_rcu() API is as follows::
>
> void call_rcu(struct rcu_head * head,
> void (*func)(struct rcu_head *head));
> @@ -481,7 +490,7 @@ The call_rcu() API is as follows:
> This function invokes func(head) after a grace period has elapsed.
> This invocation might happen from either softirq or process context,
> so the function is not permitted to block. The foo struct needs to
> -have an rcu_head structure added, perhaps as follows:
> +have an rcu_head structure added, perhaps as follows::
>
> struct foo {
> int a;
> @@ -490,7 +499,7 @@ have an rcu_head structure added, perhaps as follows:
> struct rcu_head rcu;
> };
>
> -The foo_update_a() function might then be written as follows:
> +The foo_update_a() function might then be written as follows::
>
> /*
> * Create a new struct foo that is the same as the one currently
> @@ -520,7 +529,7 @@ The foo_update_a() function might then be written as follows:
> call_rcu(&old_fp->rcu, foo_reclaim);
> }
>
> -The foo_reclaim() function might appear as follows:
> +The foo_reclaim() function might appear as follows::
>
> void foo_reclaim(struct rcu_head *rp)
> {
> @@ -552,7 +561,7 @@ o Use call_rcu() -after- removing a data element from an
>
> If the callback for call_rcu() is not doing anything more than calling
> kfree() on the structure, you can use kfree_rcu() instead of call_rcu()
> -to avoid having to write your own callback:
> +to avoid having to write your own callback::
>
> kfree_rcu(old_fp, rcu);
>
> @@ -560,6 +569,7 @@ Again, see checklist.txt for additional rules governing the use of RCU.
>
>
> 5. WHAT ARE SOME SIMPLE IMPLEMENTATIONS OF RCU?
> +------------------------------------------------
>
> One of the nice things about RCU is that it has extremely simple "toy"
> implementations that are a good first step towards understanding the
> @@ -591,7 +601,7 @@ you allow nested rcu_read_lock() calls, you can deadlock.
> However, it is probably the easiest implementation to relate to, so is
> a good starting point.
>
> -It is extremely simple:
> +It is extremely simple::
>
> static DEFINE_RWLOCK(rcu_gp_mutex);
>
> @@ -614,7 +624,7 @@ It is extremely simple:
>
> [You can ignore rcu_assign_pointer() and rcu_dereference() without missing
> much. But here are simplified versions anyway. And whatever you do,
> -don't forget about them when submitting patches making use of RCU!]
> +don't forget about them when submitting patches making use of RCU!]::
>
> #define rcu_assign_pointer(p, v) \
> ({ \
> @@ -659,6 +669,7 @@ This section presents a "toy" RCU implementation that is based on
> on features such as hotplug CPU and the ability to run in CONFIG_PREEMPT
> kernels. The definitions of rcu_dereference() and rcu_assign_pointer()
> are the same as those shown in the preceding section, so they are omitted.
> +::
>
> void rcu_read_lock(void) { }
>
> @@ -707,10 +718,12 @@ Quick Quiz #3: If it is illegal to block in an RCU read-side
>
>
> 6. ANALOGY WITH READER-WRITER LOCKING
> +--------------------------------------
>
> Although RCU can be used in many different ways, a very common use of
> RCU is analogous to reader-writer locking. The following unified
> diff shows how closely related RCU and reader-writer locking can be.
> +::
>
> @@ -5,5 +5,5 @@ struct el {
> int data;
> @@ -762,7 +775,7 @@ diff shows how closely related RCU and reader-writer locking can be.
> return 0;
> }
>
> -Or, for those who prefer a side-by-side listing:
> +Or, for those who prefer a side-by-side listing::
>
> 1 struct el { 1 struct el {
> 2 struct list_head list; 2 struct list_head list;
> @@ -774,40 +787,44 @@ Or, for those who prefer a side-by-side listing:
> 8 rwlock_t listmutex; 8 spinlock_t listmutex;
> 9 struct el head; 9 struct el head;
>
> - 1 int search(long key, int *result) 1 int search(long key, int *result)
> - 2 { 2 {
> - 3 struct list_head *lp; 3 struct list_head *lp;
> - 4 struct el *p; 4 struct el *p;
> - 5 5
> - 6 read_lock(&listmutex); 6 rcu_read_lock();
> - 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p, head, lp) {
> - 8 if (p->key == key) { 8 if (p->key == key) {
> - 9 *result = p->data; 9 *result = p->data;
> -10 read_unlock(&listmutex); 10 rcu_read_unlock();
> -11 return 1; 11 return 1;
> -12 } 12 }
> -13 } 13 }
> -14 read_unlock(&listmutex); 14 rcu_read_unlock();
> -15 return 0; 15 return 0;
> -16 } 16 }
> -
> - 1 int delete(long key) 1 int delete(long key)
> - 2 { 2 {
> - 3 struct el *p; 3 struct el *p;
> - 4 4
> - 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> - 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p, head, lp) {
> - 7 if (p->key == key) { 7 if (p->key == key) {
> - 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> - 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
> - 10 synchronize_rcu();
> -10 kfree(p); 11 kfree(p);
> -11 return 1; 12 return 1;
> -12 } 13 }
> -13 } 14 }
> -14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> -15 return 0; 16 return 0;
> -16 } 17 }
> +::
> +
> + 1 int search(long key, int *result) 1 int search(long key, int *result)
> + 2 { 2 {
> + 3 struct list_head *lp; 3 struct list_head *lp;
> + 4 struct el *p; 4 struct el *p;
> + 5 5
> + 6 read_lock(&listmutex); 6 rcu_read_lock();
> + 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p, head, lp) {
> + 8 if (p->key == key) { 8 if (p->key == key) {
> + 9 *result = p->data; 9 *result = p->data;
> + 10 read_unlock(&listmutex); 10 rcu_read_unlock();
> + 11 return 1; 11 return 1;
> + 12 } 12 }
> + 13 } 13 }
> + 14 read_unlock(&listmutex); 14 rcu_read_unlock();
> + 15 return 0; 15 return 0;
> + 16 } 16 }
> +
> +::
> +
> + 1 int delete(long key) 1 int delete(long key)
> + 2 { 2 {
> + 3 struct el *p; 3 struct el *p;
> + 4 4
> + 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> + 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p, head, lp) {
> + 7 if (p->key == key) { 7 if (p->key == key) {
> + 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> + 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
> + 10 synchronize_rcu();
> + 10 kfree(p); 11 kfree(p);
> + 11 return 1; 12 return 1;
> + 12 } 13 }
> + 13 } 14 }
> + 14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> + 15 return 0; 16 return 0;
> + 16 } 17 }
>
> Either way, the differences are quite small. Read-side locking moves
> to rcu_read_lock() and rcu_read_unlock, update-side locking moves from
> @@ -827,13 +844,14 @@ be used in place of synchronize_rcu().
>
>
> 7. FULL LIST OF RCU APIs
> +-------------------------
>
> The RCU APIs are documented in docbook-format header comments in the
> Linux-kernel source code, but it helps to have a full list of the
> APIs, since there does not appear to be a way to categorize them
> in docbook. Here is the list, by category.
>
> -RCU list traversal:
> +RCU list traversal::
>
> list_entry_rcu
> list_first_entry_rcu
> @@ -854,7 +872,7 @@ RCU list traversal:
> hlist_bl_first_rcu
> hlist_bl_for_each_entry_rcu
>
> -RCU pointer/list update:
> +RCU pointer/list udate::
>
> rcu_assign_pointer
> list_add_rcu
> @@ -876,7 +894,9 @@ RCU pointer/list update:
> hlist_bl_del_rcu
> hlist_bl_set_first_rcu
>
> -RCU: Critical sections Grace period Barrier
> +RCU::
> +
> + Critical sections Grace period Barrier
>
> rcu_read_lock synchronize_net rcu_barrier
> rcu_read_unlock synchronize_rcu
> @@ -885,7 +905,9 @@ RCU: Critical sections Grace period Barrier
> rcu_dereference_check kfree_rcu
> rcu_dereference_protected
>
> -bh: Critical sections Grace period Barrier
> +bh::
> +
> + Critical sections Grace period Barrier
>
> rcu_read_lock_bh call_rcu rcu_barrier
> rcu_read_unlock_bh synchronize_rcu
> @@ -896,7 +918,9 @@ bh: Critical sections Grace period Barrier
> rcu_dereference_bh_protected
> rcu_read_lock_bh_held
>
> -sched: Critical sections Grace period Barrier
> +sched::
> +
> + Critical sections Grace period Barrier
>
> rcu_read_lock_sched call_rcu rcu_barrier
> rcu_read_unlock_sched synchronize_rcu
> @@ -910,7 +934,9 @@ sched: Critical sections Grace period Barrier
> rcu_read_lock_sched_held
>
>
> -SRCU: Critical sections Grace period Barrier
> +SRCU::
> +
> + Critical sections Grace period Barrier
>
> srcu_read_lock call_srcu srcu_barrier
> srcu_read_unlock synchronize_srcu
> @@ -918,13 +944,14 @@ SRCU: Critical sections Grace period Barrier
> srcu_dereference_check
> srcu_read_lock_held
>
> -SRCU: Initialization/cleanup
> +SRCU: Initialization/cleanup::
> +
> DEFINE_SRCU
> DEFINE_STATIC_SRCU
> init_srcu_struct
> cleanup_srcu_struct
>
> -All: lockdep-checked RCU-protected pointer access
> +All: lockdep-checked RCU-protected pointer access::
>
> rcu_access_pointer
> rcu_dereference_raw
> @@ -976,6 +1003,7 @@ the right tool for your job.
>
>
> 8. ANSWERS TO QUICK QUIZZES
> +----------------------------
>
> Quick Quiz #1: Why is this argument naive? How could a deadlock
> occur when using this algorithm in a real-world Linux
> --
> 2.20.1
>
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-10-31 22:54 ` paulmck
@ 2019-10-31 22:54 ` Paul E. McKenney
2019-10-31 22:54 ` Paul E. McKenney
` (2 subsequent siblings)
3 siblings, 0 replies; 23+ messages in thread
From: Paul E. McKenney @ 2019-10-31 22:54 UTC (permalink / raw)
To: Phong Tran
Cc: corbet, linux-doc, jiangshanlai, josh, rostedt, linux-kernel,
rcu, mathieu.desnoyers, joel, linux-kernel-mentees
On Thu, Oct 31, 2019 at 06:31:28AM +0700, Phong Tran wrote:
> Sync the format with current state of kernel documentation.
> This change base on rcu-dev branch
> what changed:
> - Format bullet lists
> - Add literal blocks
>
> Signed-off-by: Phong Tran <tranmanphong@gmail.com>
Queued and pushed with updated subject line and commit log, thank you!
Could you and Madhuparna please review and test each other's
.rst-conversion patches?
Thanx, Paul
> ---
> Documentation/RCU/index.rst | 1 +
> .../RCU/{whatisRCU.txt => whatisRCU.rst} | 150 +++++++++++-------
> 2 files changed, 90 insertions(+), 61 deletions(-)
> rename Documentation/RCU/{whatisRCU.txt => whatisRCU.rst} (91%)
>
> diff --git a/Documentation/RCU/index.rst b/Documentation/RCU/index.rst
> index 627128c230dc..b9b11481c727 100644
> --- a/Documentation/RCU/index.rst
> +++ b/Documentation/RCU/index.rst
> @@ -8,6 +8,7 @@ RCU concepts
> :maxdepth: 3
>
> arrayRCU
> + whatisRCU
> rcu
> listRCU
> NMI-RCU
> diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.rst
> similarity index 91%
> rename from Documentation/RCU/whatisRCU.txt
> rename to Documentation/RCU/whatisRCU.rst
> index 58ba05c4d97f..70d0e4c21917 100644
> --- a/Documentation/RCU/whatisRCU.txt
> +++ b/Documentation/RCU/whatisRCU.rst
> @@ -1,15 +1,18 @@
> +.. _rcu_doc:
> +
> What is RCU? -- "Read, Copy, Update"
> +======================================
>
> Please note that the "What is RCU?" LWN series is an excellent place
> to start learning about RCU:
>
> -1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> -2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> -3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> -4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> - 2010 Big API Table http://lwn.net/Articles/419086/
> -5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> - 2014 Big API Table http://lwn.net/Articles/609973/
> +| 1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> +| 2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> +| 3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> +| 4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> +| 2010 Big API Table http://lwn.net/Articles/419086/
> +| 5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> +| 2014 Big API Table http://lwn.net/Articles/609973/
>
>
> What is RCU?
> @@ -51,6 +54,7 @@ never need this document anyway. ;-)
>
>
> 1. RCU OVERVIEW
> +----------------
>
> The basic idea behind RCU is to split updates into "removal" and
> "reclamation" phases. The removal phase removes references to data items
> @@ -118,6 +122,7 @@ Read on to learn about how RCU's API makes this easy.
>
>
> 2. WHAT IS RCU'S CORE API?
> +---------------------------
>
> The core RCU API is quite small:
>
> @@ -166,7 +171,7 @@ synchronize_rcu()
> read-side critical sections on all CPUs have completed.
> Note that synchronize_rcu() will -not- necessarily wait for
> any subsequent RCU read-side critical sections to complete.
> - For example, consider the following sequence of events:
> + For example, consider the following sequence of events::
>
> CPU 0 CPU 1 CPU 2
> ----------------- ------------------------- ---------------
> @@ -248,13 +253,13 @@ rcu_dereference()
>
> Common coding practice uses rcu_dereference() to copy an
> RCU-protected pointer to a local variable, then dereferences
> - this local variable, for example as follows:
> + this local variable, for example as follows::
>
> p = rcu_dereference(head.next);
> return p->data;
>
> However, in this case, one could just as easily combine these
> - into one statement:
> + into one statement::
>
> return rcu_dereference(head.next)->data;
>
> @@ -267,7 +272,7 @@ rcu_dereference()
>
> Note that the value returned by rcu_dereference() is valid
> only within the enclosing RCU read-side critical section [1].
> - For example, the following is -not- legal:
> + For example, the following is -not- legal::
>
> rcu_read_lock();
> p = rcu_dereference(head.next);
> @@ -315,6 +320,7 @@ rcu_dereference()
>
> The following diagram shows how each API communicates among the
> reader, updater, and reclaimer.
> +::
>
>
> rcu_assign_pointer()
> @@ -377,10 +383,12 @@ for specialized uses, but are relatively uncommon.
>
>
> 3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
> +-----------------------------------------------
>
> This section shows a simple use of the core RCU API to protect a
> global pointer to a dynamically allocated structure. More-typical
> uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt.
> +::
>
> struct foo {
> int a;
> @@ -467,13 +475,14 @@ arrayRCU.txt, and NMI-RCU.txt.
>
>
> 4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
> +--------------------------------------------
>
> In the example above, foo_update_a() blocks until a grace period elapses.
> This is quite simple, but in some cases one cannot afford to wait so
> long -- there might be other high-priority work to be done.
>
> In such cases, one uses call_rcu() rather than synchronize_rcu().
> -The call_rcu() API is as follows:
> +The call_rcu() API is as follows::
>
> void call_rcu(struct rcu_head * head,
> void (*func)(struct rcu_head *head));
> @@ -481,7 +490,7 @@ The call_rcu() API is as follows:
> This function invokes func(head) after a grace period has elapsed.
> This invocation might happen from either softirq or process context,
> so the function is not permitted to block. The foo struct needs to
> -have an rcu_head structure added, perhaps as follows:
> +have an rcu_head structure added, perhaps as follows::
>
> struct foo {
> int a;
> @@ -490,7 +499,7 @@ have an rcu_head structure added, perhaps as follows:
> struct rcu_head rcu;
> };
>
> -The foo_update_a() function might then be written as follows:
> +The foo_update_a() function might then be written as follows::
>
> /*
> * Create a new struct foo that is the same as the one currently
> @@ -520,7 +529,7 @@ The foo_update_a() function might then be written as follows:
> call_rcu(&old_fp->rcu, foo_reclaim);
> }
>
> -The foo_reclaim() function might appear as follows:
> +The foo_reclaim() function might appear as follows::
>
> void foo_reclaim(struct rcu_head *rp)
> {
> @@ -552,7 +561,7 @@ o Use call_rcu() -after- removing a data element from an
>
> If the callback for call_rcu() is not doing anything more than calling
> kfree() on the structure, you can use kfree_rcu() instead of call_rcu()
> -to avoid having to write your own callback:
> +to avoid having to write your own callback::
>
> kfree_rcu(old_fp, rcu);
>
> @@ -560,6 +569,7 @@ Again, see checklist.txt for additional rules governing the use of RCU.
>
>
> 5. WHAT ARE SOME SIMPLE IMPLEMENTATIONS OF RCU?
> +------------------------------------------------
>
> One of the nice things about RCU is that it has extremely simple "toy"
> implementations that are a good first step towards understanding the
> @@ -591,7 +601,7 @@ you allow nested rcu_read_lock() calls, you can deadlock.
> However, it is probably the easiest implementation to relate to, so is
> a good starting point.
>
> -It is extremely simple:
> +It is extremely simple::
>
> static DEFINE_RWLOCK(rcu_gp_mutex);
>
> @@ -614,7 +624,7 @@ It is extremely simple:
>
> [You can ignore rcu_assign_pointer() and rcu_dereference() without missing
> much. But here are simplified versions anyway. And whatever you do,
> -don't forget about them when submitting patches making use of RCU!]
> +don't forget about them when submitting patches making use of RCU!]::
>
> #define rcu_assign_pointer(p, v) \
> ({ \
> @@ -659,6 +669,7 @@ This section presents a "toy" RCU implementation that is based on
> on features such as hotplug CPU and the ability to run in CONFIG_PREEMPT
> kernels. The definitions of rcu_dereference() and rcu_assign_pointer()
> are the same as those shown in the preceding section, so they are omitted.
> +::
>
> void rcu_read_lock(void) { }
>
> @@ -707,10 +718,12 @@ Quick Quiz #3: If it is illegal to block in an RCU read-side
>
>
> 6. ANALOGY WITH READER-WRITER LOCKING
> +--------------------------------------
>
> Although RCU can be used in many different ways, a very common use of
> RCU is analogous to reader-writer locking. The following unified
> diff shows how closely related RCU and reader-writer locking can be.
> +::
>
> @@ -5,5 +5,5 @@ struct el {
> int data;
> @@ -762,7 +775,7 @@ diff shows how closely related RCU and reader-writer locking can be.
> return 0;
> }
>
> -Or, for those who prefer a side-by-side listing:
> +Or, for those who prefer a side-by-side listing::
>
> 1 struct el { 1 struct el {
> 2 struct list_head list; 2 struct list_head list;
> @@ -774,40 +787,44 @@ Or, for those who prefer a side-by-side listing:
> 8 rwlock_t listmutex; 8 spinlock_t listmutex;
> 9 struct el head; 9 struct el head;
>
> - 1 int search(long key, int *result) 1 int search(long key, int *result)
> - 2 { 2 {
> - 3 struct list_head *lp; 3 struct list_head *lp;
> - 4 struct el *p; 4 struct el *p;
> - 5 5
> - 6 read_lock(&listmutex); 6 rcu_read_lock();
> - 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p, head, lp) {
> - 8 if (p->key == key) { 8 if (p->key == key) {
> - 9 *result = p->data; 9 *result = p->data;
> -10 read_unlock(&listmutex); 10 rcu_read_unlock();
> -11 return 1; 11 return 1;
> -12 } 12 }
> -13 } 13 }
> -14 read_unlock(&listmutex); 14 rcu_read_unlock();
> -15 return 0; 15 return 0;
> -16 } 16 }
> -
> - 1 int delete(long key) 1 int delete(long key)
> - 2 { 2 {
> - 3 struct el *p; 3 struct el *p;
> - 4 4
> - 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> - 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p, head, lp) {
> - 7 if (p->key == key) { 7 if (p->key == key) {
> - 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> - 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
> - 10 synchronize_rcu();
> -10 kfree(p); 11 kfree(p);
> -11 return 1; 12 return 1;
> -12 } 13 }
> -13 } 14 }
> -14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> -15 return 0; 16 return 0;
> -16 } 17 }
> +::
> +
> + 1 int search(long key, int *result) 1 int search(long key, int *result)
> + 2 { 2 {
> + 3 struct list_head *lp; 3 struct list_head *lp;
> + 4 struct el *p; 4 struct el *p;
> + 5 5
> + 6 read_lock(&listmutex); 6 rcu_read_lock();
> + 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p, head, lp) {
> + 8 if (p->key == key) { 8 if (p->key == key) {
> + 9 *result = p->data; 9 *result = p->data;
> + 10 read_unlock(&listmutex); 10 rcu_read_unlock();
> + 11 return 1; 11 return 1;
> + 12 } 12 }
> + 13 } 13 }
> + 14 read_unlock(&listmutex); 14 rcu_read_unlock();
> + 15 return 0; 15 return 0;
> + 16 } 16 }
> +
> +::
> +
> + 1 int delete(long key) 1 int delete(long key)
> + 2 { 2 {
> + 3 struct el *p; 3 struct el *p;
> + 4 4
> + 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> + 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p, head, lp) {
> + 7 if (p->key == key) { 7 if (p->key == key) {
> + 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> + 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
> + 10 synchronize_rcu();
> + 10 kfree(p); 11 kfree(p);
> + 11 return 1; 12 return 1;
> + 12 } 13 }
> + 13 } 14 }
> + 14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> + 15 return 0; 16 return 0;
> + 16 } 17 }
>
> Either way, the differences are quite small. Read-side locking moves
> to rcu_read_lock() and rcu_read_unlock, update-side locking moves from
> @@ -827,13 +844,14 @@ be used in place of synchronize_rcu().
>
>
> 7. FULL LIST OF RCU APIs
> +-------------------------
>
> The RCU APIs are documented in docbook-format header comments in the
> Linux-kernel source code, but it helps to have a full list of the
> APIs, since there does not appear to be a way to categorize them
> in docbook. Here is the list, by category.
>
> -RCU list traversal:
> +RCU list traversal::
>
> list_entry_rcu
> list_first_entry_rcu
> @@ -854,7 +872,7 @@ RCU list traversal:
> hlist_bl_first_rcu
> hlist_bl_for_each_entry_rcu
>
> -RCU pointer/list update:
> +RCU pointer/list udate::
>
> rcu_assign_pointer
> list_add_rcu
> @@ -876,7 +894,9 @@ RCU pointer/list update:
> hlist_bl_del_rcu
> hlist_bl_set_first_rcu
>
> -RCU: Critical sections Grace period Barrier
> +RCU::
> +
> + Critical sections Grace period Barrier
>
> rcu_read_lock synchronize_net rcu_barrier
> rcu_read_unlock synchronize_rcu
> @@ -885,7 +905,9 @@ RCU: Critical sections Grace period Barrier
> rcu_dereference_check kfree_rcu
> rcu_dereference_protected
>
> -bh: Critical sections Grace period Barrier
> +bh::
> +
> + Critical sections Grace period Barrier
>
> rcu_read_lock_bh call_rcu rcu_barrier
> rcu_read_unlock_bh synchronize_rcu
> @@ -896,7 +918,9 @@ bh: Critical sections Grace period Barrier
> rcu_dereference_bh_protected
> rcu_read_lock_bh_held
>
> -sched: Critical sections Grace period Barrier
> +sched::
> +
> + Critical sections Grace period Barrier
>
> rcu_read_lock_sched call_rcu rcu_barrier
> rcu_read_unlock_sched synchronize_rcu
> @@ -910,7 +934,9 @@ sched: Critical sections Grace period Barrier
> rcu_read_lock_sched_held
>
>
> -SRCU: Critical sections Grace period Barrier
> +SRCU::
> +
> + Critical sections Grace period Barrier
>
> srcu_read_lock call_srcu srcu_barrier
> srcu_read_unlock synchronize_srcu
> @@ -918,13 +944,14 @@ SRCU: Critical sections Grace period Barrier
> srcu_dereference_check
> srcu_read_lock_held
>
> -SRCU: Initialization/cleanup
> +SRCU: Initialization/cleanup::
> +
> DEFINE_SRCU
> DEFINE_STATIC_SRCU
> init_srcu_struct
> cleanup_srcu_struct
>
> -All: lockdep-checked RCU-protected pointer access
> +All: lockdep-checked RCU-protected pointer access::
>
> rcu_access_pointer
> rcu_dereference_raw
> @@ -976,6 +1003,7 @@ the right tool for your job.
>
>
> 8. ANSWERS TO QUICK QUIZZES
> +----------------------------
>
> Quick Quiz #1: Why is this argument naive? How could a deadlock
> occur when using this algorithm in a real-world Linux
> --
> 2.20.1
>
_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-10-31 22:54 ` paulmck
2019-10-31 22:54 ` Paul E. McKenney
2019-10-31 22:54 ` Paul E. McKenney
@ 2019-11-01 1:17 ` tranmanphong
2019-11-01 1:17 ` Phong Tran
` (2 more replies)
2019-11-01 3:33 ` madhuparnabhowmik04
3 siblings, 3 replies; 23+ messages in thread
From: tranmanphong @ 2019-11-01 1:17 UTC (permalink / raw)
Hi Paul,
On 11/1/19 5:54 AM, Paul E. McKenney wrote:
> Could you and Madhuparna please review and test each other's
> .rst-conversion patches?
>
It's fine.
pull and "make SPHINXDIRS="RCU" htmldocs pdfdocs" rcu dev branch
without error or warning.
thanks,
Phong.
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-11-01 1:17 ` tranmanphong
2019-11-01 1:17 ` Phong Tran
@ 2019-11-01 1:17 ` Phong Tran
2019-11-01 7:53 ` paulmck
2 siblings, 0 replies; 23+ messages in thread
From: Phong Tran @ 2019-11-01 1:17 UTC (permalink / raw)
Hi Paul,
On 11/1/19 5:54 AM, Paul E. McKenney wrote:
> Could you and Madhuparna please review and test each other's
> .rst-conversion patches?
>
It's fine.
pull and "make SPHINXDIRS="RCU" htmldocs pdfdocs" rcu dev branch
without error or warning.
thanks,
Phong.
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-11-01 1:17 ` tranmanphong
@ 2019-11-01 1:17 ` Phong Tran
2019-11-01 1:17 ` Phong Tran
2019-11-01 7:53 ` paulmck
2 siblings, 0 replies; 23+ messages in thread
From: Phong Tran @ 2019-11-01 1:17 UTC (permalink / raw)
To: paulmck, madhuparnabhowmik04
Cc: corbet, linux-doc, jiangshanlai, josh, rostedt, linux-kernel,
rcu, mathieu.desnoyers, joel, linux-kernel-mentees
Hi Paul,
On 11/1/19 5:54 AM, Paul E. McKenney wrote:
> Could you and Madhuparna please review and test each other's
> .rst-conversion patches?
>
It's fine.
pull and "make SPHINXDIRS="RCU" htmldocs pdfdocs" rcu dev branch
without error or warning.
thanks,
Phong.
_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-10-31 22:54 ` paulmck
` (2 preceding siblings ...)
2019-11-01 1:17 ` tranmanphong
@ 2019-11-01 3:33 ` madhuparnabhowmik04
2019-11-01 3:33 ` Madhuparna Bhowmik
` (2 more replies)
3 siblings, 3 replies; 23+ messages in thread
From: madhuparnabhowmik04 @ 2019-11-01 3:33 UTC (permalink / raw)
On Fri, 1 Nov, 2019, 4:24 AM Paul E. McKenney, <paulmck at kernel.org> wrote:
> On Thu, Oct 31, 2019 at 06:31:28AM +0700, Phong Tran wrote:
> > Sync the format with current state of kernel documentation.
> > This change base on rcu-dev branch
> > what changed:
> > - Format bullet lists
> > - Add literal blocks
> >
> > Signed-off-by: Phong Tran <tranmanphong at gmail.com>
>
> Queued and pushed with updated subject line and commit log, thank you!
>
> Could you and Madhuparna please review and test each other's
> .rst-conversion patches?
>
Sure, I will do it.
Regards
Madhuparna
> Thanx, Paul
>
> > ---
> > Documentation/RCU/index.rst | 1 +
> > .../RCU/{whatisRCU.txt => whatisRCU.rst} | 150 +++++++++++-------
> > 2 files changed, 90 insertions(+), 61 deletions(-)
> > rename Documentation/RCU/{whatisRCU.txt => whatisRCU.rst} (91%)
> >
> > diff --git a/Documentation/RCU/index.rst b/Documentation/RCU/index.rst
> > index 627128c230dc..b9b11481c727 100644
> > --- a/Documentation/RCU/index.rst
> > +++ b/Documentation/RCU/index.rst
> > @@ -8,6 +8,7 @@ RCU concepts
> > :maxdepth: 3
> >
> > arrayRCU
> > + whatisRCU
> > rcu
> > listRCU
> > NMI-RCU
> > diff --git a/Documentation/RCU/whatisRCU.txt
> b/Documentation/RCU/whatisRCU.rst
> > similarity index 91%
> > rename from Documentation/RCU/whatisRCU.txt
> > rename to Documentation/RCU/whatisRCU.rst
> > index 58ba05c4d97f..70d0e4c21917 100644
> > --- a/Documentation/RCU/whatisRCU.txt
> > +++ b/Documentation/RCU/whatisRCU.rst
> > @@ -1,15 +1,18 @@
> > +.. _rcu_doc:
> > +
> > What is RCU? -- "Read, Copy, Update"
> > +======================================
> >
> > Please note that the "What is RCU?" LWN series is an excellent place
> > to start learning about RCU:
> >
> > -1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> > -2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> > -3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> > -4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> > - 2010 Big API Table http://lwn.net/Articles/419086/
> > -5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> > - 2014 Big API Table http://lwn.net/Articles/609973/
> > +| 1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> > +| 2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> > +| 3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> > +| 4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> > +| 2010 Big API Table http://lwn.net/Articles/419086/
> > +| 5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> > +| 2014 Big API Table http://lwn.net/Articles/609973/
> >
> >
> > What is RCU?
> > @@ -51,6 +54,7 @@ never need this document anyway. ;-)
> >
> >
> > 1. RCU OVERVIEW
> > +----------------
> >
> > The basic idea behind RCU is to split updates into "removal" and
> > "reclamation" phases. The removal phase removes references to data
> items
> > @@ -118,6 +122,7 @@ Read on to learn about how RCU's API makes this easy.
> >
> >
> > 2. WHAT IS RCU'S CORE API?
> > +---------------------------
> >
> > The core RCU API is quite small:
> >
> > @@ -166,7 +171,7 @@ synchronize_rcu()
> > read-side critical sections on all CPUs have completed.
> > Note that synchronize_rcu() will -not- necessarily wait for
> > any subsequent RCU read-side critical sections to complete.
> > - For example, consider the following sequence of events:
> > + For example, consider the following sequence of events::
> >
> > CPU 0 CPU 1 CPU 2
> > ----------------- ------------------------- ---------------
> > @@ -248,13 +253,13 @@ rcu_dereference()
> >
> > Common coding practice uses rcu_dereference() to copy an
> > RCU-protected pointer to a local variable, then dereferences
> > - this local variable, for example as follows:
> > + this local variable, for example as follows::
> >
> > p = rcu_dereference(head.next);
> > return p->data;
> >
> > However, in this case, one could just as easily combine these
> > - into one statement:
> > + into one statement::
> >
> > return rcu_dereference(head.next)->data;
> >
> > @@ -267,7 +272,7 @@ rcu_dereference()
> >
> > Note that the value returned by rcu_dereference() is valid
> > only within the enclosing RCU read-side critical section [1].
> > - For example, the following is -not- legal:
> > + For example, the following is -not- legal::
> >
> > rcu_read_lock();
> > p = rcu_dereference(head.next);
> > @@ -315,6 +320,7 @@ rcu_dereference()
> >
> > The following diagram shows how each API communicates among the
> > reader, updater, and reclaimer.
> > +::
> >
> >
> > rcu_assign_pointer()
> > @@ -377,10 +383,12 @@ for specialized uses, but are relatively uncommon.
> >
> >
> > 3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
> > +-----------------------------------------------
> >
> > This section shows a simple use of the core RCU API to protect a
> > global pointer to a dynamically allocated structure. More-typical
> > uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt.
> > +::
> >
> > struct foo {
> > int a;
> > @@ -467,13 +475,14 @@ arrayRCU.txt, and NMI-RCU.txt.
> >
> >
> > 4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
> > +--------------------------------------------
> >
> > In the example above, foo_update_a() blocks until a grace period
> elapses.
> > This is quite simple, but in some cases one cannot afford to wait so
> > long -- there might be other high-priority work to be done.
> >
> > In such cases, one uses call_rcu() rather than synchronize_rcu().
> > -The call_rcu() API is as follows:
> > +The call_rcu() API is as follows::
> >
> > void call_rcu(struct rcu_head * head,
> > void (*func)(struct rcu_head *head));
> > @@ -481,7 +490,7 @@ The call_rcu() API is as follows:
> > This function invokes func(head) after a grace period has elapsed.
> > This invocation might happen from either softirq or process context,
> > so the function is not permitted to block. The foo struct needs to
> > -have an rcu_head structure added, perhaps as follows:
> > +have an rcu_head structure added, perhaps as follows::
> >
> > struct foo {
> > int a;
> > @@ -490,7 +499,7 @@ have an rcu_head structure added, perhaps as follows:
> > struct rcu_head rcu;
> > };
> >
> > -The foo_update_a() function might then be written as follows:
> > +The foo_update_a() function might then be written as follows::
> >
> > /*
> > * Create a new struct foo that is the same as the one currently
> > @@ -520,7 +529,7 @@ The foo_update_a() function might then be written as
> follows:
> > call_rcu(&old_fp->rcu, foo_reclaim);
> > }
> >
> > -The foo_reclaim() function might appear as follows:
> > +The foo_reclaim() function might appear as follows::
> >
> > void foo_reclaim(struct rcu_head *rp)
> > {
> > @@ -552,7 +561,7 @@ o Use call_rcu() -after- removing a data element
> from an
> >
> > If the callback for call_rcu() is not doing anything more than calling
> > kfree() on the structure, you can use kfree_rcu() instead of call_rcu()
> > -to avoid having to write your own callback:
> > +to avoid having to write your own callback::
> >
> > kfree_rcu(old_fp, rcu);
> >
> > @@ -560,6 +569,7 @@ Again, see checklist.txt for additional rules
> governing the use of RCU.
> >
> >
> > 5. WHAT ARE SOME SIMPLE IMPLEMENTATIONS OF RCU?
> > +------------------------------------------------
> >
> > One of the nice things about RCU is that it has extremely simple "toy"
> > implementations that are a good first step towards understanding the
> > @@ -591,7 +601,7 @@ you allow nested rcu_read_lock() calls, you can
> deadlock.
> > However, it is probably the easiest implementation to relate to, so is
> > a good starting point.
> >
> > -It is extremely simple:
> > +It is extremely simple::
> >
> > static DEFINE_RWLOCK(rcu_gp_mutex);
> >
> > @@ -614,7 +624,7 @@ It is extremely simple:
> >
> > [You can ignore rcu_assign_pointer() and rcu_dereference() without
> missing
> > much. But here are simplified versions anyway. And whatever you do,
> > -don't forget about them when submitting patches making use of RCU!]
> > +don't forget about them when submitting patches making use of RCU!]::
> >
> > #define rcu_assign_pointer(p, v) \
> > ({ \
> > @@ -659,6 +669,7 @@ This section presents a "toy" RCU implementation
> that is based on
> > on features such as hotplug CPU and the ability to run in CONFIG_PREEMPT
> > kernels. The definitions of rcu_dereference() and rcu_assign_pointer()
> > are the same as those shown in the preceding section, so they are
> omitted.
> > +::
> >
> > void rcu_read_lock(void) { }
> >
> > @@ -707,10 +718,12 @@ Quick Quiz #3: If it is illegal to block in an
> RCU read-side
> >
> >
> > 6. ANALOGY WITH READER-WRITER LOCKING
> > +--------------------------------------
> >
> > Although RCU can be used in many different ways, a very common use of
> > RCU is analogous to reader-writer locking. The following unified
> > diff shows how closely related RCU and reader-writer locking can be.
> > +::
> >
> > @@ -5,5 +5,5 @@ struct el {
> > int data;
> > @@ -762,7 +775,7 @@ diff shows how closely related RCU and reader-writer
> locking can be.
> > return 0;
> > }
> >
> > -Or, for those who prefer a side-by-side listing:
> > +Or, for those who prefer a side-by-side listing::
> >
> > 1 struct el { 1 struct el {
> > 2 struct list_head list; 2 struct list_head list;
> > @@ -774,40 +787,44 @@ Or, for those who prefer a side-by-side listing:
> > 8 rwlock_t listmutex; 8 spinlock_t listmutex;
> > 9 struct el head; 9 struct el head;
> >
> > - 1 int search(long key, int *result) 1 int search(long key, int
> *result)
> > - 2 { 2 {
> > - 3 struct list_head *lp; 3 struct list_head *lp;
> > - 4 struct el *p; 4 struct el *p;
> > - 5 5
> > - 6 read_lock(&listmutex); 6 rcu_read_lock();
> > - 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
> head, lp) {
> > - 8 if (p->key == key) { 8 if (p->key == key) {
> > - 9 *result = p->data; 9 *result = p->data;
> > -10 read_unlock(&listmutex); 10 rcu_read_unlock();
> > -11 return 1; 11 return 1;
> > -12 } 12 }
> > -13 } 13 }
> > -14 read_unlock(&listmutex); 14 rcu_read_unlock();
> > -15 return 0; 15 return 0;
> > -16 } 16 }
> > -
> > - 1 int delete(long key) 1 int delete(long key)
> > - 2 { 2 {
> > - 3 struct el *p; 3 struct el *p;
> > - 4 4
> > - 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> > - 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p,
> head, lp) {
> > - 7 if (p->key == key) { 7 if (p->key == key) {
> > - 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> > - 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
> > - 10 synchronize_rcu();
> > -10 kfree(p); 11 kfree(p);
> > -11 return 1; 12 return 1;
> > -12 } 13 }
> > -13 } 14 }
> > -14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> > -15 return 0; 16 return 0;
> > -16 } 17 }
> > +::
> > +
> > + 1 int search(long key, int *result) 1 int search(long key, int
> *result)
> > + 2 { 2 {
> > + 3 struct list_head *lp; 3 struct list_head *lp;
> > + 4 struct el *p; 4 struct el *p;
> > + 5 5
> > + 6 read_lock(&listmutex); 6 rcu_read_lock();
> > + 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
> head, lp) {
> > + 8 if (p->key == key) { 8 if (p->key == key) {
> > + 9 *result = p->data; 9 *result = p->data;
> > + 10 read_unlock(&listmutex); 10 rcu_read_unlock();
> > + 11 return 1; 11 return 1;
> > + 12 } 12 }
> > + 13 } 13 }
> > + 14 read_unlock(&listmutex); 14 rcu_read_unlock();
> > + 15 return 0; 15 return 0;
> > + 16 } 16 }
> > +
> > +::
> > +
> > + 1 int delete(long key) 1 int delete(long key)
> > + 2 { 2 {
> > + 3 struct el *p; 3 struct el *p;
> > + 4 4
> > + 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> > + 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p,
> head, lp) {
> > + 7 if (p->key == key) { 7 if (p->key == key) {
> > + 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> > + 9 write_unlock(&listmutex); 9
> spin_unlock(&listmutex);
> > + 10 synchronize_rcu();
> > + 10 kfree(p); 11 kfree(p);
> > + 11 return 1; 12 return 1;
> > + 12 } 13 }
> > + 13 } 14 }
> > + 14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> > + 15 return 0; 16 return 0;
> > + 16 } 17 }
> >
> > Either way, the differences are quite small. Read-side locking moves
> > to rcu_read_lock() and rcu_read_unlock, update-side locking moves from
> > @@ -827,13 +844,14 @@ be used in place of synchronize_rcu().
> >
> >
> > 7. FULL LIST OF RCU APIs
> > +-------------------------
> >
> > The RCU APIs are documented in docbook-format header comments in the
> > Linux-kernel source code, but it helps to have a full list of the
> > APIs, since there does not appear to be a way to categorize them
> > in docbook. Here is the list, by category.
> >
> > -RCU list traversal:
> > +RCU list traversal::
> >
> > list_entry_rcu
> > list_first_entry_rcu
> > @@ -854,7 +872,7 @@ RCU list traversal:
> > hlist_bl_first_rcu
> > hlist_bl_for_each_entry_rcu
> >
> > -RCU pointer/list update:
> > +RCU pointer/list udate::
> >
> > rcu_assign_pointer
> > list_add_rcu
> > @@ -876,7 +894,9 @@ RCU pointer/list update:
> > hlist_bl_del_rcu
> > hlist_bl_set_first_rcu
> >
> > -RCU: Critical sections Grace period Barrier
> > +RCU::
> > +
> > + Critical sections Grace period Barrier
> >
> > rcu_read_lock synchronize_net rcu_barrier
> > rcu_read_unlock synchronize_rcu
> > @@ -885,7 +905,9 @@ RCU: Critical sections Grace period
> Barrier
> > rcu_dereference_check kfree_rcu
> > rcu_dereference_protected
> >
> > -bh: Critical sections Grace period Barrier
> > +bh::
> > +
> > + Critical sections Grace period Barrier
> >
> > rcu_read_lock_bh call_rcu rcu_barrier
> > rcu_read_unlock_bh synchronize_rcu
> > @@ -896,7 +918,9 @@ bh: Critical sections Grace period
> Barrier
> > rcu_dereference_bh_protected
> > rcu_read_lock_bh_held
> >
> > -sched: Critical sections Grace period Barrier
> > +sched::
> > +
> > + Critical sections Grace period Barrier
> >
> > rcu_read_lock_sched call_rcu rcu_barrier
> > rcu_read_unlock_sched synchronize_rcu
> > @@ -910,7 +934,9 @@ sched: Critical sections Grace period
> Barrier
> > rcu_read_lock_sched_held
> >
> >
> > -SRCU: Critical sections Grace period Barrier
> > +SRCU::
> > +
> > + Critical sections Grace period Barrier
> >
> > srcu_read_lock call_srcu srcu_barrier
> > srcu_read_unlock synchronize_srcu
> > @@ -918,13 +944,14 @@ SRCU: Critical sections Grace period
> Barrier
> > srcu_dereference_check
> > srcu_read_lock_held
> >
> > -SRCU: Initialization/cleanup
> > +SRCU: Initialization/cleanup::
> > +
> > DEFINE_SRCU
> > DEFINE_STATIC_SRCU
> > init_srcu_struct
> > cleanup_srcu_struct
> >
> > -All: lockdep-checked RCU-protected pointer access
> > +All: lockdep-checked RCU-protected pointer access::
> >
> > rcu_access_pointer
> > rcu_dereference_raw
> > @@ -976,6 +1003,7 @@ the right tool for your job.
> >
> >
> > 8. ANSWERS TO QUICK QUIZZES
> > +----------------------------
> >
> > Quick Quiz #1: Why is this argument naive? How could a deadlock
> > occur when using this algorithm in a real-world Linux
> > --
> > 2.20.1
> >
>
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* [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-11-01 3:33 ` madhuparnabhowmik04
@ 2019-11-01 3:33 ` Madhuparna Bhowmik
2019-11-01 3:33 ` Madhuparna Bhowmik
2019-11-01 7:53 ` paulmck
2 siblings, 0 replies; 23+ messages in thread
From: Madhuparna Bhowmik @ 2019-11-01 3:33 UTC (permalink / raw)
On Fri, 1 Nov, 2019, 4:24 AM Paul E. McKenney, <paulmck at kernel.org> wrote:
> On Thu, Oct 31, 2019 at 06:31:28AM +0700, Phong Tran wrote:
> > Sync the format with current state of kernel documentation.
> > This change base on rcu-dev branch
> > what changed:
> > - Format bullet lists
> > - Add literal blocks
> >
> > Signed-off-by: Phong Tran <tranmanphong at gmail.com>
>
> Queued and pushed with updated subject line and commit log, thank you!
>
> Could you and Madhuparna please review and test each other's
> .rst-conversion patches?
>
Sure, I will do it.
Regards
Madhuparna
> Thanx, Paul
>
> > ---
> > Documentation/RCU/index.rst | 1 +
> > .../RCU/{whatisRCU.txt => whatisRCU.rst} | 150 +++++++++++-------
> > 2 files changed, 90 insertions(+), 61 deletions(-)
> > rename Documentation/RCU/{whatisRCU.txt => whatisRCU.rst} (91%)
> >
> > diff --git a/Documentation/RCU/index.rst b/Documentation/RCU/index.rst
> > index 627128c230dc..b9b11481c727 100644
> > --- a/Documentation/RCU/index.rst
> > +++ b/Documentation/RCU/index.rst
> > @@ -8,6 +8,7 @@ RCU concepts
> > :maxdepth: 3
> >
> > arrayRCU
> > + whatisRCU
> > rcu
> > listRCU
> > NMI-RCU
> > diff --git a/Documentation/RCU/whatisRCU.txt
> b/Documentation/RCU/whatisRCU.rst
> > similarity index 91%
> > rename from Documentation/RCU/whatisRCU.txt
> > rename to Documentation/RCU/whatisRCU.rst
> > index 58ba05c4d97f..70d0e4c21917 100644
> > --- a/Documentation/RCU/whatisRCU.txt
> > +++ b/Documentation/RCU/whatisRCU.rst
> > @@ -1,15 +1,18 @@
> > +.. _rcu_doc:
> > +
> > What is RCU? -- "Read, Copy, Update"
> > +======================================
> >
> > Please note that the "What is RCU?" LWN series is an excellent place
> > to start learning about RCU:
> >
> > -1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> > -2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> > -3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> > -4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> > - 2010 Big API Table http://lwn.net/Articles/419086/
> > -5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> > - 2014 Big API Table http://lwn.net/Articles/609973/
> > +| 1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> > +| 2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> > +| 3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> > +| 4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> > +| 2010 Big API Table http://lwn.net/Articles/419086/
> > +| 5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> > +| 2014 Big API Table http://lwn.net/Articles/609973/
> >
> >
> > What is RCU?
> > @@ -51,6 +54,7 @@ never need this document anyway. ;-)
> >
> >
> > 1. RCU OVERVIEW
> > +----------------
> >
> > The basic idea behind RCU is to split updates into "removal" and
> > "reclamation" phases. The removal phase removes references to data
> items
> > @@ -118,6 +122,7 @@ Read on to learn about how RCU's API makes this easy.
> >
> >
> > 2. WHAT IS RCU'S CORE API?
> > +---------------------------
> >
> > The core RCU API is quite small:
> >
> > @@ -166,7 +171,7 @@ synchronize_rcu()
> > read-side critical sections on all CPUs have completed.
> > Note that synchronize_rcu() will -not- necessarily wait for
> > any subsequent RCU read-side critical sections to complete.
> > - For example, consider the following sequence of events:
> > + For example, consider the following sequence of events::
> >
> > CPU 0 CPU 1 CPU 2
> > ----------------- ------------------------- ---------------
> > @@ -248,13 +253,13 @@ rcu_dereference()
> >
> > Common coding practice uses rcu_dereference() to copy an
> > RCU-protected pointer to a local variable, then dereferences
> > - this local variable, for example as follows:
> > + this local variable, for example as follows::
> >
> > p = rcu_dereference(head.next);
> > return p->data;
> >
> > However, in this case, one could just as easily combine these
> > - into one statement:
> > + into one statement::
> >
> > return rcu_dereference(head.next)->data;
> >
> > @@ -267,7 +272,7 @@ rcu_dereference()
> >
> > Note that the value returned by rcu_dereference() is valid
> > only within the enclosing RCU read-side critical section [1].
> > - For example, the following is -not- legal:
> > + For example, the following is -not- legal::
> >
> > rcu_read_lock();
> > p = rcu_dereference(head.next);
> > @@ -315,6 +320,7 @@ rcu_dereference()
> >
> > The following diagram shows how each API communicates among the
> > reader, updater, and reclaimer.
> > +::
> >
> >
> > rcu_assign_pointer()
> > @@ -377,10 +383,12 @@ for specialized uses, but are relatively uncommon.
> >
> >
> > 3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
> > +-----------------------------------------------
> >
> > This section shows a simple use of the core RCU API to protect a
> > global pointer to a dynamically allocated structure. More-typical
> > uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt.
> > +::
> >
> > struct foo {
> > int a;
> > @@ -467,13 +475,14 @@ arrayRCU.txt, and NMI-RCU.txt.
> >
> >
> > 4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
> > +--------------------------------------------
> >
> > In the example above, foo_update_a() blocks until a grace period
> elapses.
> > This is quite simple, but in some cases one cannot afford to wait so
> > long -- there might be other high-priority work to be done.
> >
> > In such cases, one uses call_rcu() rather than synchronize_rcu().
> > -The call_rcu() API is as follows:
> > +The call_rcu() API is as follows::
> >
> > void call_rcu(struct rcu_head * head,
> > void (*func)(struct rcu_head *head));
> > @@ -481,7 +490,7 @@ The call_rcu() API is as follows:
> > This function invokes func(head) after a grace period has elapsed.
> > This invocation might happen from either softirq or process context,
> > so the function is not permitted to block. The foo struct needs to
> > -have an rcu_head structure added, perhaps as follows:
> > +have an rcu_head structure added, perhaps as follows::
> >
> > struct foo {
> > int a;
> > @@ -490,7 +499,7 @@ have an rcu_head structure added, perhaps as follows:
> > struct rcu_head rcu;
> > };
> >
> > -The foo_update_a() function might then be written as follows:
> > +The foo_update_a() function might then be written as follows::
> >
> > /*
> > * Create a new struct foo that is the same as the one currently
> > @@ -520,7 +529,7 @@ The foo_update_a() function might then be written as
> follows:
> > call_rcu(&old_fp->rcu, foo_reclaim);
> > }
> >
> > -The foo_reclaim() function might appear as follows:
> > +The foo_reclaim() function might appear as follows::
> >
> > void foo_reclaim(struct rcu_head *rp)
> > {
> > @@ -552,7 +561,7 @@ o Use call_rcu() -after- removing a data element
> from an
> >
> > If the callback for call_rcu() is not doing anything more than calling
> > kfree() on the structure, you can use kfree_rcu() instead of call_rcu()
> > -to avoid having to write your own callback:
> > +to avoid having to write your own callback::
> >
> > kfree_rcu(old_fp, rcu);
> >
> > @@ -560,6 +569,7 @@ Again, see checklist.txt for additional rules
> governing the use of RCU.
> >
> >
> > 5. WHAT ARE SOME SIMPLE IMPLEMENTATIONS OF RCU?
> > +------------------------------------------------
> >
> > One of the nice things about RCU is that it has extremely simple "toy"
> > implementations that are a good first step towards understanding the
> > @@ -591,7 +601,7 @@ you allow nested rcu_read_lock() calls, you can
> deadlock.
> > However, it is probably the easiest implementation to relate to, so is
> > a good starting point.
> >
> > -It is extremely simple:
> > +It is extremely simple::
> >
> > static DEFINE_RWLOCK(rcu_gp_mutex);
> >
> > @@ -614,7 +624,7 @@ It is extremely simple:
> >
> > [You can ignore rcu_assign_pointer() and rcu_dereference() without
> missing
> > much. But here are simplified versions anyway. And whatever you do,
> > -don't forget about them when submitting patches making use of RCU!]
> > +don't forget about them when submitting patches making use of RCU!]::
> >
> > #define rcu_assign_pointer(p, v) \
> > ({ \
> > @@ -659,6 +669,7 @@ This section presents a "toy" RCU implementation
> that is based on
> > on features such as hotplug CPU and the ability to run in CONFIG_PREEMPT
> > kernels. The definitions of rcu_dereference() and rcu_assign_pointer()
> > are the same as those shown in the preceding section, so they are
> omitted.
> > +::
> >
> > void rcu_read_lock(void) { }
> >
> > @@ -707,10 +718,12 @@ Quick Quiz #3: If it is illegal to block in an
> RCU read-side
> >
> >
> > 6. ANALOGY WITH READER-WRITER LOCKING
> > +--------------------------------------
> >
> > Although RCU can be used in many different ways, a very common use of
> > RCU is analogous to reader-writer locking. The following unified
> > diff shows how closely related RCU and reader-writer locking can be.
> > +::
> >
> > @@ -5,5 +5,5 @@ struct el {
> > int data;
> > @@ -762,7 +775,7 @@ diff shows how closely related RCU and reader-writer
> locking can be.
> > return 0;
> > }
> >
> > -Or, for those who prefer a side-by-side listing:
> > +Or, for those who prefer a side-by-side listing::
> >
> > 1 struct el { 1 struct el {
> > 2 struct list_head list; 2 struct list_head list;
> > @@ -774,40 +787,44 @@ Or, for those who prefer a side-by-side listing:
> > 8 rwlock_t listmutex; 8 spinlock_t listmutex;
> > 9 struct el head; 9 struct el head;
> >
> > - 1 int search(long key, int *result) 1 int search(long key, int
> *result)
> > - 2 { 2 {
> > - 3 struct list_head *lp; 3 struct list_head *lp;
> > - 4 struct el *p; 4 struct el *p;
> > - 5 5
> > - 6 read_lock(&listmutex); 6 rcu_read_lock();
> > - 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
> head, lp) {
> > - 8 if (p->key == key) { 8 if (p->key == key) {
> > - 9 *result = p->data; 9 *result = p->data;
> > -10 read_unlock(&listmutex); 10 rcu_read_unlock();
> > -11 return 1; 11 return 1;
> > -12 } 12 }
> > -13 } 13 }
> > -14 read_unlock(&listmutex); 14 rcu_read_unlock();
> > -15 return 0; 15 return 0;
> > -16 } 16 }
> > -
> > - 1 int delete(long key) 1 int delete(long key)
> > - 2 { 2 {
> > - 3 struct el *p; 3 struct el *p;
> > - 4 4
> > - 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> > - 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p,
> head, lp) {
> > - 7 if (p->key == key) { 7 if (p->key == key) {
> > - 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> > - 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
> > - 10 synchronize_rcu();
> > -10 kfree(p); 11 kfree(p);
> > -11 return 1; 12 return 1;
> > -12 } 13 }
> > -13 } 14 }
> > -14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> > -15 return 0; 16 return 0;
> > -16 } 17 }
> > +::
> > +
> > + 1 int search(long key, int *result) 1 int search(long key, int
> *result)
> > + 2 { 2 {
> > + 3 struct list_head *lp; 3 struct list_head *lp;
> > + 4 struct el *p; 4 struct el *p;
> > + 5 5
> > + 6 read_lock(&listmutex); 6 rcu_read_lock();
> > + 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
> head, lp) {
> > + 8 if (p->key == key) { 8 if (p->key == key) {
> > + 9 *result = p->data; 9 *result = p->data;
> > + 10 read_unlock(&listmutex); 10 rcu_read_unlock();
> > + 11 return 1; 11 return 1;
> > + 12 } 12 }
> > + 13 } 13 }
> > + 14 read_unlock(&listmutex); 14 rcu_read_unlock();
> > + 15 return 0; 15 return 0;
> > + 16 } 16 }
> > +
> > +::
> > +
> > + 1 int delete(long key) 1 int delete(long key)
> > + 2 { 2 {
> > + 3 struct el *p; 3 struct el *p;
> > + 4 4
> > + 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> > + 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p,
> head, lp) {
> > + 7 if (p->key == key) { 7 if (p->key == key) {
> > + 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> > + 9 write_unlock(&listmutex); 9
> spin_unlock(&listmutex);
> > + 10 synchronize_rcu();
> > + 10 kfree(p); 11 kfree(p);
> > + 11 return 1; 12 return 1;
> > + 12 } 13 }
> > + 13 } 14 }
> > + 14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> > + 15 return 0; 16 return 0;
> > + 16 } 17 }
> >
> > Either way, the differences are quite small. Read-side locking moves
> > to rcu_read_lock() and rcu_read_unlock, update-side locking moves from
> > @@ -827,13 +844,14 @@ be used in place of synchronize_rcu().
> >
> >
> > 7. FULL LIST OF RCU APIs
> > +-------------------------
> >
> > The RCU APIs are documented in docbook-format header comments in the
> > Linux-kernel source code, but it helps to have a full list of the
> > APIs, since there does not appear to be a way to categorize them
> > in docbook. Here is the list, by category.
> >
> > -RCU list traversal:
> > +RCU list traversal::
> >
> > list_entry_rcu
> > list_first_entry_rcu
> > @@ -854,7 +872,7 @@ RCU list traversal:
> > hlist_bl_first_rcu
> > hlist_bl_for_each_entry_rcu
> >
> > -RCU pointer/list update:
> > +RCU pointer/list udate::
> >
> > rcu_assign_pointer
> > list_add_rcu
> > @@ -876,7 +894,9 @@ RCU pointer/list update:
> > hlist_bl_del_rcu
> > hlist_bl_set_first_rcu
> >
> > -RCU: Critical sections Grace period Barrier
> > +RCU::
> > +
> > + Critical sections Grace period Barrier
> >
> > rcu_read_lock synchronize_net rcu_barrier
> > rcu_read_unlock synchronize_rcu
> > @@ -885,7 +905,9 @@ RCU: Critical sections Grace period
> Barrier
> > rcu_dereference_check kfree_rcu
> > rcu_dereference_protected
> >
> > -bh: Critical sections Grace period Barrier
> > +bh::
> > +
> > + Critical sections Grace period Barrier
> >
> > rcu_read_lock_bh call_rcu rcu_barrier
> > rcu_read_unlock_bh synchronize_rcu
> > @@ -896,7 +918,9 @@ bh: Critical sections Grace period
> Barrier
> > rcu_dereference_bh_protected
> > rcu_read_lock_bh_held
> >
> > -sched: Critical sections Grace period Barrier
> > +sched::
> > +
> > + Critical sections Grace period Barrier
> >
> > rcu_read_lock_sched call_rcu rcu_barrier
> > rcu_read_unlock_sched synchronize_rcu
> > @@ -910,7 +934,9 @@ sched: Critical sections Grace period
> Barrier
> > rcu_read_lock_sched_held
> >
> >
> > -SRCU: Critical sections Grace period Barrier
> > +SRCU::
> > +
> > + Critical sections Grace period Barrier
> >
> > srcu_read_lock call_srcu srcu_barrier
> > srcu_read_unlock synchronize_srcu
> > @@ -918,13 +944,14 @@ SRCU: Critical sections Grace period
> Barrier
> > srcu_dereference_check
> > srcu_read_lock_held
> >
> > -SRCU: Initialization/cleanup
> > +SRCU: Initialization/cleanup::
> > +
> > DEFINE_SRCU
> > DEFINE_STATIC_SRCU
> > init_srcu_struct
> > cleanup_srcu_struct
> >
> > -All: lockdep-checked RCU-protected pointer access
> > +All: lockdep-checked RCU-protected pointer access::
> >
> > rcu_access_pointer
> > rcu_dereference_raw
> > @@ -976,6 +1003,7 @@ the right tool for your job.
> >
> >
> > 8. ANSWERS TO QUICK QUIZZES
> > +----------------------------
> >
> > Quick Quiz #1: Why is this argument naive? How could a deadlock
> > occur when using this algorithm in a real-world Linux
> > --
> > 2.20.1
> >
>
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* Re: [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-11-01 3:33 ` madhuparnabhowmik04
2019-11-01 3:33 ` Madhuparna Bhowmik
@ 2019-11-01 3:33 ` Madhuparna Bhowmik
2019-11-01 7:53 ` paulmck
2 siblings, 0 replies; 23+ messages in thread
From: Madhuparna Bhowmik @ 2019-11-01 3:33 UTC (permalink / raw)
To: paulmck
Cc: corbet, linux-doc, jiangshanlai, josh, rostedt, linux-kernel,
rcu, mathieu.desnoyers, joel, linux-kernel-mentees
[-- Attachment #1.1: Type: text/plain, Size: 17989 bytes --]
On Fri, 1 Nov, 2019, 4:24 AM Paul E. McKenney, <paulmck@kernel.org> wrote:
> On Thu, Oct 31, 2019 at 06:31:28AM +0700, Phong Tran wrote:
> > Sync the format with current state of kernel documentation.
> > This change base on rcu-dev branch
> > what changed:
> > - Format bullet lists
> > - Add literal blocks
> >
> > Signed-off-by: Phong Tran <tranmanphong@gmail.com>
>
> Queued and pushed with updated subject line and commit log, thank you!
>
> Could you and Madhuparna please review and test each other's
> .rst-conversion patches?
>
Sure, I will do it.
Regards
Madhuparna
> Thanx, Paul
>
> > ---
> > Documentation/RCU/index.rst | 1 +
> > .../RCU/{whatisRCU.txt => whatisRCU.rst} | 150 +++++++++++-------
> > 2 files changed, 90 insertions(+), 61 deletions(-)
> > rename Documentation/RCU/{whatisRCU.txt => whatisRCU.rst} (91%)
> >
> > diff --git a/Documentation/RCU/index.rst b/Documentation/RCU/index.rst
> > index 627128c230dc..b9b11481c727 100644
> > --- a/Documentation/RCU/index.rst
> > +++ b/Documentation/RCU/index.rst
> > @@ -8,6 +8,7 @@ RCU concepts
> > :maxdepth: 3
> >
> > arrayRCU
> > + whatisRCU
> > rcu
> > listRCU
> > NMI-RCU
> > diff --git a/Documentation/RCU/whatisRCU.txt
> b/Documentation/RCU/whatisRCU.rst
> > similarity index 91%
> > rename from Documentation/RCU/whatisRCU.txt
> > rename to Documentation/RCU/whatisRCU.rst
> > index 58ba05c4d97f..70d0e4c21917 100644
> > --- a/Documentation/RCU/whatisRCU.txt
> > +++ b/Documentation/RCU/whatisRCU.rst
> > @@ -1,15 +1,18 @@
> > +.. _rcu_doc:
> > +
> > What is RCU? -- "Read, Copy, Update"
> > +======================================
> >
> > Please note that the "What is RCU?" LWN series is an excellent place
> > to start learning about RCU:
> >
> > -1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> > -2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> > -3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> > -4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> > - 2010 Big API Table http://lwn.net/Articles/419086/
> > -5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> > - 2014 Big API Table http://lwn.net/Articles/609973/
> > +| 1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> > +| 2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> > +| 3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> > +| 4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> > +| 2010 Big API Table http://lwn.net/Articles/419086/
> > +| 5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> > +| 2014 Big API Table http://lwn.net/Articles/609973/
> >
> >
> > What is RCU?
> > @@ -51,6 +54,7 @@ never need this document anyway. ;-)
> >
> >
> > 1. RCU OVERVIEW
> > +----------------
> >
> > The basic idea behind RCU is to split updates into "removal" and
> > "reclamation" phases. The removal phase removes references to data
> items
> > @@ -118,6 +122,7 @@ Read on to learn about how RCU's API makes this easy.
> >
> >
> > 2. WHAT IS RCU'S CORE API?
> > +---------------------------
> >
> > The core RCU API is quite small:
> >
> > @@ -166,7 +171,7 @@ synchronize_rcu()
> > read-side critical sections on all CPUs have completed.
> > Note that synchronize_rcu() will -not- necessarily wait for
> > any subsequent RCU read-side critical sections to complete.
> > - For example, consider the following sequence of events:
> > + For example, consider the following sequence of events::
> >
> > CPU 0 CPU 1 CPU 2
> > ----------------- ------------------------- ---------------
> > @@ -248,13 +253,13 @@ rcu_dereference()
> >
> > Common coding practice uses rcu_dereference() to copy an
> > RCU-protected pointer to a local variable, then dereferences
> > - this local variable, for example as follows:
> > + this local variable, for example as follows::
> >
> > p = rcu_dereference(head.next);
> > return p->data;
> >
> > However, in this case, one could just as easily combine these
> > - into one statement:
> > + into one statement::
> >
> > return rcu_dereference(head.next)->data;
> >
> > @@ -267,7 +272,7 @@ rcu_dereference()
> >
> > Note that the value returned by rcu_dereference() is valid
> > only within the enclosing RCU read-side critical section [1].
> > - For example, the following is -not- legal:
> > + For example, the following is -not- legal::
> >
> > rcu_read_lock();
> > p = rcu_dereference(head.next);
> > @@ -315,6 +320,7 @@ rcu_dereference()
> >
> > The following diagram shows how each API communicates among the
> > reader, updater, and reclaimer.
> > +::
> >
> >
> > rcu_assign_pointer()
> > @@ -377,10 +383,12 @@ for specialized uses, but are relatively uncommon.
> >
> >
> > 3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
> > +-----------------------------------------------
> >
> > This section shows a simple use of the core RCU API to protect a
> > global pointer to a dynamically allocated structure. More-typical
> > uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt.
> > +::
> >
> > struct foo {
> > int a;
> > @@ -467,13 +475,14 @@ arrayRCU.txt, and NMI-RCU.txt.
> >
> >
> > 4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
> > +--------------------------------------------
> >
> > In the example above, foo_update_a() blocks until a grace period
> elapses.
> > This is quite simple, but in some cases one cannot afford to wait so
> > long -- there might be other high-priority work to be done.
> >
> > In such cases, one uses call_rcu() rather than synchronize_rcu().
> > -The call_rcu() API is as follows:
> > +The call_rcu() API is as follows::
> >
> > void call_rcu(struct rcu_head * head,
> > void (*func)(struct rcu_head *head));
> > @@ -481,7 +490,7 @@ The call_rcu() API is as follows:
> > This function invokes func(head) after a grace period has elapsed.
> > This invocation might happen from either softirq or process context,
> > so the function is not permitted to block. The foo struct needs to
> > -have an rcu_head structure added, perhaps as follows:
> > +have an rcu_head structure added, perhaps as follows::
> >
> > struct foo {
> > int a;
> > @@ -490,7 +499,7 @@ have an rcu_head structure added, perhaps as follows:
> > struct rcu_head rcu;
> > };
> >
> > -The foo_update_a() function might then be written as follows:
> > +The foo_update_a() function might then be written as follows::
> >
> > /*
> > * Create a new struct foo that is the same as the one currently
> > @@ -520,7 +529,7 @@ The foo_update_a() function might then be written as
> follows:
> > call_rcu(&old_fp->rcu, foo_reclaim);
> > }
> >
> > -The foo_reclaim() function might appear as follows:
> > +The foo_reclaim() function might appear as follows::
> >
> > void foo_reclaim(struct rcu_head *rp)
> > {
> > @@ -552,7 +561,7 @@ o Use call_rcu() -after- removing a data element
> from an
> >
> > If the callback for call_rcu() is not doing anything more than calling
> > kfree() on the structure, you can use kfree_rcu() instead of call_rcu()
> > -to avoid having to write your own callback:
> > +to avoid having to write your own callback::
> >
> > kfree_rcu(old_fp, rcu);
> >
> > @@ -560,6 +569,7 @@ Again, see checklist.txt for additional rules
> governing the use of RCU.
> >
> >
> > 5. WHAT ARE SOME SIMPLE IMPLEMENTATIONS OF RCU?
> > +------------------------------------------------
> >
> > One of the nice things about RCU is that it has extremely simple "toy"
> > implementations that are a good first step towards understanding the
> > @@ -591,7 +601,7 @@ you allow nested rcu_read_lock() calls, you can
> deadlock.
> > However, it is probably the easiest implementation to relate to, so is
> > a good starting point.
> >
> > -It is extremely simple:
> > +It is extremely simple::
> >
> > static DEFINE_RWLOCK(rcu_gp_mutex);
> >
> > @@ -614,7 +624,7 @@ It is extremely simple:
> >
> > [You can ignore rcu_assign_pointer() and rcu_dereference() without
> missing
> > much. But here are simplified versions anyway. And whatever you do,
> > -don't forget about them when submitting patches making use of RCU!]
> > +don't forget about them when submitting patches making use of RCU!]::
> >
> > #define rcu_assign_pointer(p, v) \
> > ({ \
> > @@ -659,6 +669,7 @@ This section presents a "toy" RCU implementation
> that is based on
> > on features such as hotplug CPU and the ability to run in CONFIG_PREEMPT
> > kernels. The definitions of rcu_dereference() and rcu_assign_pointer()
> > are the same as those shown in the preceding section, so they are
> omitted.
> > +::
> >
> > void rcu_read_lock(void) { }
> >
> > @@ -707,10 +718,12 @@ Quick Quiz #3: If it is illegal to block in an
> RCU read-side
> >
> >
> > 6. ANALOGY WITH READER-WRITER LOCKING
> > +--------------------------------------
> >
> > Although RCU can be used in many different ways, a very common use of
> > RCU is analogous to reader-writer locking. The following unified
> > diff shows how closely related RCU and reader-writer locking can be.
> > +::
> >
> > @@ -5,5 +5,5 @@ struct el {
> > int data;
> > @@ -762,7 +775,7 @@ diff shows how closely related RCU and reader-writer
> locking can be.
> > return 0;
> > }
> >
> > -Or, for those who prefer a side-by-side listing:
> > +Or, for those who prefer a side-by-side listing::
> >
> > 1 struct el { 1 struct el {
> > 2 struct list_head list; 2 struct list_head list;
> > @@ -774,40 +787,44 @@ Or, for those who prefer a side-by-side listing:
> > 8 rwlock_t listmutex; 8 spinlock_t listmutex;
> > 9 struct el head; 9 struct el head;
> >
> > - 1 int search(long key, int *result) 1 int search(long key, int
> *result)
> > - 2 { 2 {
> > - 3 struct list_head *lp; 3 struct list_head *lp;
> > - 4 struct el *p; 4 struct el *p;
> > - 5 5
> > - 6 read_lock(&listmutex); 6 rcu_read_lock();
> > - 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
> head, lp) {
> > - 8 if (p->key == key) { 8 if (p->key == key) {
> > - 9 *result = p->data; 9 *result = p->data;
> > -10 read_unlock(&listmutex); 10 rcu_read_unlock();
> > -11 return 1; 11 return 1;
> > -12 } 12 }
> > -13 } 13 }
> > -14 read_unlock(&listmutex); 14 rcu_read_unlock();
> > -15 return 0; 15 return 0;
> > -16 } 16 }
> > -
> > - 1 int delete(long key) 1 int delete(long key)
> > - 2 { 2 {
> > - 3 struct el *p; 3 struct el *p;
> > - 4 4
> > - 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> > - 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p,
> head, lp) {
> > - 7 if (p->key == key) { 7 if (p->key == key) {
> > - 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> > - 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
> > - 10 synchronize_rcu();
> > -10 kfree(p); 11 kfree(p);
> > -11 return 1; 12 return 1;
> > -12 } 13 }
> > -13 } 14 }
> > -14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> > -15 return 0; 16 return 0;
> > -16 } 17 }
> > +::
> > +
> > + 1 int search(long key, int *result) 1 int search(long key, int
> *result)
> > + 2 { 2 {
> > + 3 struct list_head *lp; 3 struct list_head *lp;
> > + 4 struct el *p; 4 struct el *p;
> > + 5 5
> > + 6 read_lock(&listmutex); 6 rcu_read_lock();
> > + 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
> head, lp) {
> > + 8 if (p->key == key) { 8 if (p->key == key) {
> > + 9 *result = p->data; 9 *result = p->data;
> > + 10 read_unlock(&listmutex); 10 rcu_read_unlock();
> > + 11 return 1; 11 return 1;
> > + 12 } 12 }
> > + 13 } 13 }
> > + 14 read_unlock(&listmutex); 14 rcu_read_unlock();
> > + 15 return 0; 15 return 0;
> > + 16 } 16 }
> > +
> > +::
> > +
> > + 1 int delete(long key) 1 int delete(long key)
> > + 2 { 2 {
> > + 3 struct el *p; 3 struct el *p;
> > + 4 4
> > + 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> > + 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p,
> head, lp) {
> > + 7 if (p->key == key) { 7 if (p->key == key) {
> > + 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> > + 9 write_unlock(&listmutex); 9
> spin_unlock(&listmutex);
> > + 10 synchronize_rcu();
> > + 10 kfree(p); 11 kfree(p);
> > + 11 return 1; 12 return 1;
> > + 12 } 13 }
> > + 13 } 14 }
> > + 14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> > + 15 return 0; 16 return 0;
> > + 16 } 17 }
> >
> > Either way, the differences are quite small. Read-side locking moves
> > to rcu_read_lock() and rcu_read_unlock, update-side locking moves from
> > @@ -827,13 +844,14 @@ be used in place of synchronize_rcu().
> >
> >
> > 7. FULL LIST OF RCU APIs
> > +-------------------------
> >
> > The RCU APIs are documented in docbook-format header comments in the
> > Linux-kernel source code, but it helps to have a full list of the
> > APIs, since there does not appear to be a way to categorize them
> > in docbook. Here is the list, by category.
> >
> > -RCU list traversal:
> > +RCU list traversal::
> >
> > list_entry_rcu
> > list_first_entry_rcu
> > @@ -854,7 +872,7 @@ RCU list traversal:
> > hlist_bl_first_rcu
> > hlist_bl_for_each_entry_rcu
> >
> > -RCU pointer/list update:
> > +RCU pointer/list udate::
> >
> > rcu_assign_pointer
> > list_add_rcu
> > @@ -876,7 +894,9 @@ RCU pointer/list update:
> > hlist_bl_del_rcu
> > hlist_bl_set_first_rcu
> >
> > -RCU: Critical sections Grace period Barrier
> > +RCU::
> > +
> > + Critical sections Grace period Barrier
> >
> > rcu_read_lock synchronize_net rcu_barrier
> > rcu_read_unlock synchronize_rcu
> > @@ -885,7 +905,9 @@ RCU: Critical sections Grace period
> Barrier
> > rcu_dereference_check kfree_rcu
> > rcu_dereference_protected
> >
> > -bh: Critical sections Grace period Barrier
> > +bh::
> > +
> > + Critical sections Grace period Barrier
> >
> > rcu_read_lock_bh call_rcu rcu_barrier
> > rcu_read_unlock_bh synchronize_rcu
> > @@ -896,7 +918,9 @@ bh: Critical sections Grace period
> Barrier
> > rcu_dereference_bh_protected
> > rcu_read_lock_bh_held
> >
> > -sched: Critical sections Grace period Barrier
> > +sched::
> > +
> > + Critical sections Grace period Barrier
> >
> > rcu_read_lock_sched call_rcu rcu_barrier
> > rcu_read_unlock_sched synchronize_rcu
> > @@ -910,7 +934,9 @@ sched: Critical sections Grace period
> Barrier
> > rcu_read_lock_sched_held
> >
> >
> > -SRCU: Critical sections Grace period Barrier
> > +SRCU::
> > +
> > + Critical sections Grace period Barrier
> >
> > srcu_read_lock call_srcu srcu_barrier
> > srcu_read_unlock synchronize_srcu
> > @@ -918,13 +944,14 @@ SRCU: Critical sections Grace period
> Barrier
> > srcu_dereference_check
> > srcu_read_lock_held
> >
> > -SRCU: Initialization/cleanup
> > +SRCU: Initialization/cleanup::
> > +
> > DEFINE_SRCU
> > DEFINE_STATIC_SRCU
> > init_srcu_struct
> > cleanup_srcu_struct
> >
> > -All: lockdep-checked RCU-protected pointer access
> > +All: lockdep-checked RCU-protected pointer access::
> >
> > rcu_access_pointer
> > rcu_dereference_raw
> > @@ -976,6 +1003,7 @@ the right tool for your job.
> >
> >
> > 8. ANSWERS TO QUICK QUIZZES
> > +----------------------------
> >
> > Quick Quiz #1: Why is this argument naive? How could a deadlock
> > occur when using this algorithm in a real-world Linux
> > --
> > 2.20.1
> >
>
[-- Attachment #1.2: Type: text/html, Size: 24707 bytes --]
[-- Attachment #2: Type: text/plain, Size: 201 bytes --]
_______________________________________________
Linux-kernel-mentees mailing list
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https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-11-01 1:17 ` tranmanphong
2019-11-01 1:17 ` Phong Tran
2019-11-01 1:17 ` Phong Tran
@ 2019-11-01 7:53 ` paulmck
2019-11-01 7:53 ` Paul E. McKenney
2019-11-01 7:53 ` Paul E. McKenney
2 siblings, 2 replies; 23+ messages in thread
From: paulmck @ 2019-11-01 7:53 UTC (permalink / raw)
On Fri, Nov 01, 2019 at 08:17:36AM +0700, Phong Tran wrote:
> Hi Paul,
> On 11/1/19 5:54 AM, Paul E. McKenney wrote:
> > Could you and Madhuparna please review and test each other's
> > .rst-conversion patches?
>
> It's fine.
> pull and "make SPHINXDIRS="RCU" htmldocs pdfdocs" rcu dev branch
> without error or warning.
Very good, thank you!
Once you have done that (or if you have already done that) and have
verified that the resulting .html and .pdf files for the changed portions
look good, you can respond with a Tested-by tag, which has "Tested-by:",
your name, and your email within "<" and ">". For example, commit
127068abe85b ("i2c: qcom-geni: Disable DMA processing on the Lenovo Yoga
C630") has this:
Tested-by: Bjorn Andersson <bjorn.andersson at linaro.org>
After you review the code, for example, by checking either the patch or the
resulting .rst file, you can respond with a very similar Reviewed-by tag.
Which allows you to get a start on participating in the code-review
process.
Thanx, Paul
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-11-01 7:53 ` paulmck
@ 2019-11-01 7:53 ` Paul E. McKenney
2019-11-01 7:53 ` Paul E. McKenney
1 sibling, 0 replies; 23+ messages in thread
From: Paul E. McKenney @ 2019-11-01 7:53 UTC (permalink / raw)
On Fri, Nov 01, 2019 at 08:17:36AM +0700, Phong Tran wrote:
> Hi Paul,
> On 11/1/19 5:54 AM, Paul E. McKenney wrote:
> > Could you and Madhuparna please review and test each other's
> > .rst-conversion patches?
>
> It's fine.
> pull and "make SPHINXDIRS="RCU" htmldocs pdfdocs" rcu dev branch
> without error or warning.
Very good, thank you!
Once you have done that (or if you have already done that) and have
verified that the resulting .html and .pdf files for the changed portions
look good, you can respond with a Tested-by tag, which has "Tested-by:",
your name, and your email within "<" and ">". For example, commit
127068abe85b ("i2c: qcom-geni: Disable DMA processing on the Lenovo Yoga
C630") has this:
Tested-by: Bjorn Andersson <bjorn.andersson at linaro.org>
After you review the code, for example, by checking either the patch or the
resulting .rst file, you can respond with a very similar Reviewed-by tag.
Which allows you to get a start on participating in the code-review
process.
Thanx, Paul
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-11-01 7:53 ` paulmck
2019-11-01 7:53 ` Paul E. McKenney
@ 2019-11-01 7:53 ` Paul E. McKenney
1 sibling, 0 replies; 23+ messages in thread
From: Paul E. McKenney @ 2019-11-01 7:53 UTC (permalink / raw)
To: Phong Tran
Cc: corbet, linux-doc, jiangshanlai, josh, rostedt, linux-kernel,
rcu, mathieu.desnoyers, joel, linux-kernel-mentees
On Fri, Nov 01, 2019 at 08:17:36AM +0700, Phong Tran wrote:
> Hi Paul,
> On 11/1/19 5:54 AM, Paul E. McKenney wrote:
> > Could you and Madhuparna please review and test each other's
> > .rst-conversion patches?
>
> It's fine.
> pull and "make SPHINXDIRS="RCU" htmldocs pdfdocs" rcu dev branch
> without error or warning.
Very good, thank you!
Once you have done that (or if you have already done that) and have
verified that the resulting .html and .pdf files for the changed portions
look good, you can respond with a Tested-by tag, which has "Tested-by:",
your name, and your email within "<" and ">". For example, commit
127068abe85b ("i2c: qcom-geni: Disable DMA processing on the Lenovo Yoga
C630") has this:
Tested-by: Bjorn Andersson <bjorn.andersson@linaro.org>
After you review the code, for example, by checking either the patch or the
resulting .rst file, you can respond with a very similar Reviewed-by tag.
Which allows you to get a start on participating in the code-review
process.
Thanx, Paul
_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-11-01 3:33 ` madhuparnabhowmik04
2019-11-01 3:33 ` Madhuparna Bhowmik
2019-11-01 3:33 ` Madhuparna Bhowmik
@ 2019-11-01 7:53 ` paulmck
2019-11-01 7:53 ` Paul E. McKenney
2019-11-01 7:53 ` Paul E. McKenney
2 siblings, 2 replies; 23+ messages in thread
From: paulmck @ 2019-11-01 7:53 UTC (permalink / raw)
On Fri, Nov 01, 2019 at 09:03:57AM +0530, Madhuparna Bhowmik wrote:
> On Fri, 1 Nov, 2019, 4:24 AM Paul E. McKenney, <paulmck at kernel.org> wrote:
>
> > On Thu, Oct 31, 2019 at 06:31:28AM +0700, Phong Tran wrote:
> > > Sync the format with current state of kernel documentation.
> > > This change base on rcu-dev branch
> > > what changed:
> > > - Format bullet lists
> > > - Add literal blocks
> > >
> > > Signed-off-by: Phong Tran <tranmanphong at gmail.com>
> >
> > Queued and pushed with updated subject line and commit log, thank you!
> >
> > Could you and Madhuparna please review and test each other's
> > .rst-conversion patches?
> >
>
> Sure, I will do it.
Thank you, Madhuparna!
Thanx, Paul
> Regards
> Madhuparna
>
>
> > Thanx, Paul
> >
> > > ---
> > > Documentation/RCU/index.rst | 1 +
> > > .../RCU/{whatisRCU.txt => whatisRCU.rst} | 150 +++++++++++-------
> > > 2 files changed, 90 insertions(+), 61 deletions(-)
> > > rename Documentation/RCU/{whatisRCU.txt => whatisRCU.rst} (91%)
> > >
> > > diff --git a/Documentation/RCU/index.rst b/Documentation/RCU/index.rst
> > > index 627128c230dc..b9b11481c727 100644
> > > --- a/Documentation/RCU/index.rst
> > > +++ b/Documentation/RCU/index.rst
> > > @@ -8,6 +8,7 @@ RCU concepts
> > > :maxdepth: 3
> > >
> > > arrayRCU
> > > + whatisRCU
> > > rcu
> > > listRCU
> > > NMI-RCU
> > > diff --git a/Documentation/RCU/whatisRCU.txt
> > b/Documentation/RCU/whatisRCU.rst
> > > similarity index 91%
> > > rename from Documentation/RCU/whatisRCU.txt
> > > rename to Documentation/RCU/whatisRCU.rst
> > > index 58ba05c4d97f..70d0e4c21917 100644
> > > --- a/Documentation/RCU/whatisRCU.txt
> > > +++ b/Documentation/RCU/whatisRCU.rst
> > > @@ -1,15 +1,18 @@
> > > +.. _rcu_doc:
> > > +
> > > What is RCU? -- "Read, Copy, Update"
> > > +======================================
> > >
> > > Please note that the "What is RCU?" LWN series is an excellent place
> > > to start learning about RCU:
> > >
> > > -1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> > > -2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> > > -3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> > > -4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> > > - 2010 Big API Table http://lwn.net/Articles/419086/
> > > -5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> > > - 2014 Big API Table http://lwn.net/Articles/609973/
> > > +| 1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> > > +| 2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> > > +| 3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> > > +| 4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> > > +| 2010 Big API Table http://lwn.net/Articles/419086/
> > > +| 5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> > > +| 2014 Big API Table http://lwn.net/Articles/609973/
> > >
> > >
> > > What is RCU?
> > > @@ -51,6 +54,7 @@ never need this document anyway. ;-)
> > >
> > >
> > > 1. RCU OVERVIEW
> > > +----------------
> > >
> > > The basic idea behind RCU is to split updates into "removal" and
> > > "reclamation" phases. The removal phase removes references to data
> > items
> > > @@ -118,6 +122,7 @@ Read on to learn about how RCU's API makes this easy.
> > >
> > >
> > > 2. WHAT IS RCU'S CORE API?
> > > +---------------------------
> > >
> > > The core RCU API is quite small:
> > >
> > > @@ -166,7 +171,7 @@ synchronize_rcu()
> > > read-side critical sections on all CPUs have completed.
> > > Note that synchronize_rcu() will -not- necessarily wait for
> > > any subsequent RCU read-side critical sections to complete.
> > > - For example, consider the following sequence of events:
> > > + For example, consider the following sequence of events::
> > >
> > > CPU 0 CPU 1 CPU 2
> > > ----------------- ------------------------- ---------------
> > > @@ -248,13 +253,13 @@ rcu_dereference()
> > >
> > > Common coding practice uses rcu_dereference() to copy an
> > > RCU-protected pointer to a local variable, then dereferences
> > > - this local variable, for example as follows:
> > > + this local variable, for example as follows::
> > >
> > > p = rcu_dereference(head.next);
> > > return p->data;
> > >
> > > However, in this case, one could just as easily combine these
> > > - into one statement:
> > > + into one statement::
> > >
> > > return rcu_dereference(head.next)->data;
> > >
> > > @@ -267,7 +272,7 @@ rcu_dereference()
> > >
> > > Note that the value returned by rcu_dereference() is valid
> > > only within the enclosing RCU read-side critical section [1].
> > > - For example, the following is -not- legal:
> > > + For example, the following is -not- legal::
> > >
> > > rcu_read_lock();
> > > p = rcu_dereference(head.next);
> > > @@ -315,6 +320,7 @@ rcu_dereference()
> > >
> > > The following diagram shows how each API communicates among the
> > > reader, updater, and reclaimer.
> > > +::
> > >
> > >
> > > rcu_assign_pointer()
> > > @@ -377,10 +383,12 @@ for specialized uses, but are relatively uncommon.
> > >
> > >
> > > 3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
> > > +-----------------------------------------------
> > >
> > > This section shows a simple use of the core RCU API to protect a
> > > global pointer to a dynamically allocated structure. More-typical
> > > uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt.
> > > +::
> > >
> > > struct foo {
> > > int a;
> > > @@ -467,13 +475,14 @@ arrayRCU.txt, and NMI-RCU.txt.
> > >
> > >
> > > 4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
> > > +--------------------------------------------
> > >
> > > In the example above, foo_update_a() blocks until a grace period
> > elapses.
> > > This is quite simple, but in some cases one cannot afford to wait so
> > > long -- there might be other high-priority work to be done.
> > >
> > > In such cases, one uses call_rcu() rather than synchronize_rcu().
> > > -The call_rcu() API is as follows:
> > > +The call_rcu() API is as follows::
> > >
> > > void call_rcu(struct rcu_head * head,
> > > void (*func)(struct rcu_head *head));
> > > @@ -481,7 +490,7 @@ The call_rcu() API is as follows:
> > > This function invokes func(head) after a grace period has elapsed.
> > > This invocation might happen from either softirq or process context,
> > > so the function is not permitted to block. The foo struct needs to
> > > -have an rcu_head structure added, perhaps as follows:
> > > +have an rcu_head structure added, perhaps as follows::
> > >
> > > struct foo {
> > > int a;
> > > @@ -490,7 +499,7 @@ have an rcu_head structure added, perhaps as follows:
> > > struct rcu_head rcu;
> > > };
> > >
> > > -The foo_update_a() function might then be written as follows:
> > > +The foo_update_a() function might then be written as follows::
> > >
> > > /*
> > > * Create a new struct foo that is the same as the one currently
> > > @@ -520,7 +529,7 @@ The foo_update_a() function might then be written as
> > follows:
> > > call_rcu(&old_fp->rcu, foo_reclaim);
> > > }
> > >
> > > -The foo_reclaim() function might appear as follows:
> > > +The foo_reclaim() function might appear as follows::
> > >
> > > void foo_reclaim(struct rcu_head *rp)
> > > {
> > > @@ -552,7 +561,7 @@ o Use call_rcu() -after- removing a data element
> > from an
> > >
> > > If the callback for call_rcu() is not doing anything more than calling
> > > kfree() on the structure, you can use kfree_rcu() instead of call_rcu()
> > > -to avoid having to write your own callback:
> > > +to avoid having to write your own callback::
> > >
> > > kfree_rcu(old_fp, rcu);
> > >
> > > @@ -560,6 +569,7 @@ Again, see checklist.txt for additional rules
> > governing the use of RCU.
> > >
> > >
> > > 5. WHAT ARE SOME SIMPLE IMPLEMENTATIONS OF RCU?
> > > +------------------------------------------------
> > >
> > > One of the nice things about RCU is that it has extremely simple "toy"
> > > implementations that are a good first step towards understanding the
> > > @@ -591,7 +601,7 @@ you allow nested rcu_read_lock() calls, you can
> > deadlock.
> > > However, it is probably the easiest implementation to relate to, so is
> > > a good starting point.
> > >
> > > -It is extremely simple:
> > > +It is extremely simple::
> > >
> > > static DEFINE_RWLOCK(rcu_gp_mutex);
> > >
> > > @@ -614,7 +624,7 @@ It is extremely simple:
> > >
> > > [You can ignore rcu_assign_pointer() and rcu_dereference() without
> > missing
> > > much. But here are simplified versions anyway. And whatever you do,
> > > -don't forget about them when submitting patches making use of RCU!]
> > > +don't forget about them when submitting patches making use of RCU!]::
> > >
> > > #define rcu_assign_pointer(p, v) \
> > > ({ \
> > > @@ -659,6 +669,7 @@ This section presents a "toy" RCU implementation
> > that is based on
> > > on features such as hotplug CPU and the ability to run in CONFIG_PREEMPT
> > > kernels. The definitions of rcu_dereference() and rcu_assign_pointer()
> > > are the same as those shown in the preceding section, so they are
> > omitted.
> > > +::
> > >
> > > void rcu_read_lock(void) { }
> > >
> > > @@ -707,10 +718,12 @@ Quick Quiz #3: If it is illegal to block in an
> > RCU read-side
> > >
> > >
> > > 6. ANALOGY WITH READER-WRITER LOCKING
> > > +--------------------------------------
> > >
> > > Although RCU can be used in many different ways, a very common use of
> > > RCU is analogous to reader-writer locking. The following unified
> > > diff shows how closely related RCU and reader-writer locking can be.
> > > +::
> > >
> > > @@ -5,5 +5,5 @@ struct el {
> > > int data;
> > > @@ -762,7 +775,7 @@ diff shows how closely related RCU and reader-writer
> > locking can be.
> > > return 0;
> > > }
> > >
> > > -Or, for those who prefer a side-by-side listing:
> > > +Or, for those who prefer a side-by-side listing::
> > >
> > > 1 struct el { 1 struct el {
> > > 2 struct list_head list; 2 struct list_head list;
> > > @@ -774,40 +787,44 @@ Or, for those who prefer a side-by-side listing:
> > > 8 rwlock_t listmutex; 8 spinlock_t listmutex;
> > > 9 struct el head; 9 struct el head;
> > >
> > > - 1 int search(long key, int *result) 1 int search(long key, int
> > *result)
> > > - 2 { 2 {
> > > - 3 struct list_head *lp; 3 struct list_head *lp;
> > > - 4 struct el *p; 4 struct el *p;
> > > - 5 5
> > > - 6 read_lock(&listmutex); 6 rcu_read_lock();
> > > - 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
> > head, lp) {
> > > - 8 if (p->key == key) { 8 if (p->key == key) {
> > > - 9 *result = p->data; 9 *result = p->data;
> > > -10 read_unlock(&listmutex); 10 rcu_read_unlock();
> > > -11 return 1; 11 return 1;
> > > -12 } 12 }
> > > -13 } 13 }
> > > -14 read_unlock(&listmutex); 14 rcu_read_unlock();
> > > -15 return 0; 15 return 0;
> > > -16 } 16 }
> > > -
> > > - 1 int delete(long key) 1 int delete(long key)
> > > - 2 { 2 {
> > > - 3 struct el *p; 3 struct el *p;
> > > - 4 4
> > > - 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> > > - 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p,
> > head, lp) {
> > > - 7 if (p->key == key) { 7 if (p->key == key) {
> > > - 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> > > - 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
> > > - 10 synchronize_rcu();
> > > -10 kfree(p); 11 kfree(p);
> > > -11 return 1; 12 return 1;
> > > -12 } 13 }
> > > -13 } 14 }
> > > -14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> > > -15 return 0; 16 return 0;
> > > -16 } 17 }
> > > +::
> > > +
> > > + 1 int search(long key, int *result) 1 int search(long key, int
> > *result)
> > > + 2 { 2 {
> > > + 3 struct list_head *lp; 3 struct list_head *lp;
> > > + 4 struct el *p; 4 struct el *p;
> > > + 5 5
> > > + 6 read_lock(&listmutex); 6 rcu_read_lock();
> > > + 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
> > head, lp) {
> > > + 8 if (p->key == key) { 8 if (p->key == key) {
> > > + 9 *result = p->data; 9 *result = p->data;
> > > + 10 read_unlock(&listmutex); 10 rcu_read_unlock();
> > > + 11 return 1; 11 return 1;
> > > + 12 } 12 }
> > > + 13 } 13 }
> > > + 14 read_unlock(&listmutex); 14 rcu_read_unlock();
> > > + 15 return 0; 15 return 0;
> > > + 16 } 16 }
> > > +
> > > +::
> > > +
> > > + 1 int delete(long key) 1 int delete(long key)
> > > + 2 { 2 {
> > > + 3 struct el *p; 3 struct el *p;
> > > + 4 4
> > > + 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> > > + 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p,
> > head, lp) {
> > > + 7 if (p->key == key) { 7 if (p->key == key) {
> > > + 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> > > + 9 write_unlock(&listmutex); 9
> > spin_unlock(&listmutex);
> > > + 10 synchronize_rcu();
> > > + 10 kfree(p); 11 kfree(p);
> > > + 11 return 1; 12 return 1;
> > > + 12 } 13 }
> > > + 13 } 14 }
> > > + 14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> > > + 15 return 0; 16 return 0;
> > > + 16 } 17 }
> > >
> > > Either way, the differences are quite small. Read-side locking moves
> > > to rcu_read_lock() and rcu_read_unlock, update-side locking moves from
> > > @@ -827,13 +844,14 @@ be used in place of synchronize_rcu().
> > >
> > >
> > > 7. FULL LIST OF RCU APIs
> > > +-------------------------
> > >
> > > The RCU APIs are documented in docbook-format header comments in the
> > > Linux-kernel source code, but it helps to have a full list of the
> > > APIs, since there does not appear to be a way to categorize them
> > > in docbook. Here is the list, by category.
> > >
> > > -RCU list traversal:
> > > +RCU list traversal::
> > >
> > > list_entry_rcu
> > > list_first_entry_rcu
> > > @@ -854,7 +872,7 @@ RCU list traversal:
> > > hlist_bl_first_rcu
> > > hlist_bl_for_each_entry_rcu
> > >
> > > -RCU pointer/list update:
> > > +RCU pointer/list udate::
> > >
> > > rcu_assign_pointer
> > > list_add_rcu
> > > @@ -876,7 +894,9 @@ RCU pointer/list update:
> > > hlist_bl_del_rcu
> > > hlist_bl_set_first_rcu
> > >
> > > -RCU: Critical sections Grace period Barrier
> > > +RCU::
> > > +
> > > + Critical sections Grace period Barrier
> > >
> > > rcu_read_lock synchronize_net rcu_barrier
> > > rcu_read_unlock synchronize_rcu
> > > @@ -885,7 +905,9 @@ RCU: Critical sections Grace period
> > Barrier
> > > rcu_dereference_check kfree_rcu
> > > rcu_dereference_protected
> > >
> > > -bh: Critical sections Grace period Barrier
> > > +bh::
> > > +
> > > + Critical sections Grace period Barrier
> > >
> > > rcu_read_lock_bh call_rcu rcu_barrier
> > > rcu_read_unlock_bh synchronize_rcu
> > > @@ -896,7 +918,9 @@ bh: Critical sections Grace period
> > Barrier
> > > rcu_dereference_bh_protected
> > > rcu_read_lock_bh_held
> > >
> > > -sched: Critical sections Grace period Barrier
> > > +sched::
> > > +
> > > + Critical sections Grace period Barrier
> > >
> > > rcu_read_lock_sched call_rcu rcu_barrier
> > > rcu_read_unlock_sched synchronize_rcu
> > > @@ -910,7 +934,9 @@ sched: Critical sections Grace period
> > Barrier
> > > rcu_read_lock_sched_held
> > >
> > >
> > > -SRCU: Critical sections Grace period Barrier
> > > +SRCU::
> > > +
> > > + Critical sections Grace period Barrier
> > >
> > > srcu_read_lock call_srcu srcu_barrier
> > > srcu_read_unlock synchronize_srcu
> > > @@ -918,13 +944,14 @@ SRCU: Critical sections Grace period
> > Barrier
> > > srcu_dereference_check
> > > srcu_read_lock_held
> > >
> > > -SRCU: Initialization/cleanup
> > > +SRCU: Initialization/cleanup::
> > > +
> > > DEFINE_SRCU
> > > DEFINE_STATIC_SRCU
> > > init_srcu_struct
> > > cleanup_srcu_struct
> > >
> > > -All: lockdep-checked RCU-protected pointer access
> > > +All: lockdep-checked RCU-protected pointer access::
> > >
> > > rcu_access_pointer
> > > rcu_dereference_raw
> > > @@ -976,6 +1003,7 @@ the right tool for your job.
> > >
> > >
> > > 8. ANSWERS TO QUICK QUIZZES
> > > +----------------------------
> > >
> > > Quick Quiz #1: Why is this argument naive? How could a deadlock
> > > occur when using this algorithm in a real-world Linux
> > > --
> > > 2.20.1
> > >
> >
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-11-01 7:53 ` paulmck
@ 2019-11-01 7:53 ` Paul E. McKenney
2019-11-01 7:53 ` Paul E. McKenney
1 sibling, 0 replies; 23+ messages in thread
From: Paul E. McKenney @ 2019-11-01 7:53 UTC (permalink / raw)
On Fri, Nov 01, 2019 at 09:03:57AM +0530, Madhuparna Bhowmik wrote:
> On Fri, 1 Nov, 2019, 4:24 AM Paul E. McKenney, <paulmck at kernel.org> wrote:
>
> > On Thu, Oct 31, 2019 at 06:31:28AM +0700, Phong Tran wrote:
> > > Sync the format with current state of kernel documentation.
> > > This change base on rcu-dev branch
> > > what changed:
> > > - Format bullet lists
> > > - Add literal blocks
> > >
> > > Signed-off-by: Phong Tran <tranmanphong at gmail.com>
> >
> > Queued and pushed with updated subject line and commit log, thank you!
> >
> > Could you and Madhuparna please review and test each other's
> > .rst-conversion patches?
> >
>
> Sure, I will do it.
Thank you, Madhuparna!
Thanx, Paul
> Regards
> Madhuparna
>
>
> > Thanx, Paul
> >
> > > ---
> > > Documentation/RCU/index.rst | 1 +
> > > .../RCU/{whatisRCU.txt => whatisRCU.rst} | 150 +++++++++++-------
> > > 2 files changed, 90 insertions(+), 61 deletions(-)
> > > rename Documentation/RCU/{whatisRCU.txt => whatisRCU.rst} (91%)
> > >
> > > diff --git a/Documentation/RCU/index.rst b/Documentation/RCU/index.rst
> > > index 627128c230dc..b9b11481c727 100644
> > > --- a/Documentation/RCU/index.rst
> > > +++ b/Documentation/RCU/index.rst
> > > @@ -8,6 +8,7 @@ RCU concepts
> > > :maxdepth: 3
> > >
> > > arrayRCU
> > > + whatisRCU
> > > rcu
> > > listRCU
> > > NMI-RCU
> > > diff --git a/Documentation/RCU/whatisRCU.txt
> > b/Documentation/RCU/whatisRCU.rst
> > > similarity index 91%
> > > rename from Documentation/RCU/whatisRCU.txt
> > > rename to Documentation/RCU/whatisRCU.rst
> > > index 58ba05c4d97f..70d0e4c21917 100644
> > > --- a/Documentation/RCU/whatisRCU.txt
> > > +++ b/Documentation/RCU/whatisRCU.rst
> > > @@ -1,15 +1,18 @@
> > > +.. _rcu_doc:
> > > +
> > > What is RCU? -- "Read, Copy, Update"
> > > +======================================
> > >
> > > Please note that the "What is RCU?" LWN series is an excellent place
> > > to start learning about RCU:
> > >
> > > -1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> > > -2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> > > -3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> > > -4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> > > - 2010 Big API Table http://lwn.net/Articles/419086/
> > > -5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> > > - 2014 Big API Table http://lwn.net/Articles/609973/
> > > +| 1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> > > +| 2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> > > +| 3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> > > +| 4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> > > +| 2010 Big API Table http://lwn.net/Articles/419086/
> > > +| 5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> > > +| 2014 Big API Table http://lwn.net/Articles/609973/
> > >
> > >
> > > What is RCU?
> > > @@ -51,6 +54,7 @@ never need this document anyway. ;-)
> > >
> > >
> > > 1. RCU OVERVIEW
> > > +----------------
> > >
> > > The basic idea behind RCU is to split updates into "removal" and
> > > "reclamation" phases. The removal phase removes references to data
> > items
> > > @@ -118,6 +122,7 @@ Read on to learn about how RCU's API makes this easy.
> > >
> > >
> > > 2. WHAT IS RCU'S CORE API?
> > > +---------------------------
> > >
> > > The core RCU API is quite small:
> > >
> > > @@ -166,7 +171,7 @@ synchronize_rcu()
> > > read-side critical sections on all CPUs have completed.
> > > Note that synchronize_rcu() will -not- necessarily wait for
> > > any subsequent RCU read-side critical sections to complete.
> > > - For example, consider the following sequence of events:
> > > + For example, consider the following sequence of events::
> > >
> > > CPU 0 CPU 1 CPU 2
> > > ----------------- ------------------------- ---------------
> > > @@ -248,13 +253,13 @@ rcu_dereference()
> > >
> > > Common coding practice uses rcu_dereference() to copy an
> > > RCU-protected pointer to a local variable, then dereferences
> > > - this local variable, for example as follows:
> > > + this local variable, for example as follows::
> > >
> > > p = rcu_dereference(head.next);
> > > return p->data;
> > >
> > > However, in this case, one could just as easily combine these
> > > - into one statement:
> > > + into one statement::
> > >
> > > return rcu_dereference(head.next)->data;
> > >
> > > @@ -267,7 +272,7 @@ rcu_dereference()
> > >
> > > Note that the value returned by rcu_dereference() is valid
> > > only within the enclosing RCU read-side critical section [1].
> > > - For example, the following is -not- legal:
> > > + For example, the following is -not- legal::
> > >
> > > rcu_read_lock();
> > > p = rcu_dereference(head.next);
> > > @@ -315,6 +320,7 @@ rcu_dereference()
> > >
> > > The following diagram shows how each API communicates among the
> > > reader, updater, and reclaimer.
> > > +::
> > >
> > >
> > > rcu_assign_pointer()
> > > @@ -377,10 +383,12 @@ for specialized uses, but are relatively uncommon.
> > >
> > >
> > > 3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
> > > +-----------------------------------------------
> > >
> > > This section shows a simple use of the core RCU API to protect a
> > > global pointer to a dynamically allocated structure. More-typical
> > > uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt.
> > > +::
> > >
> > > struct foo {
> > > int a;
> > > @@ -467,13 +475,14 @@ arrayRCU.txt, and NMI-RCU.txt.
> > >
> > >
> > > 4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
> > > +--------------------------------------------
> > >
> > > In the example above, foo_update_a() blocks until a grace period
> > elapses.
> > > This is quite simple, but in some cases one cannot afford to wait so
> > > long -- there might be other high-priority work to be done.
> > >
> > > In such cases, one uses call_rcu() rather than synchronize_rcu().
> > > -The call_rcu() API is as follows:
> > > +The call_rcu() API is as follows::
> > >
> > > void call_rcu(struct rcu_head * head,
> > > void (*func)(struct rcu_head *head));
> > > @@ -481,7 +490,7 @@ The call_rcu() API is as follows:
> > > This function invokes func(head) after a grace period has elapsed.
> > > This invocation might happen from either softirq or process context,
> > > so the function is not permitted to block. The foo struct needs to
> > > -have an rcu_head structure added, perhaps as follows:
> > > +have an rcu_head structure added, perhaps as follows::
> > >
> > > struct foo {
> > > int a;
> > > @@ -490,7 +499,7 @@ have an rcu_head structure added, perhaps as follows:
> > > struct rcu_head rcu;
> > > };
> > >
> > > -The foo_update_a() function might then be written as follows:
> > > +The foo_update_a() function might then be written as follows::
> > >
> > > /*
> > > * Create a new struct foo that is the same as the one currently
> > > @@ -520,7 +529,7 @@ The foo_update_a() function might then be written as
> > follows:
> > > call_rcu(&old_fp->rcu, foo_reclaim);
> > > }
> > >
> > > -The foo_reclaim() function might appear as follows:
> > > +The foo_reclaim() function might appear as follows::
> > >
> > > void foo_reclaim(struct rcu_head *rp)
> > > {
> > > @@ -552,7 +561,7 @@ o Use call_rcu() -after- removing a data element
> > from an
> > >
> > > If the callback for call_rcu() is not doing anything more than calling
> > > kfree() on the structure, you can use kfree_rcu() instead of call_rcu()
> > > -to avoid having to write your own callback:
> > > +to avoid having to write your own callback::
> > >
> > > kfree_rcu(old_fp, rcu);
> > >
> > > @@ -560,6 +569,7 @@ Again, see checklist.txt for additional rules
> > governing the use of RCU.
> > >
> > >
> > > 5. WHAT ARE SOME SIMPLE IMPLEMENTATIONS OF RCU?
> > > +------------------------------------------------
> > >
> > > One of the nice things about RCU is that it has extremely simple "toy"
> > > implementations that are a good first step towards understanding the
> > > @@ -591,7 +601,7 @@ you allow nested rcu_read_lock() calls, you can
> > deadlock.
> > > However, it is probably the easiest implementation to relate to, so is
> > > a good starting point.
> > >
> > > -It is extremely simple:
> > > +It is extremely simple::
> > >
> > > static DEFINE_RWLOCK(rcu_gp_mutex);
> > >
> > > @@ -614,7 +624,7 @@ It is extremely simple:
> > >
> > > [You can ignore rcu_assign_pointer() and rcu_dereference() without
> > missing
> > > much. But here are simplified versions anyway. And whatever you do,
> > > -don't forget about them when submitting patches making use of RCU!]
> > > +don't forget about them when submitting patches making use of RCU!]::
> > >
> > > #define rcu_assign_pointer(p, v) \
> > > ({ \
> > > @@ -659,6 +669,7 @@ This section presents a "toy" RCU implementation
> > that is based on
> > > on features such as hotplug CPU and the ability to run in CONFIG_PREEMPT
> > > kernels. The definitions of rcu_dereference() and rcu_assign_pointer()
> > > are the same as those shown in the preceding section, so they are
> > omitted.
> > > +::
> > >
> > > void rcu_read_lock(void) { }
> > >
> > > @@ -707,10 +718,12 @@ Quick Quiz #3: If it is illegal to block in an
> > RCU read-side
> > >
> > >
> > > 6. ANALOGY WITH READER-WRITER LOCKING
> > > +--------------------------------------
> > >
> > > Although RCU can be used in many different ways, a very common use of
> > > RCU is analogous to reader-writer locking. The following unified
> > > diff shows how closely related RCU and reader-writer locking can be.
> > > +::
> > >
> > > @@ -5,5 +5,5 @@ struct el {
> > > int data;
> > > @@ -762,7 +775,7 @@ diff shows how closely related RCU and reader-writer
> > locking can be.
> > > return 0;
> > > }
> > >
> > > -Or, for those who prefer a side-by-side listing:
> > > +Or, for those who prefer a side-by-side listing::
> > >
> > > 1 struct el { 1 struct el {
> > > 2 struct list_head list; 2 struct list_head list;
> > > @@ -774,40 +787,44 @@ Or, for those who prefer a side-by-side listing:
> > > 8 rwlock_t listmutex; 8 spinlock_t listmutex;
> > > 9 struct el head; 9 struct el head;
> > >
> > > - 1 int search(long key, int *result) 1 int search(long key, int
> > *result)
> > > - 2 { 2 {
> > > - 3 struct list_head *lp; 3 struct list_head *lp;
> > > - 4 struct el *p; 4 struct el *p;
> > > - 5 5
> > > - 6 read_lock(&listmutex); 6 rcu_read_lock();
> > > - 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
> > head, lp) {
> > > - 8 if (p->key == key) { 8 if (p->key == key) {
> > > - 9 *result = p->data; 9 *result = p->data;
> > > -10 read_unlock(&listmutex); 10 rcu_read_unlock();
> > > -11 return 1; 11 return 1;
> > > -12 } 12 }
> > > -13 } 13 }
> > > -14 read_unlock(&listmutex); 14 rcu_read_unlock();
> > > -15 return 0; 15 return 0;
> > > -16 } 16 }
> > > -
> > > - 1 int delete(long key) 1 int delete(long key)
> > > - 2 { 2 {
> > > - 3 struct el *p; 3 struct el *p;
> > > - 4 4
> > > - 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> > > - 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p,
> > head, lp) {
> > > - 7 if (p->key == key) { 7 if (p->key == key) {
> > > - 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> > > - 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
> > > - 10 synchronize_rcu();
> > > -10 kfree(p); 11 kfree(p);
> > > -11 return 1; 12 return 1;
> > > -12 } 13 }
> > > -13 } 14 }
> > > -14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> > > -15 return 0; 16 return 0;
> > > -16 } 17 }
> > > +::
> > > +
> > > + 1 int search(long key, int *result) 1 int search(long key, int
> > *result)
> > > + 2 { 2 {
> > > + 3 struct list_head *lp; 3 struct list_head *lp;
> > > + 4 struct el *p; 4 struct el *p;
> > > + 5 5
> > > + 6 read_lock(&listmutex); 6 rcu_read_lock();
> > > + 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
> > head, lp) {
> > > + 8 if (p->key == key) { 8 if (p->key == key) {
> > > + 9 *result = p->data; 9 *result = p->data;
> > > + 10 read_unlock(&listmutex); 10 rcu_read_unlock();
> > > + 11 return 1; 11 return 1;
> > > + 12 } 12 }
> > > + 13 } 13 }
> > > + 14 read_unlock(&listmutex); 14 rcu_read_unlock();
> > > + 15 return 0; 15 return 0;
> > > + 16 } 16 }
> > > +
> > > +::
> > > +
> > > + 1 int delete(long key) 1 int delete(long key)
> > > + 2 { 2 {
> > > + 3 struct el *p; 3 struct el *p;
> > > + 4 4
> > > + 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> > > + 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p,
> > head, lp) {
> > > + 7 if (p->key == key) { 7 if (p->key == key) {
> > > + 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> > > + 9 write_unlock(&listmutex); 9
> > spin_unlock(&listmutex);
> > > + 10 synchronize_rcu();
> > > + 10 kfree(p); 11 kfree(p);
> > > + 11 return 1; 12 return 1;
> > > + 12 } 13 }
> > > + 13 } 14 }
> > > + 14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> > > + 15 return 0; 16 return 0;
> > > + 16 } 17 }
> > >
> > > Either way, the differences are quite small. Read-side locking moves
> > > to rcu_read_lock() and rcu_read_unlock, update-side locking moves from
> > > @@ -827,13 +844,14 @@ be used in place of synchronize_rcu().
> > >
> > >
> > > 7. FULL LIST OF RCU APIs
> > > +-------------------------
> > >
> > > The RCU APIs are documented in docbook-format header comments in the
> > > Linux-kernel source code, but it helps to have a full list of the
> > > APIs, since there does not appear to be a way to categorize them
> > > in docbook. Here is the list, by category.
> > >
> > > -RCU list traversal:
> > > +RCU list traversal::
> > >
> > > list_entry_rcu
> > > list_first_entry_rcu
> > > @@ -854,7 +872,7 @@ RCU list traversal:
> > > hlist_bl_first_rcu
> > > hlist_bl_for_each_entry_rcu
> > >
> > > -RCU pointer/list update:
> > > +RCU pointer/list udate::
> > >
> > > rcu_assign_pointer
> > > list_add_rcu
> > > @@ -876,7 +894,9 @@ RCU pointer/list update:
> > > hlist_bl_del_rcu
> > > hlist_bl_set_first_rcu
> > >
> > > -RCU: Critical sections Grace period Barrier
> > > +RCU::
> > > +
> > > + Critical sections Grace period Barrier
> > >
> > > rcu_read_lock synchronize_net rcu_barrier
> > > rcu_read_unlock synchronize_rcu
> > > @@ -885,7 +905,9 @@ RCU: Critical sections Grace period
> > Barrier
> > > rcu_dereference_check kfree_rcu
> > > rcu_dereference_protected
> > >
> > > -bh: Critical sections Grace period Barrier
> > > +bh::
> > > +
> > > + Critical sections Grace period Barrier
> > >
> > > rcu_read_lock_bh call_rcu rcu_barrier
> > > rcu_read_unlock_bh synchronize_rcu
> > > @@ -896,7 +918,9 @@ bh: Critical sections Grace period
> > Barrier
> > > rcu_dereference_bh_protected
> > > rcu_read_lock_bh_held
> > >
> > > -sched: Critical sections Grace period Barrier
> > > +sched::
> > > +
> > > + Critical sections Grace period Barrier
> > >
> > > rcu_read_lock_sched call_rcu rcu_barrier
> > > rcu_read_unlock_sched synchronize_rcu
> > > @@ -910,7 +934,9 @@ sched: Critical sections Grace period
> > Barrier
> > > rcu_read_lock_sched_held
> > >
> > >
> > > -SRCU: Critical sections Grace period Barrier
> > > +SRCU::
> > > +
> > > + Critical sections Grace period Barrier
> > >
> > > srcu_read_lock call_srcu srcu_barrier
> > > srcu_read_unlock synchronize_srcu
> > > @@ -918,13 +944,14 @@ SRCU: Critical sections Grace period
> > Barrier
> > > srcu_dereference_check
> > > srcu_read_lock_held
> > >
> > > -SRCU: Initialization/cleanup
> > > +SRCU: Initialization/cleanup::
> > > +
> > > DEFINE_SRCU
> > > DEFINE_STATIC_SRCU
> > > init_srcu_struct
> > > cleanup_srcu_struct
> > >
> > > -All: lockdep-checked RCU-protected pointer access
> > > +All: lockdep-checked RCU-protected pointer access::
> > >
> > > rcu_access_pointer
> > > rcu_dereference_raw
> > > @@ -976,6 +1003,7 @@ the right tool for your job.
> > >
> > >
> > > 8. ANSWERS TO QUICK QUIZZES
> > > +----------------------------
> > >
> > > Quick Quiz #1: Why is this argument naive? How could a deadlock
> > > occur when using this algorithm in a real-world Linux
> > > --
> > > 2.20.1
> > >
> >
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-11-01 7:53 ` paulmck
2019-11-01 7:53 ` Paul E. McKenney
@ 2019-11-01 7:53 ` Paul E. McKenney
1 sibling, 0 replies; 23+ messages in thread
From: Paul E. McKenney @ 2019-11-01 7:53 UTC (permalink / raw)
To: Madhuparna Bhowmik
Cc: corbet, linux-doc, jiangshanlai, josh, rostedt, linux-kernel,
rcu, mathieu.desnoyers, joel, linux-kernel-mentees
On Fri, Nov 01, 2019 at 09:03:57AM +0530, Madhuparna Bhowmik wrote:
> On Fri, 1 Nov, 2019, 4:24 AM Paul E. McKenney, <paulmck@kernel.org> wrote:
>
> > On Thu, Oct 31, 2019 at 06:31:28AM +0700, Phong Tran wrote:
> > > Sync the format with current state of kernel documentation.
> > > This change base on rcu-dev branch
> > > what changed:
> > > - Format bullet lists
> > > - Add literal blocks
> > >
> > > Signed-off-by: Phong Tran <tranmanphong@gmail.com>
> >
> > Queued and pushed with updated subject line and commit log, thank you!
> >
> > Could you and Madhuparna please review and test each other's
> > .rst-conversion patches?
> >
>
> Sure, I will do it.
Thank you, Madhuparna!
Thanx, Paul
> Regards
> Madhuparna
>
>
> > Thanx, Paul
> >
> > > ---
> > > Documentation/RCU/index.rst | 1 +
> > > .../RCU/{whatisRCU.txt => whatisRCU.rst} | 150 +++++++++++-------
> > > 2 files changed, 90 insertions(+), 61 deletions(-)
> > > rename Documentation/RCU/{whatisRCU.txt => whatisRCU.rst} (91%)
> > >
> > > diff --git a/Documentation/RCU/index.rst b/Documentation/RCU/index.rst
> > > index 627128c230dc..b9b11481c727 100644
> > > --- a/Documentation/RCU/index.rst
> > > +++ b/Documentation/RCU/index.rst
> > > @@ -8,6 +8,7 @@ RCU concepts
> > > :maxdepth: 3
> > >
> > > arrayRCU
> > > + whatisRCU
> > > rcu
> > > listRCU
> > > NMI-RCU
> > > diff --git a/Documentation/RCU/whatisRCU.txt
> > b/Documentation/RCU/whatisRCU.rst
> > > similarity index 91%
> > > rename from Documentation/RCU/whatisRCU.txt
> > > rename to Documentation/RCU/whatisRCU.rst
> > > index 58ba05c4d97f..70d0e4c21917 100644
> > > --- a/Documentation/RCU/whatisRCU.txt
> > > +++ b/Documentation/RCU/whatisRCU.rst
> > > @@ -1,15 +1,18 @@
> > > +.. _rcu_doc:
> > > +
> > > What is RCU? -- "Read, Copy, Update"
> > > +======================================
> > >
> > > Please note that the "What is RCU?" LWN series is an excellent place
> > > to start learning about RCU:
> > >
> > > -1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> > > -2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> > > -3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> > > -4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> > > - 2010 Big API Table http://lwn.net/Articles/419086/
> > > -5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> > > - 2014 Big API Table http://lwn.net/Articles/609973/
> > > +| 1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> > > +| 2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> > > +| 3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> > > +| 4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> > > +| 2010 Big API Table http://lwn.net/Articles/419086/
> > > +| 5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> > > +| 2014 Big API Table http://lwn.net/Articles/609973/
> > >
> > >
> > > What is RCU?
> > > @@ -51,6 +54,7 @@ never need this document anyway. ;-)
> > >
> > >
> > > 1. RCU OVERVIEW
> > > +----------------
> > >
> > > The basic idea behind RCU is to split updates into "removal" and
> > > "reclamation" phases. The removal phase removes references to data
> > items
> > > @@ -118,6 +122,7 @@ Read on to learn about how RCU's API makes this easy.
> > >
> > >
> > > 2. WHAT IS RCU'S CORE API?
> > > +---------------------------
> > >
> > > The core RCU API is quite small:
> > >
> > > @@ -166,7 +171,7 @@ synchronize_rcu()
> > > read-side critical sections on all CPUs have completed.
> > > Note that synchronize_rcu() will -not- necessarily wait for
> > > any subsequent RCU read-side critical sections to complete.
> > > - For example, consider the following sequence of events:
> > > + For example, consider the following sequence of events::
> > >
> > > CPU 0 CPU 1 CPU 2
> > > ----------------- ------------------------- ---------------
> > > @@ -248,13 +253,13 @@ rcu_dereference()
> > >
> > > Common coding practice uses rcu_dereference() to copy an
> > > RCU-protected pointer to a local variable, then dereferences
> > > - this local variable, for example as follows:
> > > + this local variable, for example as follows::
> > >
> > > p = rcu_dereference(head.next);
> > > return p->data;
> > >
> > > However, in this case, one could just as easily combine these
> > > - into one statement:
> > > + into one statement::
> > >
> > > return rcu_dereference(head.next)->data;
> > >
> > > @@ -267,7 +272,7 @@ rcu_dereference()
> > >
> > > Note that the value returned by rcu_dereference() is valid
> > > only within the enclosing RCU read-side critical section [1].
> > > - For example, the following is -not- legal:
> > > + For example, the following is -not- legal::
> > >
> > > rcu_read_lock();
> > > p = rcu_dereference(head.next);
> > > @@ -315,6 +320,7 @@ rcu_dereference()
> > >
> > > The following diagram shows how each API communicates among the
> > > reader, updater, and reclaimer.
> > > +::
> > >
> > >
> > > rcu_assign_pointer()
> > > @@ -377,10 +383,12 @@ for specialized uses, but are relatively uncommon.
> > >
> > >
> > > 3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
> > > +-----------------------------------------------
> > >
> > > This section shows a simple use of the core RCU API to protect a
> > > global pointer to a dynamically allocated structure. More-typical
> > > uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt.
> > > +::
> > >
> > > struct foo {
> > > int a;
> > > @@ -467,13 +475,14 @@ arrayRCU.txt, and NMI-RCU.txt.
> > >
> > >
> > > 4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
> > > +--------------------------------------------
> > >
> > > In the example above, foo_update_a() blocks until a grace period
> > elapses.
> > > This is quite simple, but in some cases one cannot afford to wait so
> > > long -- there might be other high-priority work to be done.
> > >
> > > In such cases, one uses call_rcu() rather than synchronize_rcu().
> > > -The call_rcu() API is as follows:
> > > +The call_rcu() API is as follows::
> > >
> > > void call_rcu(struct rcu_head * head,
> > > void (*func)(struct rcu_head *head));
> > > @@ -481,7 +490,7 @@ The call_rcu() API is as follows:
> > > This function invokes func(head) after a grace period has elapsed.
> > > This invocation might happen from either softirq or process context,
> > > so the function is not permitted to block. The foo struct needs to
> > > -have an rcu_head structure added, perhaps as follows:
> > > +have an rcu_head structure added, perhaps as follows::
> > >
> > > struct foo {
> > > int a;
> > > @@ -490,7 +499,7 @@ have an rcu_head structure added, perhaps as follows:
> > > struct rcu_head rcu;
> > > };
> > >
> > > -The foo_update_a() function might then be written as follows:
> > > +The foo_update_a() function might then be written as follows::
> > >
> > > /*
> > > * Create a new struct foo that is the same as the one currently
> > > @@ -520,7 +529,7 @@ The foo_update_a() function might then be written as
> > follows:
> > > call_rcu(&old_fp->rcu, foo_reclaim);
> > > }
> > >
> > > -The foo_reclaim() function might appear as follows:
> > > +The foo_reclaim() function might appear as follows::
> > >
> > > void foo_reclaim(struct rcu_head *rp)
> > > {
> > > @@ -552,7 +561,7 @@ o Use call_rcu() -after- removing a data element
> > from an
> > >
> > > If the callback for call_rcu() is not doing anything more than calling
> > > kfree() on the structure, you can use kfree_rcu() instead of call_rcu()
> > > -to avoid having to write your own callback:
> > > +to avoid having to write your own callback::
> > >
> > > kfree_rcu(old_fp, rcu);
> > >
> > > @@ -560,6 +569,7 @@ Again, see checklist.txt for additional rules
> > governing the use of RCU.
> > >
> > >
> > > 5. WHAT ARE SOME SIMPLE IMPLEMENTATIONS OF RCU?
> > > +------------------------------------------------
> > >
> > > One of the nice things about RCU is that it has extremely simple "toy"
> > > implementations that are a good first step towards understanding the
> > > @@ -591,7 +601,7 @@ you allow nested rcu_read_lock() calls, you can
> > deadlock.
> > > However, it is probably the easiest implementation to relate to, so is
> > > a good starting point.
> > >
> > > -It is extremely simple:
> > > +It is extremely simple::
> > >
> > > static DEFINE_RWLOCK(rcu_gp_mutex);
> > >
> > > @@ -614,7 +624,7 @@ It is extremely simple:
> > >
> > > [You can ignore rcu_assign_pointer() and rcu_dereference() without
> > missing
> > > much. But here are simplified versions anyway. And whatever you do,
> > > -don't forget about them when submitting patches making use of RCU!]
> > > +don't forget about them when submitting patches making use of RCU!]::
> > >
> > > #define rcu_assign_pointer(p, v) \
> > > ({ \
> > > @@ -659,6 +669,7 @@ This section presents a "toy" RCU implementation
> > that is based on
> > > on features such as hotplug CPU and the ability to run in CONFIG_PREEMPT
> > > kernels. The definitions of rcu_dereference() and rcu_assign_pointer()
> > > are the same as those shown in the preceding section, so they are
> > omitted.
> > > +::
> > >
> > > void rcu_read_lock(void) { }
> > >
> > > @@ -707,10 +718,12 @@ Quick Quiz #3: If it is illegal to block in an
> > RCU read-side
> > >
> > >
> > > 6. ANALOGY WITH READER-WRITER LOCKING
> > > +--------------------------------------
> > >
> > > Although RCU can be used in many different ways, a very common use of
> > > RCU is analogous to reader-writer locking. The following unified
> > > diff shows how closely related RCU and reader-writer locking can be.
> > > +::
> > >
> > > @@ -5,5 +5,5 @@ struct el {
> > > int data;
> > > @@ -762,7 +775,7 @@ diff shows how closely related RCU and reader-writer
> > locking can be.
> > > return 0;
> > > }
> > >
> > > -Or, for those who prefer a side-by-side listing:
> > > +Or, for those who prefer a side-by-side listing::
> > >
> > > 1 struct el { 1 struct el {
> > > 2 struct list_head list; 2 struct list_head list;
> > > @@ -774,40 +787,44 @@ Or, for those who prefer a side-by-side listing:
> > > 8 rwlock_t listmutex; 8 spinlock_t listmutex;
> > > 9 struct el head; 9 struct el head;
> > >
> > > - 1 int search(long key, int *result) 1 int search(long key, int
> > *result)
> > > - 2 { 2 {
> > > - 3 struct list_head *lp; 3 struct list_head *lp;
> > > - 4 struct el *p; 4 struct el *p;
> > > - 5 5
> > > - 6 read_lock(&listmutex); 6 rcu_read_lock();
> > > - 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
> > head, lp) {
> > > - 8 if (p->key == key) { 8 if (p->key == key) {
> > > - 9 *result = p->data; 9 *result = p->data;
> > > -10 read_unlock(&listmutex); 10 rcu_read_unlock();
> > > -11 return 1; 11 return 1;
> > > -12 } 12 }
> > > -13 } 13 }
> > > -14 read_unlock(&listmutex); 14 rcu_read_unlock();
> > > -15 return 0; 15 return 0;
> > > -16 } 16 }
> > > -
> > > - 1 int delete(long key) 1 int delete(long key)
> > > - 2 { 2 {
> > > - 3 struct el *p; 3 struct el *p;
> > > - 4 4
> > > - 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> > > - 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p,
> > head, lp) {
> > > - 7 if (p->key == key) { 7 if (p->key == key) {
> > > - 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> > > - 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
> > > - 10 synchronize_rcu();
> > > -10 kfree(p); 11 kfree(p);
> > > -11 return 1; 12 return 1;
> > > -12 } 13 }
> > > -13 } 14 }
> > > -14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> > > -15 return 0; 16 return 0;
> > > -16 } 17 }
> > > +::
> > > +
> > > + 1 int search(long key, int *result) 1 int search(long key, int
> > *result)
> > > + 2 { 2 {
> > > + 3 struct list_head *lp; 3 struct list_head *lp;
> > > + 4 struct el *p; 4 struct el *p;
> > > + 5 5
> > > + 6 read_lock(&listmutex); 6 rcu_read_lock();
> > > + 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
> > head, lp) {
> > > + 8 if (p->key == key) { 8 if (p->key == key) {
> > > + 9 *result = p->data; 9 *result = p->data;
> > > + 10 read_unlock(&listmutex); 10 rcu_read_unlock();
> > > + 11 return 1; 11 return 1;
> > > + 12 } 12 }
> > > + 13 } 13 }
> > > + 14 read_unlock(&listmutex); 14 rcu_read_unlock();
> > > + 15 return 0; 15 return 0;
> > > + 16 } 16 }
> > > +
> > > +::
> > > +
> > > + 1 int delete(long key) 1 int delete(long key)
> > > + 2 { 2 {
> > > + 3 struct el *p; 3 struct el *p;
> > > + 4 4
> > > + 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> > > + 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p,
> > head, lp) {
> > > + 7 if (p->key == key) { 7 if (p->key == key) {
> > > + 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> > > + 9 write_unlock(&listmutex); 9
> > spin_unlock(&listmutex);
> > > + 10 synchronize_rcu();
> > > + 10 kfree(p); 11 kfree(p);
> > > + 11 return 1; 12 return 1;
> > > + 12 } 13 }
> > > + 13 } 14 }
> > > + 14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> > > + 15 return 0; 16 return 0;
> > > + 16 } 17 }
> > >
> > > Either way, the differences are quite small. Read-side locking moves
> > > to rcu_read_lock() and rcu_read_unlock, update-side locking moves from
> > > @@ -827,13 +844,14 @@ be used in place of synchronize_rcu().
> > >
> > >
> > > 7. FULL LIST OF RCU APIs
> > > +-------------------------
> > >
> > > The RCU APIs are documented in docbook-format header comments in the
> > > Linux-kernel source code, but it helps to have a full list of the
> > > APIs, since there does not appear to be a way to categorize them
> > > in docbook. Here is the list, by category.
> > >
> > > -RCU list traversal:
> > > +RCU list traversal::
> > >
> > > list_entry_rcu
> > > list_first_entry_rcu
> > > @@ -854,7 +872,7 @@ RCU list traversal:
> > > hlist_bl_first_rcu
> > > hlist_bl_for_each_entry_rcu
> > >
> > > -RCU pointer/list update:
> > > +RCU pointer/list udate::
> > >
> > > rcu_assign_pointer
> > > list_add_rcu
> > > @@ -876,7 +894,9 @@ RCU pointer/list update:
> > > hlist_bl_del_rcu
> > > hlist_bl_set_first_rcu
> > >
> > > -RCU: Critical sections Grace period Barrier
> > > +RCU::
> > > +
> > > + Critical sections Grace period Barrier
> > >
> > > rcu_read_lock synchronize_net rcu_barrier
> > > rcu_read_unlock synchronize_rcu
> > > @@ -885,7 +905,9 @@ RCU: Critical sections Grace period
> > Barrier
> > > rcu_dereference_check kfree_rcu
> > > rcu_dereference_protected
> > >
> > > -bh: Critical sections Grace period Barrier
> > > +bh::
> > > +
> > > + Critical sections Grace period Barrier
> > >
> > > rcu_read_lock_bh call_rcu rcu_barrier
> > > rcu_read_unlock_bh synchronize_rcu
> > > @@ -896,7 +918,9 @@ bh: Critical sections Grace period
> > Barrier
> > > rcu_dereference_bh_protected
> > > rcu_read_lock_bh_held
> > >
> > > -sched: Critical sections Grace period Barrier
> > > +sched::
> > > +
> > > + Critical sections Grace period Barrier
> > >
> > > rcu_read_lock_sched call_rcu rcu_barrier
> > > rcu_read_unlock_sched synchronize_rcu
> > > @@ -910,7 +934,9 @@ sched: Critical sections Grace period
> > Barrier
> > > rcu_read_lock_sched_held
> > >
> > >
> > > -SRCU: Critical sections Grace period Barrier
> > > +SRCU::
> > > +
> > > + Critical sections Grace period Barrier
> > >
> > > srcu_read_lock call_srcu srcu_barrier
> > > srcu_read_unlock synchronize_srcu
> > > @@ -918,13 +944,14 @@ SRCU: Critical sections Grace period
> > Barrier
> > > srcu_dereference_check
> > > srcu_read_lock_held
> > >
> > > -SRCU: Initialization/cleanup
> > > +SRCU: Initialization/cleanup::
> > > +
> > > DEFINE_SRCU
> > > DEFINE_STATIC_SRCU
> > > init_srcu_struct
> > > cleanup_srcu_struct
> > >
> > > -All: lockdep-checked RCU-protected pointer access
> > > +All: lockdep-checked RCU-protected pointer access::
> > >
> > > rcu_access_pointer
> > > rcu_dereference_raw
> > > @@ -976,6 +1003,7 @@ the right tool for your job.
> > >
> > >
> > > 8. ANSWERS TO QUICK QUIZZES
> > > +----------------------------
> > >
> > > Quick Quiz #1: Why is this argument naive? How could a deadlock
> > > occur when using this algorithm in a real-world Linux
> > > --
> > > 2.20.1
> > >
> >
_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees
^ permalink raw reply [flat|nested] 23+ messages in thread
* [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-10-30 23:31 [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst tranmanphong
2019-10-30 23:31 ` Phong Tran
2019-10-31 22:54 ` paulmck
@ 2019-11-02 8:31 ` madhuparnabhowmik04
2019-11-02 8:31 ` Madhuparna Bhowmik
` (2 more replies)
2 siblings, 3 replies; 23+ messages in thread
From: madhuparnabhowmik04 @ 2019-11-02 8:31 UTC (permalink / raw)
I reviewed this patch, and I have the following suggestions:
On Thu, Oct 31, 2019 at 5:04 AM Phong Tran <tranmanphong at gmail.com> wrote:
> Sync the format with current state of kernel documentation.
> This change base on rcu-dev branch
> what changed:
> - Format bullet lists
> - Add literal blocks
>
> Signed-off-by: Phong Tran <tranmanphong at gmail.com>
> ---
> Documentation/RCU/index.rst | 1 +
> .../RCU/{whatisRCU.txt => whatisRCU.rst} | 150 +++++++++++-------
> 2 files changed, 90 insertions(+), 61 deletions(-)
> rename Documentation/RCU/{whatisRCU.txt => whatisRCU.rst} (91%)
>
> diff --git a/Documentation/RCU/index.rst b/Documentation/RCU/index.rst
> index 627128c230dc..b9b11481c727 100644
> --- a/Documentation/RCU/index.rst
> +++ b/Documentation/RCU/index.rst
> @@ -8,6 +8,7 @@ RCU concepts
> :maxdepth: 3
>
> arrayRCU
> + whatisRCU
> rcu
> listRCU
> NMI-RCU
> diff --git a/Documentation/RCU/whatisRCU.txt
> b/Documentation/RCU/whatisRCU.rst
> similarity index 91%
> rename from Documentation/RCU/whatisRCU.txt
> rename to Documentation/RCU/whatisRCU.rst
> index 58ba05c4d97f..70d0e4c21917 100644
> --- a/Documentation/RCU/whatisRCU.txt
> +++ b/Documentation/RCU/whatisRCU.rst
> @@ -1,15 +1,18 @@
> +.. _rcu_doc:
> +
> What is RCU? -- "Read, Copy, Update"
> +======================================
>
> Please note that the "What is RCU?" LWN series is an excellent place
> to start learning about RCU:
>
> -1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> -2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> -3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> -4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> - 2010 Big API Table http://lwn.net/Articles/419086/
> -5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> - 2014 Big API Table http://lwn.net/Articles/609973/
> +| 1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> +| 2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> +| 3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> +| 4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> +| 2010 Big API Table http://lwn.net/Articles/419086/
> +| 5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> +| 2014 Big API Table http://lwn.net/Articles/609973/
>
>
Adding an external link here would be better.
like this : `text <link URL>`_
What is RCU?
> @@ -51,6 +54,7 @@ never need this document anyway. ;-)
>
>
>
There is a list of topics that are covered in this documentation.
Like this:
1. RCU OVERVIEW
2. WHAT IS RCU?S CORE API?
3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
...
since this document is quite big adding cross-references to the above
would be helpful.
> 1. RCU OVERVIEW
> +----------------
>
> The basic idea behind RCU is to split updates into "removal" and
> "reclamation" phases. The removal phase removes references to data items
> @@ -118,6 +122,7 @@ Read on to learn about how RCU's API makes this easy.
>
>
> 2. WHAT IS RCU'S CORE API?
> +---------------------------
>
> The core RCU API is quite small:
>
> @@ -166,7 +171,7 @@ synchronize_rcu()
> read-side critical sections on all CPUs have completed.
> Note that synchronize_rcu() will -not- necessarily wait for
> any subsequent RCU read-side critical sections to complete.
> - For example, consider the following sequence of events:
> + For example, consider the following sequence of events::
>
> CPU 0 CPU 1 CPU 2
> ----------------- ------------------------- ---------------
> @@ -248,13 +253,13 @@ rcu_dereference()
>
> Common coding practice uses rcu_dereference() to copy an
> RCU-protected pointer to a local variable, then dereferences
> - this local variable, for example as follows:
> + this local variable, for example as follows::
>
> p = rcu_dereference(head.next);
> return p->data;
>
> However, in this case, one could just as easily combine these
> - into one statement:
> + into one statement::
>
> return rcu_dereference(head.next)->data;
>
> @@ -267,7 +272,7 @@ rcu_dereference()
>
> Note that the value returned by rcu_dereference() is valid
> only within the enclosing RCU read-side critical section [1].
> - For example, the following is -not- legal:
> + For example, the following is -not- legal::
>
> rcu_read_lock();
> p = rcu_dereference(head.next);
> @@ -315,6 +320,7 @@ rcu_dereference()
>
> The following diagram shows how each API communicates among the
> reader, updater, and reclaimer.
> +::
>
>
> rcu_assign_pointer()
> @@ -377,10 +383,12 @@ for specialized uses, but are relatively uncommon.
>
>
> 3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
> +-----------------------------------------------
>
> This section shows a simple use of the core RCU API to protect a
> global pointer to a dynamically allocated structure. More-typical
> uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt.
> +::
>
> struct foo {
> int a;
> @@ -467,13 +475,14 @@ arrayRCU.txt, and NMI-RCU.txt.
>
>
> 4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
> +--------------------------------------------
>
> In the example above, foo_update_a() blocks until a grace period elapses.
> This is quite simple, but in some cases one cannot afford to wait so
> long -- there might be other high-priority work to be done.
>
> In such cases, one uses call_rcu() rather than synchronize_rcu().
> -The call_rcu() API is as follows:
> +The call_rcu() API is as follows::
>
> void call_rcu(struct rcu_head * head,
> void (*func)(struct rcu_head *head));
> @@ -481,7 +490,7 @@ The call_rcu() API is as follows:
> This function invokes func(head) after a grace period has elapsed.
> This invocation might happen from either softirq or process context,
> so the function is not permitted to block. The foo struct needs to
> -have an rcu_head structure added, perhaps as follows:
> +have an rcu_head structure added, perhaps as follows::
>
> struct foo {
> int a;
> @@ -490,7 +499,7 @@ have an rcu_head structure added, perhaps as follows:
> struct rcu_head rcu;
> };
>
> -The foo_update_a() function might then be written as follows:
> +The foo_update_a() function might then be written as follows::
>
> /*
> * Create a new struct foo that is the same as the one currently
> @@ -520,7 +529,7 @@ The foo_update_a() function might then be written as
> follows:
> call_rcu(&old_fp->rcu, foo_reclaim);
> }
>
> -The foo_reclaim() function might appear as follows:
> +The foo_reclaim() function might appear as follows::
>
> void foo_reclaim(struct rcu_head *rp)
> {
> @@ -552,7 +561,7 @@ o Use call_rcu() -after- removing a data element
> from an
>
> If the callback for call_rcu() is not doing anything more than calling
> kfree() on the structure, you can use kfree_rcu() instead of call_rcu()
> -to avoid having to write your own callback:
> +to avoid having to write your own callback::
>
> kfree_rcu(old_fp, rcu);
>
> @@ -560,6 +569,7 @@ Again, see checklist.txt for additional rules
> governing the use of RCU.
>
>
> 5. WHAT ARE SOME SIMPLE IMPLEMENTATIONS OF RCU?
> +------------------------------------------------
>
> One of the nice things about RCU is that it has extremely simple "toy"
> implementations that are a good first step towards understanding the
> @@ -591,7 +601,7 @@ you allow nested rcu_read_lock() calls, you can
> deadlock.
> However, it is probably the easiest implementation to relate to, so is
> a good starting point.
>
> -It is extremely simple:
> +It is extremely simple::
>
> static DEFINE_RWLOCK(rcu_gp_mutex);
>
> @@ -614,7 +624,7 @@ It is extremely simple:
>
> [You can ignore rcu_assign_pointer() and rcu_dereference() without missing
> much. But here are simplified versions anyway. And whatever you do,
> -don't forget about them when submitting patches making use of RCU!]
> +don't forget about them when submitting patches making use of RCU!]::
>
> #define rcu_assign_pointer(p, v) \
> ({ \
> @@ -659,6 +669,7 @@ This section presents a "toy" RCU implementation that
> is based on
> on features such as hotplug CPU and the ability to run in CONFIG_PREEMPT
> kernels. The definitions of rcu_dereference() and rcu_assign_pointer()
> are the same as those shown in the preceding section, so they are omitted.
> +::
>
> void rcu_read_lock(void) { }
>
> @@ -707,10 +718,12 @@ Quick Quiz #3: If it is illegal to block in an RCU
> read-side
>
>
> 6. ANALOGY WITH READER-WRITER LOCKING
> +--------------------------------------
>
> Although RCU can be used in many different ways, a very common use of
> RCU is analogous to reader-writer locking. The following unified
> diff shows how closely related RCU and reader-writer locking can be.
> +::
>
> @@ -5,5 +5,5 @@ struct el {
> int data;
> @@ -762,7 +775,7 @@ diff shows how closely related RCU and reader-writer
> locking can be.
> return 0;
> }
>
> -Or, for those who prefer a side-by-side listing:
> +Or, for those who prefer a side-by-side listing::
>
> 1 struct el { 1 struct el {
> 2 struct list_head list; 2 struct list_head list;
> @@ -774,40 +787,44 @@ Or, for those who prefer a side-by-side listing:
> 8 rwlock_t listmutex; 8 spinlock_t listmutex;
> 9 struct el head; 9 struct el head;
>
> - 1 int search(long key, int *result) 1 int search(long key, int
> *result)
> - 2 { 2 {
> - 3 struct list_head *lp; 3 struct list_head *lp;
> - 4 struct el *p; 4 struct el *p;
> - 5 5
> - 6 read_lock(&listmutex); 6 rcu_read_lock();
> - 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
> head, lp) {
> - 8 if (p->key == key) { 8 if (p->key == key) {
> - 9 *result = p->data; 9 *result = p->data;
> -10 read_unlock(&listmutex); 10 rcu_read_unlock();
> -11 return 1; 11 return 1;
> -12 } 12 }
> -13 } 13 }
> -14 read_unlock(&listmutex); 14 rcu_read_unlock();
> -15 return 0; 15 return 0;
> -16 } 16 }
> -
> - 1 int delete(long key) 1 int delete(long key)
> - 2 { 2 {
> - 3 struct el *p; 3 struct el *p;
> - 4 4
> - 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> - 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p, head,
> lp) {
> - 7 if (p->key == key) { 7 if (p->key == key) {
> - 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> - 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
> - 10 synchronize_rcu();
> -10 kfree(p); 11 kfree(p);
> -11 return 1; 12 return 1;
> -12 } 13 }
> -13 } 14 }
> -14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> -15 return 0; 16 return 0;
> -16 } 17 }
> +::
> +
> + 1 int search(long key, int *result) 1 int search(long key, int
> *result)
> + 2 { 2 {
> + 3 struct list_head *lp; 3 struct list_head *lp;
> + 4 struct el *p; 4 struct el *p;
> + 5 5
> + 6 read_lock(&listmutex); 6 rcu_read_lock();
> + 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
> head, lp) {
> + 8 if (p->key == key) { 8 if (p->key == key) {
> + 9 *result = p->data; 9 *result = p->data;
> + 10 read_unlock(&listmutex); 10 rcu_read_unlock();
> + 11 return 1; 11 return 1;
> + 12 } 12 }
> + 13 } 13 }
> + 14 read_unlock(&listmutex); 14 rcu_read_unlock();
> + 15 return 0; 15 return 0;
> + 16 } 16 }
> +
> +::
> +
> + 1 int delete(long key) 1 int delete(long key)
> + 2 { 2 {
> + 3 struct el *p; 3 struct el *p;
> + 4 4
> + 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> + 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p, head,
> lp) {
> + 7 if (p->key == key) { 7 if (p->key == key) {
> + 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> + 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
> + 10 synchronize_rcu();
> + 10 kfree(p); 11 kfree(p);
> + 11 return 1; 12 return 1;
> + 12 } 13 }
> + 13 } 14 }
> + 14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> + 15 return 0; 16 return 0;
> + 16 } 17 }
>
> Either way, the differences are quite small. Read-side locking moves
> to rcu_read_lock() and rcu_read_unlock, update-side locking moves from
> @@ -827,13 +844,14 @@ be used in place of synchronize_rcu().
>
>
> 7. FULL LIST OF RCU APIs
> +-------------------------
>
> The RCU APIs are documented in docbook-format header comments in the
> Linux-kernel source code, but it helps to have a full list of the
> APIs, since there does not appear to be a way to categorize them
> in docbook. Here is the list, by category.
>
> -RCU list traversal:
> +RCU list traversal::
>
> list_entry_rcu
> list_first_entry_rcu
> @@ -854,7 +872,7 @@ RCU list traversal:
> hlist_bl_first_rcu
> hlist_bl_for_each_entry_rcu
>
> -RCU pointer/list update:
> +RCU pointer/list udate::
>
> rcu_assign_pointer
> list_add_rcu
> @@ -876,7 +894,9 @@ RCU pointer/list update:
> hlist_bl_del_rcu
> hlist_bl_set_first_rcu
>
> -RCU: Critical sections Grace period Barrier
> +RCU::
> +
> + Critical sections Grace period Barrier
>
> rcu_read_lock synchronize_net rcu_barrier
> rcu_read_unlock synchronize_rcu
> @@ -885,7 +905,9 @@ RCU: Critical sections Grace period
> Barrier
> rcu_dereference_check kfree_rcu
> rcu_dereference_protected
>
> -bh: Critical sections Grace period Barrier
> +bh::
> +
> + Critical sections Grace period Barrier
>
> rcu_read_lock_bh call_rcu rcu_barrier
> rcu_read_unlock_bh synchronize_rcu
> @@ -896,7 +918,9 @@ bh: Critical sections Grace period
> Barrier
> rcu_dereference_bh_protected
> rcu_read_lock_bh_held
>
> -sched: Critical sections Grace period Barrier
> +sched::
> +
> + Critical sections Grace period Barrier
>
> rcu_read_lock_sched call_rcu rcu_barrier
> rcu_read_unlock_sched synchronize_rcu
> @@ -910,7 +934,9 @@ sched: Critical sections Grace period
> Barrier
> rcu_read_lock_sched_held
>
>
> -SRCU: Critical sections Grace period Barrier
> +SRCU::
> +
> + Critical sections Grace period Barrier
>
> srcu_read_lock call_srcu srcu_barrier
> srcu_read_unlock synchronize_srcu
> @@ -918,13 +944,14 @@ SRCU: Critical sections Grace period
> Barrier
> srcu_dereference_check
> srcu_read_lock_held
>
> -SRCU: Initialization/cleanup
> +SRCU: Initialization/cleanup::
> +
> DEFINE_SRCU
> DEFINE_STATIC_SRCU
> init_srcu_struct
> cleanup_srcu_struct
>
> -All: lockdep-checked RCU-protected pointer access
> +All: lockdep-checked RCU-protected pointer access::
>
> rcu_access_pointer
> rcu_dereference_raw
> @@ -976,6 +1003,7 @@ the right tool for your job.
>
>
> 8. ANSWERS TO QUICK QUIZZES
> +----------------------------
>
> Quick Quiz #1: Why is this argument naive? How could a deadlock
> occur when using this algorithm in a real-world Linux
>
Here, the formatting is not proper. In the rst file, the question should be
added in the next line after Quick Quiz #1. Currently, half of the question
appears in bold and the rest half does not.
Also, as followed in all the documents there should be a cross-reference to
the answer to this question. As this document is quite big having
references would be helpful.
The same applies to all other quick quiz questions in this document and in
the Answers section as well the questions do not appear properly, half in
bold text and half not bold.
Apart from this, the other added changes look good!
Thank you
Madhuparna
--
> 2.20.1
>
> _______________________________________________
> Linux-kernel-mentees mailing list
> Linux-kernel-mentees at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees
>
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^ permalink raw reply [flat|nested] 23+ messages in thread
* [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-11-02 8:31 ` madhuparnabhowmik04
@ 2019-11-02 8:31 ` Madhuparna Bhowmik
2019-11-02 8:31 ` Madhuparna Bhowmik
2019-11-02 12:00 ` tranmanphong
2 siblings, 0 replies; 23+ messages in thread
From: Madhuparna Bhowmik @ 2019-11-02 8:31 UTC (permalink / raw)
I reviewed this patch, and I have the following suggestions:
On Thu, Oct 31, 2019 at 5:04 AM Phong Tran <tranmanphong at gmail.com> wrote:
> Sync the format with current state of kernel documentation.
> This change base on rcu-dev branch
> what changed:
> - Format bullet lists
> - Add literal blocks
>
> Signed-off-by: Phong Tran <tranmanphong at gmail.com>
> ---
> Documentation/RCU/index.rst | 1 +
> .../RCU/{whatisRCU.txt => whatisRCU.rst} | 150 +++++++++++-------
> 2 files changed, 90 insertions(+), 61 deletions(-)
> rename Documentation/RCU/{whatisRCU.txt => whatisRCU.rst} (91%)
>
> diff --git a/Documentation/RCU/index.rst b/Documentation/RCU/index.rst
> index 627128c230dc..b9b11481c727 100644
> --- a/Documentation/RCU/index.rst
> +++ b/Documentation/RCU/index.rst
> @@ -8,6 +8,7 @@ RCU concepts
> :maxdepth: 3
>
> arrayRCU
> + whatisRCU
> rcu
> listRCU
> NMI-RCU
> diff --git a/Documentation/RCU/whatisRCU.txt
> b/Documentation/RCU/whatisRCU.rst
> similarity index 91%
> rename from Documentation/RCU/whatisRCU.txt
> rename to Documentation/RCU/whatisRCU.rst
> index 58ba05c4d97f..70d0e4c21917 100644
> --- a/Documentation/RCU/whatisRCU.txt
> +++ b/Documentation/RCU/whatisRCU.rst
> @@ -1,15 +1,18 @@
> +.. _rcu_doc:
> +
> What is RCU? -- "Read, Copy, Update"
> +======================================
>
> Please note that the "What is RCU?" LWN series is an excellent place
> to start learning about RCU:
>
> -1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> -2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> -3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> -4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> - 2010 Big API Table http://lwn.net/Articles/419086/
> -5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> - 2014 Big API Table http://lwn.net/Articles/609973/
> +| 1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> +| 2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> +| 3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> +| 4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> +| 2010 Big API Table http://lwn.net/Articles/419086/
> +| 5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> +| 2014 Big API Table http://lwn.net/Articles/609973/
>
>
Adding an external link here would be better.
like this : `text <link URL>`_
What is RCU?
> @@ -51,6 +54,7 @@ never need this document anyway. ;-)
>
>
>
There is a list of topics that are covered in this documentation.
Like this:
1. RCU OVERVIEW
2. WHAT IS RCU?S CORE API?
3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
...
since this document is quite big adding cross-references to the above
would be helpful.
> 1. RCU OVERVIEW
> +----------------
>
> The basic idea behind RCU is to split updates into "removal" and
> "reclamation" phases. The removal phase removes references to data items
> @@ -118,6 +122,7 @@ Read on to learn about how RCU's API makes this easy.
>
>
> 2. WHAT IS RCU'S CORE API?
> +---------------------------
>
> The core RCU API is quite small:
>
> @@ -166,7 +171,7 @@ synchronize_rcu()
> read-side critical sections on all CPUs have completed.
> Note that synchronize_rcu() will -not- necessarily wait for
> any subsequent RCU read-side critical sections to complete.
> - For example, consider the following sequence of events:
> + For example, consider the following sequence of events::
>
> CPU 0 CPU 1 CPU 2
> ----------------- ------------------------- ---------------
> @@ -248,13 +253,13 @@ rcu_dereference()
>
> Common coding practice uses rcu_dereference() to copy an
> RCU-protected pointer to a local variable, then dereferences
> - this local variable, for example as follows:
> + this local variable, for example as follows::
>
> p = rcu_dereference(head.next);
> return p->data;
>
> However, in this case, one could just as easily combine these
> - into one statement:
> + into one statement::
>
> return rcu_dereference(head.next)->data;
>
> @@ -267,7 +272,7 @@ rcu_dereference()
>
> Note that the value returned by rcu_dereference() is valid
> only within the enclosing RCU read-side critical section [1].
> - For example, the following is -not- legal:
> + For example, the following is -not- legal::
>
> rcu_read_lock();
> p = rcu_dereference(head.next);
> @@ -315,6 +320,7 @@ rcu_dereference()
>
> The following diagram shows how each API communicates among the
> reader, updater, and reclaimer.
> +::
>
>
> rcu_assign_pointer()
> @@ -377,10 +383,12 @@ for specialized uses, but are relatively uncommon.
>
>
> 3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
> +-----------------------------------------------
>
> This section shows a simple use of the core RCU API to protect a
> global pointer to a dynamically allocated structure. More-typical
> uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt.
> +::
>
> struct foo {
> int a;
> @@ -467,13 +475,14 @@ arrayRCU.txt, and NMI-RCU.txt.
>
>
> 4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
> +--------------------------------------------
>
> In the example above, foo_update_a() blocks until a grace period elapses.
> This is quite simple, but in some cases one cannot afford to wait so
> long -- there might be other high-priority work to be done.
>
> In such cases, one uses call_rcu() rather than synchronize_rcu().
> -The call_rcu() API is as follows:
> +The call_rcu() API is as follows::
>
> void call_rcu(struct rcu_head * head,
> void (*func)(struct rcu_head *head));
> @@ -481,7 +490,7 @@ The call_rcu() API is as follows:
> This function invokes func(head) after a grace period has elapsed.
> This invocation might happen from either softirq or process context,
> so the function is not permitted to block. The foo struct needs to
> -have an rcu_head structure added, perhaps as follows:
> +have an rcu_head structure added, perhaps as follows::
>
> struct foo {
> int a;
> @@ -490,7 +499,7 @@ have an rcu_head structure added, perhaps as follows:
> struct rcu_head rcu;
> };
>
> -The foo_update_a() function might then be written as follows:
> +The foo_update_a() function might then be written as follows::
>
> /*
> * Create a new struct foo that is the same as the one currently
> @@ -520,7 +529,7 @@ The foo_update_a() function might then be written as
> follows:
> call_rcu(&old_fp->rcu, foo_reclaim);
> }
>
> -The foo_reclaim() function might appear as follows:
> +The foo_reclaim() function might appear as follows::
>
> void foo_reclaim(struct rcu_head *rp)
> {
> @@ -552,7 +561,7 @@ o Use call_rcu() -after- removing a data element
> from an
>
> If the callback for call_rcu() is not doing anything more than calling
> kfree() on the structure, you can use kfree_rcu() instead of call_rcu()
> -to avoid having to write your own callback:
> +to avoid having to write your own callback::
>
> kfree_rcu(old_fp, rcu);
>
> @@ -560,6 +569,7 @@ Again, see checklist.txt for additional rules
> governing the use of RCU.
>
>
> 5. WHAT ARE SOME SIMPLE IMPLEMENTATIONS OF RCU?
> +------------------------------------------------
>
> One of the nice things about RCU is that it has extremely simple "toy"
> implementations that are a good first step towards understanding the
> @@ -591,7 +601,7 @@ you allow nested rcu_read_lock() calls, you can
> deadlock.
> However, it is probably the easiest implementation to relate to, so is
> a good starting point.
>
> -It is extremely simple:
> +It is extremely simple::
>
> static DEFINE_RWLOCK(rcu_gp_mutex);
>
> @@ -614,7 +624,7 @@ It is extremely simple:
>
> [You can ignore rcu_assign_pointer() and rcu_dereference() without missing
> much. But here are simplified versions anyway. And whatever you do,
> -don't forget about them when submitting patches making use of RCU!]
> +don't forget about them when submitting patches making use of RCU!]::
>
> #define rcu_assign_pointer(p, v) \
> ({ \
> @@ -659,6 +669,7 @@ This section presents a "toy" RCU implementation that
> is based on
> on features such as hotplug CPU and the ability to run in CONFIG_PREEMPT
> kernels. The definitions of rcu_dereference() and rcu_assign_pointer()
> are the same as those shown in the preceding section, so they are omitted.
> +::
>
> void rcu_read_lock(void) { }
>
> @@ -707,10 +718,12 @@ Quick Quiz #3: If it is illegal to block in an RCU
> read-side
>
>
> 6. ANALOGY WITH READER-WRITER LOCKING
> +--------------------------------------
>
> Although RCU can be used in many different ways, a very common use of
> RCU is analogous to reader-writer locking. The following unified
> diff shows how closely related RCU and reader-writer locking can be.
> +::
>
> @@ -5,5 +5,5 @@ struct el {
> int data;
> @@ -762,7 +775,7 @@ diff shows how closely related RCU and reader-writer
> locking can be.
> return 0;
> }
>
> -Or, for those who prefer a side-by-side listing:
> +Or, for those who prefer a side-by-side listing::
>
> 1 struct el { 1 struct el {
> 2 struct list_head list; 2 struct list_head list;
> @@ -774,40 +787,44 @@ Or, for those who prefer a side-by-side listing:
> 8 rwlock_t listmutex; 8 spinlock_t listmutex;
> 9 struct el head; 9 struct el head;
>
> - 1 int search(long key, int *result) 1 int search(long key, int
> *result)
> - 2 { 2 {
> - 3 struct list_head *lp; 3 struct list_head *lp;
> - 4 struct el *p; 4 struct el *p;
> - 5 5
> - 6 read_lock(&listmutex); 6 rcu_read_lock();
> - 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
> head, lp) {
> - 8 if (p->key == key) { 8 if (p->key == key) {
> - 9 *result = p->data; 9 *result = p->data;
> -10 read_unlock(&listmutex); 10 rcu_read_unlock();
> -11 return 1; 11 return 1;
> -12 } 12 }
> -13 } 13 }
> -14 read_unlock(&listmutex); 14 rcu_read_unlock();
> -15 return 0; 15 return 0;
> -16 } 16 }
> -
> - 1 int delete(long key) 1 int delete(long key)
> - 2 { 2 {
> - 3 struct el *p; 3 struct el *p;
> - 4 4
> - 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> - 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p, head,
> lp) {
> - 7 if (p->key == key) { 7 if (p->key == key) {
> - 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> - 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
> - 10 synchronize_rcu();
> -10 kfree(p); 11 kfree(p);
> -11 return 1; 12 return 1;
> -12 } 13 }
> -13 } 14 }
> -14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> -15 return 0; 16 return 0;
> -16 } 17 }
> +::
> +
> + 1 int search(long key, int *result) 1 int search(long key, int
> *result)
> + 2 { 2 {
> + 3 struct list_head *lp; 3 struct list_head *lp;
> + 4 struct el *p; 4 struct el *p;
> + 5 5
> + 6 read_lock(&listmutex); 6 rcu_read_lock();
> + 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
> head, lp) {
> + 8 if (p->key == key) { 8 if (p->key == key) {
> + 9 *result = p->data; 9 *result = p->data;
> + 10 read_unlock(&listmutex); 10 rcu_read_unlock();
> + 11 return 1; 11 return 1;
> + 12 } 12 }
> + 13 } 13 }
> + 14 read_unlock(&listmutex); 14 rcu_read_unlock();
> + 15 return 0; 15 return 0;
> + 16 } 16 }
> +
> +::
> +
> + 1 int delete(long key) 1 int delete(long key)
> + 2 { 2 {
> + 3 struct el *p; 3 struct el *p;
> + 4 4
> + 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> + 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p, head,
> lp) {
> + 7 if (p->key == key) { 7 if (p->key == key) {
> + 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> + 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
> + 10 synchronize_rcu();
> + 10 kfree(p); 11 kfree(p);
> + 11 return 1; 12 return 1;
> + 12 } 13 }
> + 13 } 14 }
> + 14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> + 15 return 0; 16 return 0;
> + 16 } 17 }
>
> Either way, the differences are quite small. Read-side locking moves
> to rcu_read_lock() and rcu_read_unlock, update-side locking moves from
> @@ -827,13 +844,14 @@ be used in place of synchronize_rcu().
>
>
> 7. FULL LIST OF RCU APIs
> +-------------------------
>
> The RCU APIs are documented in docbook-format header comments in the
> Linux-kernel source code, but it helps to have a full list of the
> APIs, since there does not appear to be a way to categorize them
> in docbook. Here is the list, by category.
>
> -RCU list traversal:
> +RCU list traversal::
>
> list_entry_rcu
> list_first_entry_rcu
> @@ -854,7 +872,7 @@ RCU list traversal:
> hlist_bl_first_rcu
> hlist_bl_for_each_entry_rcu
>
> -RCU pointer/list update:
> +RCU pointer/list udate::
>
> rcu_assign_pointer
> list_add_rcu
> @@ -876,7 +894,9 @@ RCU pointer/list update:
> hlist_bl_del_rcu
> hlist_bl_set_first_rcu
>
> -RCU: Critical sections Grace period Barrier
> +RCU::
> +
> + Critical sections Grace period Barrier
>
> rcu_read_lock synchronize_net rcu_barrier
> rcu_read_unlock synchronize_rcu
> @@ -885,7 +905,9 @@ RCU: Critical sections Grace period
> Barrier
> rcu_dereference_check kfree_rcu
> rcu_dereference_protected
>
> -bh: Critical sections Grace period Barrier
> +bh::
> +
> + Critical sections Grace period Barrier
>
> rcu_read_lock_bh call_rcu rcu_barrier
> rcu_read_unlock_bh synchronize_rcu
> @@ -896,7 +918,9 @@ bh: Critical sections Grace period
> Barrier
> rcu_dereference_bh_protected
> rcu_read_lock_bh_held
>
> -sched: Critical sections Grace period Barrier
> +sched::
> +
> + Critical sections Grace period Barrier
>
> rcu_read_lock_sched call_rcu rcu_barrier
> rcu_read_unlock_sched synchronize_rcu
> @@ -910,7 +934,9 @@ sched: Critical sections Grace period
> Barrier
> rcu_read_lock_sched_held
>
>
> -SRCU: Critical sections Grace period Barrier
> +SRCU::
> +
> + Critical sections Grace period Barrier
>
> srcu_read_lock call_srcu srcu_barrier
> srcu_read_unlock synchronize_srcu
> @@ -918,13 +944,14 @@ SRCU: Critical sections Grace period
> Barrier
> srcu_dereference_check
> srcu_read_lock_held
>
> -SRCU: Initialization/cleanup
> +SRCU: Initialization/cleanup::
> +
> DEFINE_SRCU
> DEFINE_STATIC_SRCU
> init_srcu_struct
> cleanup_srcu_struct
>
> -All: lockdep-checked RCU-protected pointer access
> +All: lockdep-checked RCU-protected pointer access::
>
> rcu_access_pointer
> rcu_dereference_raw
> @@ -976,6 +1003,7 @@ the right tool for your job.
>
>
> 8. ANSWERS TO QUICK QUIZZES
> +----------------------------
>
> Quick Quiz #1: Why is this argument naive? How could a deadlock
> occur when using this algorithm in a real-world Linux
>
Here, the formatting is not proper. In the rst file, the question should be
added in the next line after Quick Quiz #1. Currently, half of the question
appears in bold and the rest half does not.
Also, as followed in all the documents there should be a cross-reference to
the answer to this question. As this document is quite big having
references would be helpful.
The same applies to all other quick quiz questions in this document and in
the Answers section as well the questions do not appear properly, half in
bold text and half not bold.
Apart from this, the other added changes look good!
Thank you
Madhuparna
--
> 2.20.1
>
> _______________________________________________
> Linux-kernel-mentees mailing list
> Linux-kernel-mentees at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees
>
?
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^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-11-02 8:31 ` madhuparnabhowmik04
2019-11-02 8:31 ` Madhuparna Bhowmik
@ 2019-11-02 8:31 ` Madhuparna Bhowmik
2019-11-02 12:00 ` tranmanphong
2 siblings, 0 replies; 23+ messages in thread
From: Madhuparna Bhowmik @ 2019-11-02 8:31 UTC (permalink / raw)
To: Phong Tran
Cc: paulmck, corbet, linux-doc, jiangshanlai, josh, rostedt,
linux-kernel, rcu, mathieu.desnoyers, Joel Fernandes,
linux-kernel-mentees
[-- Attachment #1.1: Type: text/plain, Size: 18741 bytes --]
I reviewed this patch, and I have the following suggestions:
On Thu, Oct 31, 2019 at 5:04 AM Phong Tran <tranmanphong@gmail.com> wrote:
> Sync the format with current state of kernel documentation.
> This change base on rcu-dev branch
> what changed:
> - Format bullet lists
> - Add literal blocks
>
> Signed-off-by: Phong Tran <tranmanphong@gmail.com>
> ---
> Documentation/RCU/index.rst | 1 +
> .../RCU/{whatisRCU.txt => whatisRCU.rst} | 150 +++++++++++-------
> 2 files changed, 90 insertions(+), 61 deletions(-)
> rename Documentation/RCU/{whatisRCU.txt => whatisRCU.rst} (91%)
>
> diff --git a/Documentation/RCU/index.rst b/Documentation/RCU/index.rst
> index 627128c230dc..b9b11481c727 100644
> --- a/Documentation/RCU/index.rst
> +++ b/Documentation/RCU/index.rst
> @@ -8,6 +8,7 @@ RCU concepts
> :maxdepth: 3
>
> arrayRCU
> + whatisRCU
> rcu
> listRCU
> NMI-RCU
> diff --git a/Documentation/RCU/whatisRCU.txt
> b/Documentation/RCU/whatisRCU.rst
> similarity index 91%
> rename from Documentation/RCU/whatisRCU.txt
> rename to Documentation/RCU/whatisRCU.rst
> index 58ba05c4d97f..70d0e4c21917 100644
> --- a/Documentation/RCU/whatisRCU.txt
> +++ b/Documentation/RCU/whatisRCU.rst
> @@ -1,15 +1,18 @@
> +.. _rcu_doc:
> +
> What is RCU? -- "Read, Copy, Update"
> +======================================
>
> Please note that the "What is RCU?" LWN series is an excellent place
> to start learning about RCU:
>
> -1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> -2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> -3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> -4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> - 2010 Big API Table http://lwn.net/Articles/419086/
> -5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> - 2014 Big API Table http://lwn.net/Articles/609973/
> +| 1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
> +| 2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
> +| 3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
> +| 4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
> +| 2010 Big API Table http://lwn.net/Articles/419086/
> +| 5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
> +| 2014 Big API Table http://lwn.net/Articles/609973/
>
>
Adding an external link here would be better.
like this : `text <link URL>`_
What is RCU?
> @@ -51,6 +54,7 @@ never need this document anyway. ;-)
>
>
>
There is a list of topics that are covered in this documentation.
Like this:
1. RCU OVERVIEW
2. WHAT IS RCU’S CORE API?
3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
...
since this document is quite big adding cross-references to the above
would be helpful.
> 1. RCU OVERVIEW
> +----------------
>
> The basic idea behind RCU is to split updates into "removal" and
> "reclamation" phases. The removal phase removes references to data items
> @@ -118,6 +122,7 @@ Read on to learn about how RCU's API makes this easy.
>
>
> 2. WHAT IS RCU'S CORE API?
> +---------------------------
>
> The core RCU API is quite small:
>
> @@ -166,7 +171,7 @@ synchronize_rcu()
> read-side critical sections on all CPUs have completed.
> Note that synchronize_rcu() will -not- necessarily wait for
> any subsequent RCU read-side critical sections to complete.
> - For example, consider the following sequence of events:
> + For example, consider the following sequence of events::
>
> CPU 0 CPU 1 CPU 2
> ----------------- ------------------------- ---------------
> @@ -248,13 +253,13 @@ rcu_dereference()
>
> Common coding practice uses rcu_dereference() to copy an
> RCU-protected pointer to a local variable, then dereferences
> - this local variable, for example as follows:
> + this local variable, for example as follows::
>
> p = rcu_dereference(head.next);
> return p->data;
>
> However, in this case, one could just as easily combine these
> - into one statement:
> + into one statement::
>
> return rcu_dereference(head.next)->data;
>
> @@ -267,7 +272,7 @@ rcu_dereference()
>
> Note that the value returned by rcu_dereference() is valid
> only within the enclosing RCU read-side critical section [1].
> - For example, the following is -not- legal:
> + For example, the following is -not- legal::
>
> rcu_read_lock();
> p = rcu_dereference(head.next);
> @@ -315,6 +320,7 @@ rcu_dereference()
>
> The following diagram shows how each API communicates among the
> reader, updater, and reclaimer.
> +::
>
>
> rcu_assign_pointer()
> @@ -377,10 +383,12 @@ for specialized uses, but are relatively uncommon.
>
>
> 3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
> +-----------------------------------------------
>
> This section shows a simple use of the core RCU API to protect a
> global pointer to a dynamically allocated structure. More-typical
> uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt.
> +::
>
> struct foo {
> int a;
> @@ -467,13 +475,14 @@ arrayRCU.txt, and NMI-RCU.txt.
>
>
> 4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
> +--------------------------------------------
>
> In the example above, foo_update_a() blocks until a grace period elapses.
> This is quite simple, but in some cases one cannot afford to wait so
> long -- there might be other high-priority work to be done.
>
> In such cases, one uses call_rcu() rather than synchronize_rcu().
> -The call_rcu() API is as follows:
> +The call_rcu() API is as follows::
>
> void call_rcu(struct rcu_head * head,
> void (*func)(struct rcu_head *head));
> @@ -481,7 +490,7 @@ The call_rcu() API is as follows:
> This function invokes func(head) after a grace period has elapsed.
> This invocation might happen from either softirq or process context,
> so the function is not permitted to block. The foo struct needs to
> -have an rcu_head structure added, perhaps as follows:
> +have an rcu_head structure added, perhaps as follows::
>
> struct foo {
> int a;
> @@ -490,7 +499,7 @@ have an rcu_head structure added, perhaps as follows:
> struct rcu_head rcu;
> };
>
> -The foo_update_a() function might then be written as follows:
> +The foo_update_a() function might then be written as follows::
>
> /*
> * Create a new struct foo that is the same as the one currently
> @@ -520,7 +529,7 @@ The foo_update_a() function might then be written as
> follows:
> call_rcu(&old_fp->rcu, foo_reclaim);
> }
>
> -The foo_reclaim() function might appear as follows:
> +The foo_reclaim() function might appear as follows::
>
> void foo_reclaim(struct rcu_head *rp)
> {
> @@ -552,7 +561,7 @@ o Use call_rcu() -after- removing a data element
> from an
>
> If the callback for call_rcu() is not doing anything more than calling
> kfree() on the structure, you can use kfree_rcu() instead of call_rcu()
> -to avoid having to write your own callback:
> +to avoid having to write your own callback::
>
> kfree_rcu(old_fp, rcu);
>
> @@ -560,6 +569,7 @@ Again, see checklist.txt for additional rules
> governing the use of RCU.
>
>
> 5. WHAT ARE SOME SIMPLE IMPLEMENTATIONS OF RCU?
> +------------------------------------------------
>
> One of the nice things about RCU is that it has extremely simple "toy"
> implementations that are a good first step towards understanding the
> @@ -591,7 +601,7 @@ you allow nested rcu_read_lock() calls, you can
> deadlock.
> However, it is probably the easiest implementation to relate to, so is
> a good starting point.
>
> -It is extremely simple:
> +It is extremely simple::
>
> static DEFINE_RWLOCK(rcu_gp_mutex);
>
> @@ -614,7 +624,7 @@ It is extremely simple:
>
> [You can ignore rcu_assign_pointer() and rcu_dereference() without missing
> much. But here are simplified versions anyway. And whatever you do,
> -don't forget about them when submitting patches making use of RCU!]
> +don't forget about them when submitting patches making use of RCU!]::
>
> #define rcu_assign_pointer(p, v) \
> ({ \
> @@ -659,6 +669,7 @@ This section presents a "toy" RCU implementation that
> is based on
> on features such as hotplug CPU and the ability to run in CONFIG_PREEMPT
> kernels. The definitions of rcu_dereference() and rcu_assign_pointer()
> are the same as those shown in the preceding section, so they are omitted.
> +::
>
> void rcu_read_lock(void) { }
>
> @@ -707,10 +718,12 @@ Quick Quiz #3: If it is illegal to block in an RCU
> read-side
>
>
> 6. ANALOGY WITH READER-WRITER LOCKING
> +--------------------------------------
>
> Although RCU can be used in many different ways, a very common use of
> RCU is analogous to reader-writer locking. The following unified
> diff shows how closely related RCU and reader-writer locking can be.
> +::
>
> @@ -5,5 +5,5 @@ struct el {
> int data;
> @@ -762,7 +775,7 @@ diff shows how closely related RCU and reader-writer
> locking can be.
> return 0;
> }
>
> -Or, for those who prefer a side-by-side listing:
> +Or, for those who prefer a side-by-side listing::
>
> 1 struct el { 1 struct el {
> 2 struct list_head list; 2 struct list_head list;
> @@ -774,40 +787,44 @@ Or, for those who prefer a side-by-side listing:
> 8 rwlock_t listmutex; 8 spinlock_t listmutex;
> 9 struct el head; 9 struct el head;
>
> - 1 int search(long key, int *result) 1 int search(long key, int
> *result)
> - 2 { 2 {
> - 3 struct list_head *lp; 3 struct list_head *lp;
> - 4 struct el *p; 4 struct el *p;
> - 5 5
> - 6 read_lock(&listmutex); 6 rcu_read_lock();
> - 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
> head, lp) {
> - 8 if (p->key == key) { 8 if (p->key == key) {
> - 9 *result = p->data; 9 *result = p->data;
> -10 read_unlock(&listmutex); 10 rcu_read_unlock();
> -11 return 1; 11 return 1;
> -12 } 12 }
> -13 } 13 }
> -14 read_unlock(&listmutex); 14 rcu_read_unlock();
> -15 return 0; 15 return 0;
> -16 } 16 }
> -
> - 1 int delete(long key) 1 int delete(long key)
> - 2 { 2 {
> - 3 struct el *p; 3 struct el *p;
> - 4 4
> - 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> - 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p, head,
> lp) {
> - 7 if (p->key == key) { 7 if (p->key == key) {
> - 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> - 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
> - 10 synchronize_rcu();
> -10 kfree(p); 11 kfree(p);
> -11 return 1; 12 return 1;
> -12 } 13 }
> -13 } 14 }
> -14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> -15 return 0; 16 return 0;
> -16 } 17 }
> +::
> +
> + 1 int search(long key, int *result) 1 int search(long key, int
> *result)
> + 2 { 2 {
> + 3 struct list_head *lp; 3 struct list_head *lp;
> + 4 struct el *p; 4 struct el *p;
> + 5 5
> + 6 read_lock(&listmutex); 6 rcu_read_lock();
> + 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
> head, lp) {
> + 8 if (p->key == key) { 8 if (p->key == key) {
> + 9 *result = p->data; 9 *result = p->data;
> + 10 read_unlock(&listmutex); 10 rcu_read_unlock();
> + 11 return 1; 11 return 1;
> + 12 } 12 }
> + 13 } 13 }
> + 14 read_unlock(&listmutex); 14 rcu_read_unlock();
> + 15 return 0; 15 return 0;
> + 16 } 16 }
> +
> +::
> +
> + 1 int delete(long key) 1 int delete(long key)
> + 2 { 2 {
> + 3 struct el *p; 3 struct el *p;
> + 4 4
> + 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
> + 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p, head,
> lp) {
> + 7 if (p->key == key) { 7 if (p->key == key) {
> + 8 list_del(&p->list); 8 list_del_rcu(&p->list);
> + 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
> + 10 synchronize_rcu();
> + 10 kfree(p); 11 kfree(p);
> + 11 return 1; 12 return 1;
> + 12 } 13 }
> + 13 } 14 }
> + 14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
> + 15 return 0; 16 return 0;
> + 16 } 17 }
>
> Either way, the differences are quite small. Read-side locking moves
> to rcu_read_lock() and rcu_read_unlock, update-side locking moves from
> @@ -827,13 +844,14 @@ be used in place of synchronize_rcu().
>
>
> 7. FULL LIST OF RCU APIs
> +-------------------------
>
> The RCU APIs are documented in docbook-format header comments in the
> Linux-kernel source code, but it helps to have a full list of the
> APIs, since there does not appear to be a way to categorize them
> in docbook. Here is the list, by category.
>
> -RCU list traversal:
> +RCU list traversal::
>
> list_entry_rcu
> list_first_entry_rcu
> @@ -854,7 +872,7 @@ RCU list traversal:
> hlist_bl_first_rcu
> hlist_bl_for_each_entry_rcu
>
> -RCU pointer/list update:
> +RCU pointer/list udate::
>
> rcu_assign_pointer
> list_add_rcu
> @@ -876,7 +894,9 @@ RCU pointer/list update:
> hlist_bl_del_rcu
> hlist_bl_set_first_rcu
>
> -RCU: Critical sections Grace period Barrier
> +RCU::
> +
> + Critical sections Grace period Barrier
>
> rcu_read_lock synchronize_net rcu_barrier
> rcu_read_unlock synchronize_rcu
> @@ -885,7 +905,9 @@ RCU: Critical sections Grace period
> Barrier
> rcu_dereference_check kfree_rcu
> rcu_dereference_protected
>
> -bh: Critical sections Grace period Barrier
> +bh::
> +
> + Critical sections Grace period Barrier
>
> rcu_read_lock_bh call_rcu rcu_barrier
> rcu_read_unlock_bh synchronize_rcu
> @@ -896,7 +918,9 @@ bh: Critical sections Grace period
> Barrier
> rcu_dereference_bh_protected
> rcu_read_lock_bh_held
>
> -sched: Critical sections Grace period Barrier
> +sched::
> +
> + Critical sections Grace period Barrier
>
> rcu_read_lock_sched call_rcu rcu_barrier
> rcu_read_unlock_sched synchronize_rcu
> @@ -910,7 +934,9 @@ sched: Critical sections Grace period
> Barrier
> rcu_read_lock_sched_held
>
>
> -SRCU: Critical sections Grace period Barrier
> +SRCU::
> +
> + Critical sections Grace period Barrier
>
> srcu_read_lock call_srcu srcu_barrier
> srcu_read_unlock synchronize_srcu
> @@ -918,13 +944,14 @@ SRCU: Critical sections Grace period
> Barrier
> srcu_dereference_check
> srcu_read_lock_held
>
> -SRCU: Initialization/cleanup
> +SRCU: Initialization/cleanup::
> +
> DEFINE_SRCU
> DEFINE_STATIC_SRCU
> init_srcu_struct
> cleanup_srcu_struct
>
> -All: lockdep-checked RCU-protected pointer access
> +All: lockdep-checked RCU-protected pointer access::
>
> rcu_access_pointer
> rcu_dereference_raw
> @@ -976,6 +1003,7 @@ the right tool for your job.
>
>
> 8. ANSWERS TO QUICK QUIZZES
> +----------------------------
>
> Quick Quiz #1: Why is this argument naive? How could a deadlock
> occur when using this algorithm in a real-world Linux
>
Here, the formatting is not proper. In the rst file, the question should be
added in the next line after Quick Quiz #1. Currently, half of the question
appears in bold and the rest half does not.
Also, as followed in all the documents there should be a cross-reference to
the answer to this question. As this document is quite big having
references would be helpful.
The same applies to all other quick quiz questions in this document and in
the Answers section as well the questions do not appear properly, half in
bold text and half not bold.
Apart from this, the other added changes look good!
Thank you
Madhuparna
--
> 2.20.1
>
> _______________________________________________
> Linux-kernel-mentees mailing list
> Linux-kernel-mentees@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees
>
ᐧ
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_______________________________________________
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^ permalink raw reply [flat|nested] 23+ messages in thread
* [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-11-02 8:31 ` madhuparnabhowmik04
2019-11-02 8:31 ` Madhuparna Bhowmik
2019-11-02 8:31 ` Madhuparna Bhowmik
@ 2019-11-02 12:00 ` tranmanphong
2019-11-02 12:00 ` Phong Tran
2019-11-02 12:00 ` Phong Tran
2 siblings, 2 replies; 23+ messages in thread
From: tranmanphong @ 2019-11-02 12:00 UTC (permalink / raw)
On Sat, Nov 2, 2019 at 3:31 PM Madhuparna Bhowmik <
madhuparnabhowmik04 at gmail.com> wrote:
> I reviewed this patch, and I have the following suggestions:
>
> Thank for feedback. I did some change adding the cross-ref. patch sent
also apply in rcu-dev branch.
https://lists.linuxfoundation.org/pipermail/linux-kernel-mentees/2019-November/001019.html
Regards,
Phong.
> On Thu, Oct 31, 2019 at 5:04 AM Phong Tran <tranmanphong at gmail.com> wrote:
>
>> Sync the format with current state of kernel documentation.
>> This change base on rcu-dev branch
>> what changed:
>> - Format bullet lists
>> - Add literal blocks
>>
>> Signed-off-by: Phong Tran <tranmanphong at gmail.com>
>> ---
>> Documentation/RCU/index.rst | 1 +
>> .../RCU/{whatisRCU.txt => whatisRCU.rst} | 150 +++++++++++-------
>> 2 files changed, 90 insertions(+), 61 deletions(-)
>> rename Documentation/RCU/{whatisRCU.txt => whatisRCU.rst} (91%)
>>
>> diff --git a/Documentation/RCU/index.rst b/Documentation/RCU/index.rst
>> index 627128c230dc..b9b11481c727 100644
>> --- a/Documentation/RCU/index.rst
>> +++ b/Documentation/RCU/index.rst
>> @@ -8,6 +8,7 @@ RCU concepts
>> :maxdepth: 3
>>
>> arrayRCU
>> + whatisRCU
>> rcu
>> listRCU
>> NMI-RCU
>> diff --git a/Documentation/RCU/whatisRCU.txt
>> b/Documentation/RCU/whatisRCU.rst
>> similarity index 91%
>> rename from Documentation/RCU/whatisRCU.txt
>> rename to Documentation/RCU/whatisRCU.rst
>> index 58ba05c4d97f..70d0e4c21917 100644
>> --- a/Documentation/RCU/whatisRCU.txt
>> +++ b/Documentation/RCU/whatisRCU.rst
>> @@ -1,15 +1,18 @@
>> +.. _rcu_doc:
>> +
>> What is RCU? -- "Read, Copy, Update"
>> +======================================
>>
>> Please note that the "What is RCU?" LWN series is an excellent place
>> to start learning about RCU:
>>
>> -1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
>> -2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
>> -3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
>> -4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
>> - 2010 Big API Table http://lwn.net/Articles/419086/
>> -5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
>> - 2014 Big API Table http://lwn.net/Articles/609973/
>> +| 1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
>> +| 2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
>> +| 3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
>> +| 4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
>> +| 2010 Big API Table http://lwn.net/Articles/419086/
>> +| 5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
>> +| 2014 Big API Table http://lwn.net/Articles/609973/
>>
>>
> Adding an external link here would be better.
> like this : `text <link URL>`_
>
> What is RCU?
>> @@ -51,6 +54,7 @@ never need this document anyway. ;-)
>>
>>
>>
> There is a list of topics that are covered in this documentation.
> Like this:
>
> 1. RCU OVERVIEW
> 2. WHAT IS RCU?S CORE API?
> 3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
> 4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
> ...
>
> since this document is quite big adding cross-references to the above
> would be helpful.
>
>
>> 1. RCU OVERVIEW
>> +----------------
>>
>> The basic idea behind RCU is to split updates into "removal" and
>> "reclamation" phases. The removal phase removes references to data items
>> @@ -118,6 +122,7 @@ Read on to learn about how RCU's API makes this easy.
>>
>>
>> 2. WHAT IS RCU'S CORE API?
>> +---------------------------
>>
>> The core RCU API is quite small:
>>
>> @@ -166,7 +171,7 @@ synchronize_rcu()
>> read-side critical sections on all CPUs have completed.
>> Note that synchronize_rcu() will -not- necessarily wait for
>> any subsequent RCU read-side critical sections to complete.
>> - For example, consider the following sequence of events:
>> + For example, consider the following sequence of events::
>>
>> CPU 0 CPU 1 CPU 2
>> ----------------- ------------------------- ---------------
>> @@ -248,13 +253,13 @@ rcu_dereference()
>>
>> Common coding practice uses rcu_dereference() to copy an
>> RCU-protected pointer to a local variable, then dereferences
>> - this local variable, for example as follows:
>> + this local variable, for example as follows::
>>
>> p = rcu_dereference(head.next);
>> return p->data;
>>
>> However, in this case, one could just as easily combine these
>> - into one statement:
>> + into one statement::
>>
>> return rcu_dereference(head.next)->data;
>>
>> @@ -267,7 +272,7 @@ rcu_dereference()
>>
>> Note that the value returned by rcu_dereference() is valid
>> only within the enclosing RCU read-side critical section [1].
>> - For example, the following is -not- legal:
>> + For example, the following is -not- legal::
>>
>> rcu_read_lock();
>> p = rcu_dereference(head.next);
>> @@ -315,6 +320,7 @@ rcu_dereference()
>>
>> The following diagram shows how each API communicates among the
>> reader, updater, and reclaimer.
>> +::
>>
>>
>> rcu_assign_pointer()
>> @@ -377,10 +383,12 @@ for specialized uses, but are relatively uncommon.
>>
>>
>> 3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
>> +-----------------------------------------------
>>
>> This section shows a simple use of the core RCU API to protect a
>> global pointer to a dynamically allocated structure. More-typical
>> uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt.
>> +::
>>
>> struct foo {
>> int a;
>> @@ -467,13 +475,14 @@ arrayRCU.txt, and NMI-RCU.txt.
>>
>>
>> 4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
>> +--------------------------------------------
>>
>> In the example above, foo_update_a() blocks until a grace period elapses.
>> This is quite simple, but in some cases one cannot afford to wait so
>> long -- there might be other high-priority work to be done.
>>
>> In such cases, one uses call_rcu() rather than synchronize_rcu().
>> -The call_rcu() API is as follows:
>> +The call_rcu() API is as follows::
>>
>> void call_rcu(struct rcu_head * head,
>> void (*func)(struct rcu_head *head));
>> @@ -481,7 +490,7 @@ The call_rcu() API is as follows:
>> This function invokes func(head) after a grace period has elapsed.
>> This invocation might happen from either softirq or process context,
>> so the function is not permitted to block. The foo struct needs to
>> -have an rcu_head structure added, perhaps as follows:
>> +have an rcu_head structure added, perhaps as follows::
>>
>> struct foo {
>> int a;
>> @@ -490,7 +499,7 @@ have an rcu_head structure added, perhaps as follows:
>> struct rcu_head rcu;
>> };
>>
>> -The foo_update_a() function might then be written as follows:
>> +The foo_update_a() function might then be written as follows::
>>
>> /*
>> * Create a new struct foo that is the same as the one currently
>> @@ -520,7 +529,7 @@ The foo_update_a() function might then be written as
>> follows:
>> call_rcu(&old_fp->rcu, foo_reclaim);
>> }
>>
>> -The foo_reclaim() function might appear as follows:
>> +The foo_reclaim() function might appear as follows::
>>
>> void foo_reclaim(struct rcu_head *rp)
>> {
>> @@ -552,7 +561,7 @@ o Use call_rcu() -after- removing a data element
>> from an
>>
>> If the callback for call_rcu() is not doing anything more than calling
>> kfree() on the structure, you can use kfree_rcu() instead of call_rcu()
>> -to avoid having to write your own callback:
>> +to avoid having to write your own callback::
>>
>> kfree_rcu(old_fp, rcu);
>>
>> @@ -560,6 +569,7 @@ Again, see checklist.txt for additional rules
>> governing the use of RCU.
>>
>>
>> 5. WHAT ARE SOME SIMPLE IMPLEMENTATIONS OF RCU?
>> +------------------------------------------------
>>
>> One of the nice things about RCU is that it has extremely simple "toy"
>> implementations that are a good first step towards understanding the
>> @@ -591,7 +601,7 @@ you allow nested rcu_read_lock() calls, you can
>> deadlock.
>> However, it is probably the easiest implementation to relate to, so is
>> a good starting point.
>>
>> -It is extremely simple:
>> +It is extremely simple::
>>
>> static DEFINE_RWLOCK(rcu_gp_mutex);
>>
>> @@ -614,7 +624,7 @@ It is extremely simple:
>>
>> [You can ignore rcu_assign_pointer() and rcu_dereference() without
>> missing
>> much. But here are simplified versions anyway. And whatever you do,
>> -don't forget about them when submitting patches making use of RCU!]
>> +don't forget about them when submitting patches making use of RCU!]::
>>
>> #define rcu_assign_pointer(p, v) \
>> ({ \
>> @@ -659,6 +669,7 @@ This section presents a "toy" RCU implementation that
>> is based on
>> on features such as hotplug CPU and the ability to run in CONFIG_PREEMPT
>> kernels. The definitions of rcu_dereference() and rcu_assign_pointer()
>> are the same as those shown in the preceding section, so they are
>> omitted.
>> +::
>>
>> void rcu_read_lock(void) { }
>>
>> @@ -707,10 +718,12 @@ Quick Quiz #3: If it is illegal to block in an RCU
>> read-side
>>
>>
>> 6. ANALOGY WITH READER-WRITER LOCKING
>> +--------------------------------------
>>
>> Although RCU can be used in many different ways, a very common use of
>> RCU is analogous to reader-writer locking. The following unified
>> diff shows how closely related RCU and reader-writer locking can be.
>> +::
>>
>> @@ -5,5 +5,5 @@ struct el {
>> int data;
>> @@ -762,7 +775,7 @@ diff shows how closely related RCU and reader-writer
>> locking can be.
>> return 0;
>> }
>>
>> -Or, for those who prefer a side-by-side listing:
>> +Or, for those who prefer a side-by-side listing::
>>
>> 1 struct el { 1 struct el {
>> 2 struct list_head list; 2 struct list_head list;
>> @@ -774,40 +787,44 @@ Or, for those who prefer a side-by-side listing:
>> 8 rwlock_t listmutex; 8 spinlock_t listmutex;
>> 9 struct el head; 9 struct el head;
>>
>> - 1 int search(long key, int *result) 1 int search(long key, int
>> *result)
>> - 2 { 2 {
>> - 3 struct list_head *lp; 3 struct list_head *lp;
>> - 4 struct el *p; 4 struct el *p;
>> - 5 5
>> - 6 read_lock(&listmutex); 6 rcu_read_lock();
>> - 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
>> head, lp) {
>> - 8 if (p->key == key) { 8 if (p->key == key) {
>> - 9 *result = p->data; 9 *result = p->data;
>> -10 read_unlock(&listmutex); 10 rcu_read_unlock();
>> -11 return 1; 11 return 1;
>> -12 } 12 }
>> -13 } 13 }
>> -14 read_unlock(&listmutex); 14 rcu_read_unlock();
>> -15 return 0; 15 return 0;
>> -16 } 16 }
>> -
>> - 1 int delete(long key) 1 int delete(long key)
>> - 2 { 2 {
>> - 3 struct el *p; 3 struct el *p;
>> - 4 4
>> - 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
>> - 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p, head,
>> lp) {
>> - 7 if (p->key == key) { 7 if (p->key == key) {
>> - 8 list_del(&p->list); 8 list_del_rcu(&p->list);
>> - 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
>> - 10 synchronize_rcu();
>> -10 kfree(p); 11 kfree(p);
>> -11 return 1; 12 return 1;
>> -12 } 13 }
>> -13 } 14 }
>> -14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
>> -15 return 0; 16 return 0;
>> -16 } 17 }
>> +::
>> +
>> + 1 int search(long key, int *result) 1 int search(long key, int
>> *result)
>> + 2 { 2 {
>> + 3 struct list_head *lp; 3 struct list_head *lp;
>> + 4 struct el *p; 4 struct el *p;
>> + 5 5
>> + 6 read_lock(&listmutex); 6 rcu_read_lock();
>> + 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
>> head, lp) {
>> + 8 if (p->key == key) { 8 if (p->key == key) {
>> + 9 *result = p->data; 9 *result = p->data;
>> + 10 read_unlock(&listmutex); 10 rcu_read_unlock();
>> + 11 return 1; 11 return 1;
>> + 12 } 12 }
>> + 13 } 13 }
>> + 14 read_unlock(&listmutex); 14 rcu_read_unlock();
>> + 15 return 0; 15 return 0;
>> + 16 } 16 }
>> +
>> +::
>> +
>> + 1 int delete(long key) 1 int delete(long key)
>> + 2 { 2 {
>> + 3 struct el *p; 3 struct el *p;
>> + 4 4
>> + 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
>> + 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p,
>> head, lp) {
>> + 7 if (p->key == key) { 7 if (p->key == key) {
>> + 8 list_del(&p->list); 8 list_del_rcu(&p->list);
>> + 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
>> + 10 synchronize_rcu();
>> + 10 kfree(p); 11 kfree(p);
>> + 11 return 1; 12 return 1;
>> + 12 } 13 }
>> + 13 } 14 }
>> + 14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
>> + 15 return 0; 16 return 0;
>> + 16 } 17 }
>>
>> Either way, the differences are quite small. Read-side locking moves
>> to rcu_read_lock() and rcu_read_unlock, update-side locking moves from
>> @@ -827,13 +844,14 @@ be used in place of synchronize_rcu().
>>
>>
>> 7. FULL LIST OF RCU APIs
>> +-------------------------
>>
>> The RCU APIs are documented in docbook-format header comments in the
>> Linux-kernel source code, but it helps to have a full list of the
>> APIs, since there does not appear to be a way to categorize them
>> in docbook. Here is the list, by category.
>>
>> -RCU list traversal:
>> +RCU list traversal::
>>
>> list_entry_rcu
>> list_first_entry_rcu
>> @@ -854,7 +872,7 @@ RCU list traversal:
>> hlist_bl_first_rcu
>> hlist_bl_for_each_entry_rcu
>>
>> -RCU pointer/list update:
>> +RCU pointer/list udate::
>>
>> rcu_assign_pointer
>> list_add_rcu
>> @@ -876,7 +894,9 @@ RCU pointer/list update:
>> hlist_bl_del_rcu
>> hlist_bl_set_first_rcu
>>
>> -RCU: Critical sections Grace period Barrier
>> +RCU::
>> +
>> + Critical sections Grace period Barrier
>>
>> rcu_read_lock synchronize_net rcu_barrier
>> rcu_read_unlock synchronize_rcu
>> @@ -885,7 +905,9 @@ RCU: Critical sections Grace period
>> Barrier
>> rcu_dereference_check kfree_rcu
>> rcu_dereference_protected
>>
>> -bh: Critical sections Grace period Barrier
>> +bh::
>> +
>> + Critical sections Grace period Barrier
>>
>> rcu_read_lock_bh call_rcu rcu_barrier
>> rcu_read_unlock_bh synchronize_rcu
>> @@ -896,7 +918,9 @@ bh: Critical sections Grace period
>> Barrier
>> rcu_dereference_bh_protected
>> rcu_read_lock_bh_held
>>
>> -sched: Critical sections Grace period Barrier
>> +sched::
>> +
>> + Critical sections Grace period Barrier
>>
>> rcu_read_lock_sched call_rcu rcu_barrier
>> rcu_read_unlock_sched synchronize_rcu
>> @@ -910,7 +934,9 @@ sched: Critical sections Grace period
>> Barrier
>> rcu_read_lock_sched_held
>>
>>
>> -SRCU: Critical sections Grace period Barrier
>> +SRCU::
>> +
>> + Critical sections Grace period Barrier
>>
>> srcu_read_lock call_srcu srcu_barrier
>> srcu_read_unlock synchronize_srcu
>> @@ -918,13 +944,14 @@ SRCU: Critical sections Grace period
>> Barrier
>> srcu_dereference_check
>> srcu_read_lock_held
>>
>> -SRCU: Initialization/cleanup
>> +SRCU: Initialization/cleanup::
>> +
>> DEFINE_SRCU
>> DEFINE_STATIC_SRCU
>> init_srcu_struct
>> cleanup_srcu_struct
>>
>> -All: lockdep-checked RCU-protected pointer access
>> +All: lockdep-checked RCU-protected pointer access::
>>
>> rcu_access_pointer
>> rcu_dereference_raw
>> @@ -976,6 +1003,7 @@ the right tool for your job.
>>
>>
>> 8. ANSWERS TO QUICK QUIZZES
>> +----------------------------
>>
>> Quick Quiz #1: Why is this argument naive? How could a deadlock
>> occur when using this algorithm in a real-world Linux
>>
>
> Here, the formatting is not proper. In the rst file, the question should
> be added in the next line after Quick Quiz #1. Currently, half of the
> question appears in bold and the rest half does not.
> Also, as followed in all the documents there should be a cross-reference
> to the answer to this question. As this document is quite big having
> references would be helpful.
> The same applies to all other quick quiz questions in this document and in
> the Answers section as well the questions do not appear properly, half in
> bold text and half not bold.
>
> Apart from this, the other added changes look good!
>
> Thank you
> Madhuparna
>
> --
>> 2.20.1
>>
>> _______________________________________________
>> Linux-kernel-mentees mailing list
>> Linux-kernel-mentees at lists.linuxfoundation.org
>> https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees
>>
> ?
>
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* [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-11-02 12:00 ` tranmanphong
2019-11-02 12:00 ` Phong Tran
@ 2019-11-02 12:00 ` Phong Tran
1 sibling, 0 replies; 23+ messages in thread
From: Phong Tran @ 2019-11-02 12:00 UTC (permalink / raw)
On Sat, Nov 2, 2019 at 3:31 PM Madhuparna Bhowmik <
madhuparnabhowmik04 at gmail.com> wrote:
> I reviewed this patch, and I have the following suggestions:
>
> Thank for feedback. I did some change adding the cross-ref. patch sent
also apply in rcu-dev branch.
https://lists.linuxfoundation.org/pipermail/linux-kernel-mentees/2019-November/001019.html
Regards,
Phong.
> On Thu, Oct 31, 2019 at 5:04 AM Phong Tran <tranmanphong at gmail.com> wrote:
>
>> Sync the format with current state of kernel documentation.
>> This change base on rcu-dev branch
>> what changed:
>> - Format bullet lists
>> - Add literal blocks
>>
>> Signed-off-by: Phong Tran <tranmanphong at gmail.com>
>> ---
>> Documentation/RCU/index.rst | 1 +
>> .../RCU/{whatisRCU.txt => whatisRCU.rst} | 150 +++++++++++-------
>> 2 files changed, 90 insertions(+), 61 deletions(-)
>> rename Documentation/RCU/{whatisRCU.txt => whatisRCU.rst} (91%)
>>
>> diff --git a/Documentation/RCU/index.rst b/Documentation/RCU/index.rst
>> index 627128c230dc..b9b11481c727 100644
>> --- a/Documentation/RCU/index.rst
>> +++ b/Documentation/RCU/index.rst
>> @@ -8,6 +8,7 @@ RCU concepts
>> :maxdepth: 3
>>
>> arrayRCU
>> + whatisRCU
>> rcu
>> listRCU
>> NMI-RCU
>> diff --git a/Documentation/RCU/whatisRCU.txt
>> b/Documentation/RCU/whatisRCU.rst
>> similarity index 91%
>> rename from Documentation/RCU/whatisRCU.txt
>> rename to Documentation/RCU/whatisRCU.rst
>> index 58ba05c4d97f..70d0e4c21917 100644
>> --- a/Documentation/RCU/whatisRCU.txt
>> +++ b/Documentation/RCU/whatisRCU.rst
>> @@ -1,15 +1,18 @@
>> +.. _rcu_doc:
>> +
>> What is RCU? -- "Read, Copy, Update"
>> +======================================
>>
>> Please note that the "What is RCU?" LWN series is an excellent place
>> to start learning about RCU:
>>
>> -1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
>> -2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
>> -3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
>> -4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
>> - 2010 Big API Table http://lwn.net/Articles/419086/
>> -5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
>> - 2014 Big API Table http://lwn.net/Articles/609973/
>> +| 1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
>> +| 2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
>> +| 3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
>> +| 4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
>> +| 2010 Big API Table http://lwn.net/Articles/419086/
>> +| 5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
>> +| 2014 Big API Table http://lwn.net/Articles/609973/
>>
>>
> Adding an external link here would be better.
> like this : `text <link URL>`_
>
> What is RCU?
>> @@ -51,6 +54,7 @@ never need this document anyway. ;-)
>>
>>
>>
> There is a list of topics that are covered in this documentation.
> Like this:
>
> 1. RCU OVERVIEW
> 2. WHAT IS RCU?S CORE API?
> 3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
> 4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
> ...
>
> since this document is quite big adding cross-references to the above
> would be helpful.
>
>
>> 1. RCU OVERVIEW
>> +----------------
>>
>> The basic idea behind RCU is to split updates into "removal" and
>> "reclamation" phases. The removal phase removes references to data items
>> @@ -118,6 +122,7 @@ Read on to learn about how RCU's API makes this easy.
>>
>>
>> 2. WHAT IS RCU'S CORE API?
>> +---------------------------
>>
>> The core RCU API is quite small:
>>
>> @@ -166,7 +171,7 @@ synchronize_rcu()
>> read-side critical sections on all CPUs have completed.
>> Note that synchronize_rcu() will -not- necessarily wait for
>> any subsequent RCU read-side critical sections to complete.
>> - For example, consider the following sequence of events:
>> + For example, consider the following sequence of events::
>>
>> CPU 0 CPU 1 CPU 2
>> ----------------- ------------------------- ---------------
>> @@ -248,13 +253,13 @@ rcu_dereference()
>>
>> Common coding practice uses rcu_dereference() to copy an
>> RCU-protected pointer to a local variable, then dereferences
>> - this local variable, for example as follows:
>> + this local variable, for example as follows::
>>
>> p = rcu_dereference(head.next);
>> return p->data;
>>
>> However, in this case, one could just as easily combine these
>> - into one statement:
>> + into one statement::
>>
>> return rcu_dereference(head.next)->data;
>>
>> @@ -267,7 +272,7 @@ rcu_dereference()
>>
>> Note that the value returned by rcu_dereference() is valid
>> only within the enclosing RCU read-side critical section [1].
>> - For example, the following is -not- legal:
>> + For example, the following is -not- legal::
>>
>> rcu_read_lock();
>> p = rcu_dereference(head.next);
>> @@ -315,6 +320,7 @@ rcu_dereference()
>>
>> The following diagram shows how each API communicates among the
>> reader, updater, and reclaimer.
>> +::
>>
>>
>> rcu_assign_pointer()
>> @@ -377,10 +383,12 @@ for specialized uses, but are relatively uncommon.
>>
>>
>> 3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
>> +-----------------------------------------------
>>
>> This section shows a simple use of the core RCU API to protect a
>> global pointer to a dynamically allocated structure. More-typical
>> uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt.
>> +::
>>
>> struct foo {
>> int a;
>> @@ -467,13 +475,14 @@ arrayRCU.txt, and NMI-RCU.txt.
>>
>>
>> 4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
>> +--------------------------------------------
>>
>> In the example above, foo_update_a() blocks until a grace period elapses.
>> This is quite simple, but in some cases one cannot afford to wait so
>> long -- there might be other high-priority work to be done.
>>
>> In such cases, one uses call_rcu() rather than synchronize_rcu().
>> -The call_rcu() API is as follows:
>> +The call_rcu() API is as follows::
>>
>> void call_rcu(struct rcu_head * head,
>> void (*func)(struct rcu_head *head));
>> @@ -481,7 +490,7 @@ The call_rcu() API is as follows:
>> This function invokes func(head) after a grace period has elapsed.
>> This invocation might happen from either softirq or process context,
>> so the function is not permitted to block. The foo struct needs to
>> -have an rcu_head structure added, perhaps as follows:
>> +have an rcu_head structure added, perhaps as follows::
>>
>> struct foo {
>> int a;
>> @@ -490,7 +499,7 @@ have an rcu_head structure added, perhaps as follows:
>> struct rcu_head rcu;
>> };
>>
>> -The foo_update_a() function might then be written as follows:
>> +The foo_update_a() function might then be written as follows::
>>
>> /*
>> * Create a new struct foo that is the same as the one currently
>> @@ -520,7 +529,7 @@ The foo_update_a() function might then be written as
>> follows:
>> call_rcu(&old_fp->rcu, foo_reclaim);
>> }
>>
>> -The foo_reclaim() function might appear as follows:
>> +The foo_reclaim() function might appear as follows::
>>
>> void foo_reclaim(struct rcu_head *rp)
>> {
>> @@ -552,7 +561,7 @@ o Use call_rcu() -after- removing a data element
>> from an
>>
>> If the callback for call_rcu() is not doing anything more than calling
>> kfree() on the structure, you can use kfree_rcu() instead of call_rcu()
>> -to avoid having to write your own callback:
>> +to avoid having to write your own callback::
>>
>> kfree_rcu(old_fp, rcu);
>>
>> @@ -560,6 +569,7 @@ Again, see checklist.txt for additional rules
>> governing the use of RCU.
>>
>>
>> 5. WHAT ARE SOME SIMPLE IMPLEMENTATIONS OF RCU?
>> +------------------------------------------------
>>
>> One of the nice things about RCU is that it has extremely simple "toy"
>> implementations that are a good first step towards understanding the
>> @@ -591,7 +601,7 @@ you allow nested rcu_read_lock() calls, you can
>> deadlock.
>> However, it is probably the easiest implementation to relate to, so is
>> a good starting point.
>>
>> -It is extremely simple:
>> +It is extremely simple::
>>
>> static DEFINE_RWLOCK(rcu_gp_mutex);
>>
>> @@ -614,7 +624,7 @@ It is extremely simple:
>>
>> [You can ignore rcu_assign_pointer() and rcu_dereference() without
>> missing
>> much. But here are simplified versions anyway. And whatever you do,
>> -don't forget about them when submitting patches making use of RCU!]
>> +don't forget about them when submitting patches making use of RCU!]::
>>
>> #define rcu_assign_pointer(p, v) \
>> ({ \
>> @@ -659,6 +669,7 @@ This section presents a "toy" RCU implementation that
>> is based on
>> on features such as hotplug CPU and the ability to run in CONFIG_PREEMPT
>> kernels. The definitions of rcu_dereference() and rcu_assign_pointer()
>> are the same as those shown in the preceding section, so they are
>> omitted.
>> +::
>>
>> void rcu_read_lock(void) { }
>>
>> @@ -707,10 +718,12 @@ Quick Quiz #3: If it is illegal to block in an RCU
>> read-side
>>
>>
>> 6. ANALOGY WITH READER-WRITER LOCKING
>> +--------------------------------------
>>
>> Although RCU can be used in many different ways, a very common use of
>> RCU is analogous to reader-writer locking. The following unified
>> diff shows how closely related RCU and reader-writer locking can be.
>> +::
>>
>> @@ -5,5 +5,5 @@ struct el {
>> int data;
>> @@ -762,7 +775,7 @@ diff shows how closely related RCU and reader-writer
>> locking can be.
>> return 0;
>> }
>>
>> -Or, for those who prefer a side-by-side listing:
>> +Or, for those who prefer a side-by-side listing::
>>
>> 1 struct el { 1 struct el {
>> 2 struct list_head list; 2 struct list_head list;
>> @@ -774,40 +787,44 @@ Or, for those who prefer a side-by-side listing:
>> 8 rwlock_t listmutex; 8 spinlock_t listmutex;
>> 9 struct el head; 9 struct el head;
>>
>> - 1 int search(long key, int *result) 1 int search(long key, int
>> *result)
>> - 2 { 2 {
>> - 3 struct list_head *lp; 3 struct list_head *lp;
>> - 4 struct el *p; 4 struct el *p;
>> - 5 5
>> - 6 read_lock(&listmutex); 6 rcu_read_lock();
>> - 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
>> head, lp) {
>> - 8 if (p->key == key) { 8 if (p->key == key) {
>> - 9 *result = p->data; 9 *result = p->data;
>> -10 read_unlock(&listmutex); 10 rcu_read_unlock();
>> -11 return 1; 11 return 1;
>> -12 } 12 }
>> -13 } 13 }
>> -14 read_unlock(&listmutex); 14 rcu_read_unlock();
>> -15 return 0; 15 return 0;
>> -16 } 16 }
>> -
>> - 1 int delete(long key) 1 int delete(long key)
>> - 2 { 2 {
>> - 3 struct el *p; 3 struct el *p;
>> - 4 4
>> - 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
>> - 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p, head,
>> lp) {
>> - 7 if (p->key == key) { 7 if (p->key == key) {
>> - 8 list_del(&p->list); 8 list_del_rcu(&p->list);
>> - 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
>> - 10 synchronize_rcu();
>> -10 kfree(p); 11 kfree(p);
>> -11 return 1; 12 return 1;
>> -12 } 13 }
>> -13 } 14 }
>> -14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
>> -15 return 0; 16 return 0;
>> -16 } 17 }
>> +::
>> +
>> + 1 int search(long key, int *result) 1 int search(long key, int
>> *result)
>> + 2 { 2 {
>> + 3 struct list_head *lp; 3 struct list_head *lp;
>> + 4 struct el *p; 4 struct el *p;
>> + 5 5
>> + 6 read_lock(&listmutex); 6 rcu_read_lock();
>> + 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
>> head, lp) {
>> + 8 if (p->key == key) { 8 if (p->key == key) {
>> + 9 *result = p->data; 9 *result = p->data;
>> + 10 read_unlock(&listmutex); 10 rcu_read_unlock();
>> + 11 return 1; 11 return 1;
>> + 12 } 12 }
>> + 13 } 13 }
>> + 14 read_unlock(&listmutex); 14 rcu_read_unlock();
>> + 15 return 0; 15 return 0;
>> + 16 } 16 }
>> +
>> +::
>> +
>> + 1 int delete(long key) 1 int delete(long key)
>> + 2 { 2 {
>> + 3 struct el *p; 3 struct el *p;
>> + 4 4
>> + 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
>> + 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p,
>> head, lp) {
>> + 7 if (p->key == key) { 7 if (p->key == key) {
>> + 8 list_del(&p->list); 8 list_del_rcu(&p->list);
>> + 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
>> + 10 synchronize_rcu();
>> + 10 kfree(p); 11 kfree(p);
>> + 11 return 1; 12 return 1;
>> + 12 } 13 }
>> + 13 } 14 }
>> + 14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
>> + 15 return 0; 16 return 0;
>> + 16 } 17 }
>>
>> Either way, the differences are quite small. Read-side locking moves
>> to rcu_read_lock() and rcu_read_unlock, update-side locking moves from
>> @@ -827,13 +844,14 @@ be used in place of synchronize_rcu().
>>
>>
>> 7. FULL LIST OF RCU APIs
>> +-------------------------
>>
>> The RCU APIs are documented in docbook-format header comments in the
>> Linux-kernel source code, but it helps to have a full list of the
>> APIs, since there does not appear to be a way to categorize them
>> in docbook. Here is the list, by category.
>>
>> -RCU list traversal:
>> +RCU list traversal::
>>
>> list_entry_rcu
>> list_first_entry_rcu
>> @@ -854,7 +872,7 @@ RCU list traversal:
>> hlist_bl_first_rcu
>> hlist_bl_for_each_entry_rcu
>>
>> -RCU pointer/list update:
>> +RCU pointer/list udate::
>>
>> rcu_assign_pointer
>> list_add_rcu
>> @@ -876,7 +894,9 @@ RCU pointer/list update:
>> hlist_bl_del_rcu
>> hlist_bl_set_first_rcu
>>
>> -RCU: Critical sections Grace period Barrier
>> +RCU::
>> +
>> + Critical sections Grace period Barrier
>>
>> rcu_read_lock synchronize_net rcu_barrier
>> rcu_read_unlock synchronize_rcu
>> @@ -885,7 +905,9 @@ RCU: Critical sections Grace period
>> Barrier
>> rcu_dereference_check kfree_rcu
>> rcu_dereference_protected
>>
>> -bh: Critical sections Grace period Barrier
>> +bh::
>> +
>> + Critical sections Grace period Barrier
>>
>> rcu_read_lock_bh call_rcu rcu_barrier
>> rcu_read_unlock_bh synchronize_rcu
>> @@ -896,7 +918,9 @@ bh: Critical sections Grace period
>> Barrier
>> rcu_dereference_bh_protected
>> rcu_read_lock_bh_held
>>
>> -sched: Critical sections Grace period Barrier
>> +sched::
>> +
>> + Critical sections Grace period Barrier
>>
>> rcu_read_lock_sched call_rcu rcu_barrier
>> rcu_read_unlock_sched synchronize_rcu
>> @@ -910,7 +934,9 @@ sched: Critical sections Grace period
>> Barrier
>> rcu_read_lock_sched_held
>>
>>
>> -SRCU: Critical sections Grace period Barrier
>> +SRCU::
>> +
>> + Critical sections Grace period Barrier
>>
>> srcu_read_lock call_srcu srcu_barrier
>> srcu_read_unlock synchronize_srcu
>> @@ -918,13 +944,14 @@ SRCU: Critical sections Grace period
>> Barrier
>> srcu_dereference_check
>> srcu_read_lock_held
>>
>> -SRCU: Initialization/cleanup
>> +SRCU: Initialization/cleanup::
>> +
>> DEFINE_SRCU
>> DEFINE_STATIC_SRCU
>> init_srcu_struct
>> cleanup_srcu_struct
>>
>> -All: lockdep-checked RCU-protected pointer access
>> +All: lockdep-checked RCU-protected pointer access::
>>
>> rcu_access_pointer
>> rcu_dereference_raw
>> @@ -976,6 +1003,7 @@ the right tool for your job.
>>
>>
>> 8. ANSWERS TO QUICK QUIZZES
>> +----------------------------
>>
>> Quick Quiz #1: Why is this argument naive? How could a deadlock
>> occur when using this algorithm in a real-world Linux
>>
>
> Here, the formatting is not proper. In the rst file, the question should
> be added in the next line after Quick Quiz #1. Currently, half of the
> question appears in bold and the rest half does not.
> Also, as followed in all the documents there should be a cross-reference
> to the answer to this question. As this document is quite big having
> references would be helpful.
> The same applies to all other quick quiz questions in this document and in
> the Answers section as well the questions do not appear properly, half in
> bold text and half not bold.
>
> Apart from this, the other added changes look good!
>
> Thank you
> Madhuparna
>
> --
>> 2.20.1
>>
>> _______________________________________________
>> Linux-kernel-mentees mailing list
>> Linux-kernel-mentees at lists.linuxfoundation.org
>> https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees
>>
> ?
>
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* Re: [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst
2019-11-02 12:00 ` tranmanphong
@ 2019-11-02 12:00 ` Phong Tran
2019-11-02 12:00 ` Phong Tran
1 sibling, 0 replies; 23+ messages in thread
From: Phong Tran @ 2019-11-02 12:00 UTC (permalink / raw)
To: Madhuparna Bhowmik
Cc: paulmck, Jonathan Corbet, linux-doc, jiangshanlai, josh, rostedt,
linux-kernel, rcu, mathieu.desnoyers, Joel Fernandes,
linux-kernel-mentees
[-- Attachment #1.1: Type: text/plain, Size: 19569 bytes --]
On Sat, Nov 2, 2019 at 3:31 PM Madhuparna Bhowmik <
madhuparnabhowmik04@gmail.com> wrote:
> I reviewed this patch, and I have the following suggestions:
>
> Thank for feedback. I did some change adding the cross-ref. patch sent
also apply in rcu-dev branch.
https://lists.linuxfoundation.org/pipermail/linux-kernel-mentees/2019-November/001019.html
Regards,
Phong.
> On Thu, Oct 31, 2019 at 5:04 AM Phong Tran <tranmanphong@gmail.com> wrote:
>
>> Sync the format with current state of kernel documentation.
>> This change base on rcu-dev branch
>> what changed:
>> - Format bullet lists
>> - Add literal blocks
>>
>> Signed-off-by: Phong Tran <tranmanphong@gmail.com>
>> ---
>> Documentation/RCU/index.rst | 1 +
>> .../RCU/{whatisRCU.txt => whatisRCU.rst} | 150 +++++++++++-------
>> 2 files changed, 90 insertions(+), 61 deletions(-)
>> rename Documentation/RCU/{whatisRCU.txt => whatisRCU.rst} (91%)
>>
>> diff --git a/Documentation/RCU/index.rst b/Documentation/RCU/index.rst
>> index 627128c230dc..b9b11481c727 100644
>> --- a/Documentation/RCU/index.rst
>> +++ b/Documentation/RCU/index.rst
>> @@ -8,6 +8,7 @@ RCU concepts
>> :maxdepth: 3
>>
>> arrayRCU
>> + whatisRCU
>> rcu
>> listRCU
>> NMI-RCU
>> diff --git a/Documentation/RCU/whatisRCU.txt
>> b/Documentation/RCU/whatisRCU.rst
>> similarity index 91%
>> rename from Documentation/RCU/whatisRCU.txt
>> rename to Documentation/RCU/whatisRCU.rst
>> index 58ba05c4d97f..70d0e4c21917 100644
>> --- a/Documentation/RCU/whatisRCU.txt
>> +++ b/Documentation/RCU/whatisRCU.rst
>> @@ -1,15 +1,18 @@
>> +.. _rcu_doc:
>> +
>> What is RCU? -- "Read, Copy, Update"
>> +======================================
>>
>> Please note that the "What is RCU?" LWN series is an excellent place
>> to start learning about RCU:
>>
>> -1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
>> -2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
>> -3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
>> -4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
>> - 2010 Big API Table http://lwn.net/Articles/419086/
>> -5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
>> - 2014 Big API Table http://lwn.net/Articles/609973/
>> +| 1. What is RCU, Fundamentally? http://lwn.net/Articles/262464/
>> +| 2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
>> +| 3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
>> +| 4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
>> +| 2010 Big API Table http://lwn.net/Articles/419086/
>> +| 5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
>> +| 2014 Big API Table http://lwn.net/Articles/609973/
>>
>>
> Adding an external link here would be better.
> like this : `text <link URL>`_
>
> What is RCU?
>> @@ -51,6 +54,7 @@ never need this document anyway. ;-)
>>
>>
>>
> There is a list of topics that are covered in this documentation.
> Like this:
>
> 1. RCU OVERVIEW
> 2. WHAT IS RCU’S CORE API?
> 3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
> 4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
> ...
>
> since this document is quite big adding cross-references to the above
> would be helpful.
>
>
>> 1. RCU OVERVIEW
>> +----------------
>>
>> The basic idea behind RCU is to split updates into "removal" and
>> "reclamation" phases. The removal phase removes references to data items
>> @@ -118,6 +122,7 @@ Read on to learn about how RCU's API makes this easy.
>>
>>
>> 2. WHAT IS RCU'S CORE API?
>> +---------------------------
>>
>> The core RCU API is quite small:
>>
>> @@ -166,7 +171,7 @@ synchronize_rcu()
>> read-side critical sections on all CPUs have completed.
>> Note that synchronize_rcu() will -not- necessarily wait for
>> any subsequent RCU read-side critical sections to complete.
>> - For example, consider the following sequence of events:
>> + For example, consider the following sequence of events::
>>
>> CPU 0 CPU 1 CPU 2
>> ----------------- ------------------------- ---------------
>> @@ -248,13 +253,13 @@ rcu_dereference()
>>
>> Common coding practice uses rcu_dereference() to copy an
>> RCU-protected pointer to a local variable, then dereferences
>> - this local variable, for example as follows:
>> + this local variable, for example as follows::
>>
>> p = rcu_dereference(head.next);
>> return p->data;
>>
>> However, in this case, one could just as easily combine these
>> - into one statement:
>> + into one statement::
>>
>> return rcu_dereference(head.next)->data;
>>
>> @@ -267,7 +272,7 @@ rcu_dereference()
>>
>> Note that the value returned by rcu_dereference() is valid
>> only within the enclosing RCU read-side critical section [1].
>> - For example, the following is -not- legal:
>> + For example, the following is -not- legal::
>>
>> rcu_read_lock();
>> p = rcu_dereference(head.next);
>> @@ -315,6 +320,7 @@ rcu_dereference()
>>
>> The following diagram shows how each API communicates among the
>> reader, updater, and reclaimer.
>> +::
>>
>>
>> rcu_assign_pointer()
>> @@ -377,10 +383,12 @@ for specialized uses, but are relatively uncommon.
>>
>>
>> 3. WHAT ARE SOME EXAMPLE USES OF CORE RCU API?
>> +-----------------------------------------------
>>
>> This section shows a simple use of the core RCU API to protect a
>> global pointer to a dynamically allocated structure. More-typical
>> uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt.
>> +::
>>
>> struct foo {
>> int a;
>> @@ -467,13 +475,14 @@ arrayRCU.txt, and NMI-RCU.txt.
>>
>>
>> 4. WHAT IF MY UPDATING THREAD CANNOT BLOCK?
>> +--------------------------------------------
>>
>> In the example above, foo_update_a() blocks until a grace period elapses.
>> This is quite simple, but in some cases one cannot afford to wait so
>> long -- there might be other high-priority work to be done.
>>
>> In such cases, one uses call_rcu() rather than synchronize_rcu().
>> -The call_rcu() API is as follows:
>> +The call_rcu() API is as follows::
>>
>> void call_rcu(struct rcu_head * head,
>> void (*func)(struct rcu_head *head));
>> @@ -481,7 +490,7 @@ The call_rcu() API is as follows:
>> This function invokes func(head) after a grace period has elapsed.
>> This invocation might happen from either softirq or process context,
>> so the function is not permitted to block. The foo struct needs to
>> -have an rcu_head structure added, perhaps as follows:
>> +have an rcu_head structure added, perhaps as follows::
>>
>> struct foo {
>> int a;
>> @@ -490,7 +499,7 @@ have an rcu_head structure added, perhaps as follows:
>> struct rcu_head rcu;
>> };
>>
>> -The foo_update_a() function might then be written as follows:
>> +The foo_update_a() function might then be written as follows::
>>
>> /*
>> * Create a new struct foo that is the same as the one currently
>> @@ -520,7 +529,7 @@ The foo_update_a() function might then be written as
>> follows:
>> call_rcu(&old_fp->rcu, foo_reclaim);
>> }
>>
>> -The foo_reclaim() function might appear as follows:
>> +The foo_reclaim() function might appear as follows::
>>
>> void foo_reclaim(struct rcu_head *rp)
>> {
>> @@ -552,7 +561,7 @@ o Use call_rcu() -after- removing a data element
>> from an
>>
>> If the callback for call_rcu() is not doing anything more than calling
>> kfree() on the structure, you can use kfree_rcu() instead of call_rcu()
>> -to avoid having to write your own callback:
>> +to avoid having to write your own callback::
>>
>> kfree_rcu(old_fp, rcu);
>>
>> @@ -560,6 +569,7 @@ Again, see checklist.txt for additional rules
>> governing the use of RCU.
>>
>>
>> 5. WHAT ARE SOME SIMPLE IMPLEMENTATIONS OF RCU?
>> +------------------------------------------------
>>
>> One of the nice things about RCU is that it has extremely simple "toy"
>> implementations that are a good first step towards understanding the
>> @@ -591,7 +601,7 @@ you allow nested rcu_read_lock() calls, you can
>> deadlock.
>> However, it is probably the easiest implementation to relate to, so is
>> a good starting point.
>>
>> -It is extremely simple:
>> +It is extremely simple::
>>
>> static DEFINE_RWLOCK(rcu_gp_mutex);
>>
>> @@ -614,7 +624,7 @@ It is extremely simple:
>>
>> [You can ignore rcu_assign_pointer() and rcu_dereference() without
>> missing
>> much. But here are simplified versions anyway. And whatever you do,
>> -don't forget about them when submitting patches making use of RCU!]
>> +don't forget about them when submitting patches making use of RCU!]::
>>
>> #define rcu_assign_pointer(p, v) \
>> ({ \
>> @@ -659,6 +669,7 @@ This section presents a "toy" RCU implementation that
>> is based on
>> on features such as hotplug CPU and the ability to run in CONFIG_PREEMPT
>> kernels. The definitions of rcu_dereference() and rcu_assign_pointer()
>> are the same as those shown in the preceding section, so they are
>> omitted.
>> +::
>>
>> void rcu_read_lock(void) { }
>>
>> @@ -707,10 +718,12 @@ Quick Quiz #3: If it is illegal to block in an RCU
>> read-side
>>
>>
>> 6. ANALOGY WITH READER-WRITER LOCKING
>> +--------------------------------------
>>
>> Although RCU can be used in many different ways, a very common use of
>> RCU is analogous to reader-writer locking. The following unified
>> diff shows how closely related RCU and reader-writer locking can be.
>> +::
>>
>> @@ -5,5 +5,5 @@ struct el {
>> int data;
>> @@ -762,7 +775,7 @@ diff shows how closely related RCU and reader-writer
>> locking can be.
>> return 0;
>> }
>>
>> -Or, for those who prefer a side-by-side listing:
>> +Or, for those who prefer a side-by-side listing::
>>
>> 1 struct el { 1 struct el {
>> 2 struct list_head list; 2 struct list_head list;
>> @@ -774,40 +787,44 @@ Or, for those who prefer a side-by-side listing:
>> 8 rwlock_t listmutex; 8 spinlock_t listmutex;
>> 9 struct el head; 9 struct el head;
>>
>> - 1 int search(long key, int *result) 1 int search(long key, int
>> *result)
>> - 2 { 2 {
>> - 3 struct list_head *lp; 3 struct list_head *lp;
>> - 4 struct el *p; 4 struct el *p;
>> - 5 5
>> - 6 read_lock(&listmutex); 6 rcu_read_lock();
>> - 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
>> head, lp) {
>> - 8 if (p->key == key) { 8 if (p->key == key) {
>> - 9 *result = p->data; 9 *result = p->data;
>> -10 read_unlock(&listmutex); 10 rcu_read_unlock();
>> -11 return 1; 11 return 1;
>> -12 } 12 }
>> -13 } 13 }
>> -14 read_unlock(&listmutex); 14 rcu_read_unlock();
>> -15 return 0; 15 return 0;
>> -16 } 16 }
>> -
>> - 1 int delete(long key) 1 int delete(long key)
>> - 2 { 2 {
>> - 3 struct el *p; 3 struct el *p;
>> - 4 4
>> - 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
>> - 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p, head,
>> lp) {
>> - 7 if (p->key == key) { 7 if (p->key == key) {
>> - 8 list_del(&p->list); 8 list_del_rcu(&p->list);
>> - 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
>> - 10 synchronize_rcu();
>> -10 kfree(p); 11 kfree(p);
>> -11 return 1; 12 return 1;
>> -12 } 13 }
>> -13 } 14 }
>> -14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
>> -15 return 0; 16 return 0;
>> -16 } 17 }
>> +::
>> +
>> + 1 int search(long key, int *result) 1 int search(long key, int
>> *result)
>> + 2 { 2 {
>> + 3 struct list_head *lp; 3 struct list_head *lp;
>> + 4 struct el *p; 4 struct el *p;
>> + 5 5
>> + 6 read_lock(&listmutex); 6 rcu_read_lock();
>> + 7 list_for_each_entry(p, head, lp) { 7 list_for_each_entry_rcu(p,
>> head, lp) {
>> + 8 if (p->key == key) { 8 if (p->key == key) {
>> + 9 *result = p->data; 9 *result = p->data;
>> + 10 read_unlock(&listmutex); 10 rcu_read_unlock();
>> + 11 return 1; 11 return 1;
>> + 12 } 12 }
>> + 13 } 13 }
>> + 14 read_unlock(&listmutex); 14 rcu_read_unlock();
>> + 15 return 0; 15 return 0;
>> + 16 } 16 }
>> +
>> +::
>> +
>> + 1 int delete(long key) 1 int delete(long key)
>> + 2 { 2 {
>> + 3 struct el *p; 3 struct el *p;
>> + 4 4
>> + 5 write_lock(&listmutex); 5 spin_lock(&listmutex);
>> + 6 list_for_each_entry(p, head, lp) { 6 list_for_each_entry(p,
>> head, lp) {
>> + 7 if (p->key == key) { 7 if (p->key == key) {
>> + 8 list_del(&p->list); 8 list_del_rcu(&p->list);
>> + 9 write_unlock(&listmutex); 9 spin_unlock(&listmutex);
>> + 10 synchronize_rcu();
>> + 10 kfree(p); 11 kfree(p);
>> + 11 return 1; 12 return 1;
>> + 12 } 13 }
>> + 13 } 14 }
>> + 14 write_unlock(&listmutex); 15 spin_unlock(&listmutex);
>> + 15 return 0; 16 return 0;
>> + 16 } 17 }
>>
>> Either way, the differences are quite small. Read-side locking moves
>> to rcu_read_lock() and rcu_read_unlock, update-side locking moves from
>> @@ -827,13 +844,14 @@ be used in place of synchronize_rcu().
>>
>>
>> 7. FULL LIST OF RCU APIs
>> +-------------------------
>>
>> The RCU APIs are documented in docbook-format header comments in the
>> Linux-kernel source code, but it helps to have a full list of the
>> APIs, since there does not appear to be a way to categorize them
>> in docbook. Here is the list, by category.
>>
>> -RCU list traversal:
>> +RCU list traversal::
>>
>> list_entry_rcu
>> list_first_entry_rcu
>> @@ -854,7 +872,7 @@ RCU list traversal:
>> hlist_bl_first_rcu
>> hlist_bl_for_each_entry_rcu
>>
>> -RCU pointer/list update:
>> +RCU pointer/list udate::
>>
>> rcu_assign_pointer
>> list_add_rcu
>> @@ -876,7 +894,9 @@ RCU pointer/list update:
>> hlist_bl_del_rcu
>> hlist_bl_set_first_rcu
>>
>> -RCU: Critical sections Grace period Barrier
>> +RCU::
>> +
>> + Critical sections Grace period Barrier
>>
>> rcu_read_lock synchronize_net rcu_barrier
>> rcu_read_unlock synchronize_rcu
>> @@ -885,7 +905,9 @@ RCU: Critical sections Grace period
>> Barrier
>> rcu_dereference_check kfree_rcu
>> rcu_dereference_protected
>>
>> -bh: Critical sections Grace period Barrier
>> +bh::
>> +
>> + Critical sections Grace period Barrier
>>
>> rcu_read_lock_bh call_rcu rcu_barrier
>> rcu_read_unlock_bh synchronize_rcu
>> @@ -896,7 +918,9 @@ bh: Critical sections Grace period
>> Barrier
>> rcu_dereference_bh_protected
>> rcu_read_lock_bh_held
>>
>> -sched: Critical sections Grace period Barrier
>> +sched::
>> +
>> + Critical sections Grace period Barrier
>>
>> rcu_read_lock_sched call_rcu rcu_barrier
>> rcu_read_unlock_sched synchronize_rcu
>> @@ -910,7 +934,9 @@ sched: Critical sections Grace period
>> Barrier
>> rcu_read_lock_sched_held
>>
>>
>> -SRCU: Critical sections Grace period Barrier
>> +SRCU::
>> +
>> + Critical sections Grace period Barrier
>>
>> srcu_read_lock call_srcu srcu_barrier
>> srcu_read_unlock synchronize_srcu
>> @@ -918,13 +944,14 @@ SRCU: Critical sections Grace period
>> Barrier
>> srcu_dereference_check
>> srcu_read_lock_held
>>
>> -SRCU: Initialization/cleanup
>> +SRCU: Initialization/cleanup::
>> +
>> DEFINE_SRCU
>> DEFINE_STATIC_SRCU
>> init_srcu_struct
>> cleanup_srcu_struct
>>
>> -All: lockdep-checked RCU-protected pointer access
>> +All: lockdep-checked RCU-protected pointer access::
>>
>> rcu_access_pointer
>> rcu_dereference_raw
>> @@ -976,6 +1003,7 @@ the right tool for your job.
>>
>>
>> 8. ANSWERS TO QUICK QUIZZES
>> +----------------------------
>>
>> Quick Quiz #1: Why is this argument naive? How could a deadlock
>> occur when using this algorithm in a real-world Linux
>>
>
> Here, the formatting is not proper. In the rst file, the question should
> be added in the next line after Quick Quiz #1. Currently, half of the
> question appears in bold and the rest half does not.
> Also, as followed in all the documents there should be a cross-reference
> to the answer to this question. As this document is quite big having
> references would be helpful.
> The same applies to all other quick quiz questions in this document and in
> the Answers section as well the questions do not appear properly, half in
> bold text and half not bold.
>
> Apart from this, the other added changes look good!
>
> Thank you
> Madhuparna
>
> --
>> 2.20.1
>>
>> _______________________________________________
>> Linux-kernel-mentees mailing list
>> Linux-kernel-mentees@lists.linuxfoundation.org
>> https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees
>>
> ᐧ
>
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2019-10-30 23:31 [Linux-kernel-mentees] [PATCH] Doc: convert whatisRCU.txt to rst tranmanphong
2019-10-30 23:31 ` Phong Tran
2019-10-31 22:54 ` paulmck
2019-10-31 22:54 ` Paul E. McKenney
2019-10-31 22:54 ` Paul E. McKenney
2019-11-01 1:17 ` tranmanphong
2019-11-01 1:17 ` Phong Tran
2019-11-01 1:17 ` Phong Tran
2019-11-01 7:53 ` paulmck
2019-11-01 7:53 ` Paul E. McKenney
2019-11-01 7:53 ` Paul E. McKenney
2019-11-01 3:33 ` madhuparnabhowmik04
2019-11-01 3:33 ` Madhuparna Bhowmik
2019-11-01 3:33 ` Madhuparna Bhowmik
2019-11-01 7:53 ` paulmck
2019-11-01 7:53 ` Paul E. McKenney
2019-11-01 7:53 ` Paul E. McKenney
2019-11-02 8:31 ` madhuparnabhowmik04
2019-11-02 8:31 ` Madhuparna Bhowmik
2019-11-02 8:31 ` Madhuparna Bhowmik
2019-11-02 12:00 ` tranmanphong
2019-11-02 12:00 ` Phong Tran
2019-11-02 12:00 ` Phong Tran
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