From: Amol Grover <frextrite@gmail.com>
To: "Paul E. McKenney" <paulmck@kernel.org>,
Josh Triplett <josh@joshtriplett.org>,
Steven Rostedt <rostedt@goodmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Joel Fernandes <joel@joelfernandes.org>,
Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
rcu@vger.kernel.org, Joel Fernandes <joel@joelfernandes.org>,
linux-kernel-mentees@lists.linuxfoundation.org
Subject: [Linux-kernel-mentees] [PATCH] Documentation: RCU: whatisRCU: Fix formatting for section 2
Date: Mon, 4 Nov 2019 19:03:15 +0530 [thread overview]
Message-ID: <20191104133315.GA14499@workstation-kernel-dev> (raw)
Convert RCU API method text to sub-headings and
add hyperlink and superscript to 2 literary notes
under rcu_dereference() section
Signed-off-by: Amol Grover <frextrite@gmail.com>
---
Documentation/RCU/whatisRCU.rst | 34 +++++++++++++++++++++++++++------
1 file changed, 28 insertions(+), 6 deletions(-)
diff --git a/Documentation/RCU/whatisRCU.rst b/Documentation/RCU/whatisRCU.rst
index ae40c8bcc56c..3cf6e17d0065 100644
--- a/Documentation/RCU/whatisRCU.rst
+++ b/Documentation/RCU/whatisRCU.rst
@@ -150,6 +150,7 @@ later. See the kernel docbook documentation for more info, or look directly
at the function header comments.
rcu_read_lock()
+^^^^^^^^^^^^^^^
void rcu_read_lock(void);
@@ -164,6 +165,7 @@ rcu_read_lock()
longer-term references to data structures.
rcu_read_unlock()
+^^^^^^^^^^^^^^^^^
void rcu_read_unlock(void);
@@ -172,6 +174,7 @@ rcu_read_unlock()
read-side critical sections may be nested and/or overlapping.
synchronize_rcu()
+^^^^^^^^^^^^^^^^^
void synchronize_rcu(void);
@@ -225,6 +228,7 @@ synchronize_rcu()
checklist.txt for some approaches to limiting the update rate.
rcu_assign_pointer()
+^^^^^^^^^^^^^^^^^^^^
void rcu_assign_pointer(p, typeof(p) v);
@@ -245,6 +249,7 @@ rcu_assign_pointer()
the _rcu list-manipulation primitives such as list_add_rcu().
rcu_dereference()
+^^^^^^^^^^^^^^^^^
typeof(p) rcu_dereference(p);
@@ -279,8 +284,10 @@ rcu_dereference()
if an update happened while in the critical section, and incur
unnecessary overhead on Alpha CPUs.
+.. _back_to_1:
+
Note that the value returned by rcu_dereference() is valid
- only within the enclosing RCU read-side critical section [1].
+ only within the enclosing RCU read-side critical section |cs_1|.
For example, the following is -not- legal::
rcu_read_lock();
@@ -298,15 +305,27 @@ rcu_dereference()
it was acquired is just as illegal as doing so with normal
locking.
+.. _back_to_2:
+
As with rcu_assign_pointer(), an important function of
rcu_dereference() is to document which pointers are protected by
RCU, in particular, flagging a pointer that is subject to changing
at any time, including immediately after the rcu_dereference().
And, again like rcu_assign_pointer(), rcu_dereference() is
typically used indirectly, via the _rcu list-manipulation
- primitives, such as list_for_each_entry_rcu() [2].
+ primitives, such as list_for_each_entry_rcu() |entry_2|.
+
+.. |cs_1| raw:: html
+
+ <a href="#cs"><sup>[1]</sup></a>
+
+.. |entry_2| raw:: html
- [1] The variant rcu_dereference_protected() can be used outside
+ <a href="#entry"><sup>[2]</sup></a>
+
+.. _cs:
+
+ \ :sup:`[1]`\ The variant rcu_dereference_protected() can be used outside
of an RCU read-side critical section as long as the usage is
protected by locks acquired by the update-side code. This variant
avoids the lockdep warning that would happen when using (for
@@ -317,15 +336,18 @@ rcu_dereference()
a lockdep expression to indicate which locks must be acquired
by the caller. If the indicated protection is not provided,
a lockdep splat is emitted. See Documentation/RCU/Design/Requirements/Requirements.rst
- and the API's code comments for more details and example usage.
+ and the API's code comments for more details and example usage. :ref:`back <back_to_1>`
+
+
+.. _entry:
- [2] If the list_for_each_entry_rcu() instance might be used by
+ \ :sup:`[2]`\ If the list_for_each_entry_rcu() instance might be used by
update-side code as well as by RCU readers, then an additional
lockdep expression can be added to its list of arguments.
For example, given an additional "lock_is_held(&mylock)" argument,
the RCU lockdep code would complain only if this instance was
invoked outside of an RCU read-side critical section and without
- the protection of mylock.
+ the protection of mylock. :ref:`back <back_to_2>`
The following diagram shows how each API communicates among the
reader, updater, and reclaimer.
--
2.20.1
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next reply other threads:[~2019-11-04 13:33 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-04 13:33 Amol Grover [this message]
2019-11-04 15:03 ` [Linux-kernel-mentees] [PATCH] Documentation: RCU: whatisRCU: Fix formatting for section 2 Paul E. McKenney
2019-11-04 17:16 ` Amol Grover
2019-11-04 19:45 ` Paul E. McKenney
2019-11-05 14:52 ` Shuah Khan
2019-11-05 16:20 ` Amol Grover
2019-11-04 15:15 ` Jani Nikula
2019-11-04 17:31 ` Amol Grover
2019-11-05 6:08 ` Jani Nikula
2019-11-05 7:41 ` Amol Grover
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