From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
fweisbec@gmail.com, oleg@redhat.com,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 09/10] doc: Eliminate cond_resched_rcu_qs() in favor of cond_resched()
Date: Fri, 1 Dec 2017 11:21:43 -0800 [thread overview]
Message-ID: <1512156104-20104-9-git-send-email-paulmck@linux.vnet.ibm.com> (raw)
In-Reply-To: <20171201192122.GA19301@linux.vnet.ibm.com>
Now that cond_resched() also provides RCU quiescent states when
needed, it can be used in place of cond_resched_rcu_qs(). This
commit therefore documents this change.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
Documentation/RCU/Design/Data-Structures/Data-Structures.html | 3 ++-
Documentation/RCU/Design/Requirements/Requirements.html | 4 ++--
Documentation/RCU/stallwarn.txt | 10 ++++------
3 files changed, 8 insertions(+), 9 deletions(-)
diff --git a/Documentation/RCU/Design/Data-Structures/Data-Structures.html b/Documentation/RCU/Design/Data-Structures/Data-Structures.html
index 38d6d800761f..412466e4967a 100644
--- a/Documentation/RCU/Design/Data-Structures/Data-Structures.html
+++ b/Documentation/RCU/Design/Data-Structures/Data-Structures.html
@@ -1097,7 +1097,8 @@ will cause the CPU to disregard the values of its counters on
its next exit from idle.
Finally, the <tt>rcu_qs_ctr_snap</tt> field is used to detect
cases where a given operation has resulted in a quiescent state
-for all flavors of RCU, for example, <tt>cond_resched_rcu_qs()</tt>.
+for all flavors of RCU, for example, <tt>cond_resched()</tt>
+when RCU has indicated a need for quiescent states.
<h5>RCU Callback Handling</h5>
diff --git a/Documentation/RCU/Design/Requirements/Requirements.html b/Documentation/RCU/Design/Requirements/Requirements.html
index 62e847bcdcdd..0372e6c54eef 100644
--- a/Documentation/RCU/Design/Requirements/Requirements.html
+++ b/Documentation/RCU/Design/Requirements/Requirements.html
@@ -2797,7 +2797,7 @@ RCU must avoid degrading real-time response for CPU-bound threads, whether
executing in usermode (which is one use case for
<tt>CONFIG_NO_HZ_FULL=y</tt>) or in the kernel.
That said, CPU-bound loops in the kernel must execute
-<tt>cond_resched_rcu_qs()</tt> at least once per few tens of milliseconds
+<tt>cond_resched()</tt> at least once per few tens of milliseconds
in order to avoid receiving an IPI from RCU.
<p>
@@ -3128,7 +3128,7 @@ The solution, in the form of
is to have implicit
read-side critical sections that are delimited by voluntary context
switches, that is, calls to <tt>schedule()</tt>,
-<tt>cond_resched_rcu_qs()</tt>, and
+<tt>cond_resched()</tt>, and
<tt>synchronize_rcu_tasks()</tt>.
In addition, transitions to and from userspace execution also delimit
tasks-RCU read-side critical sections.
diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt
index a08f928c8557..4259f95c3261 100644
--- a/Documentation/RCU/stallwarn.txt
+++ b/Documentation/RCU/stallwarn.txt
@@ -23,12 +23,10 @@ o A CPU looping with preemption disabled. This condition can
o A CPU looping with bottom halves disabled. This condition can
result in RCU-sched and RCU-bh stalls.
-o For !CONFIG_PREEMPT kernels, a CPU looping anywhere in the
- kernel without invoking schedule(). Note that cond_resched()
- does not necessarily prevent RCU CPU stall warnings. Therefore,
- if the looping in the kernel is really expected and desirable
- behavior, you might need to replace some of the cond_resched()
- calls with calls to cond_resched_rcu_qs().
+o For !CONFIG_PREEMPT kernels, a CPU looping anywhere in the kernel
+ without invoking schedule(). If the looping in the kernel is
+ really expected and desirable behavior, you might need to add
+ some calls to cond_resched().
o Booting Linux using a console connection that is too slow to
keep up with the boot-time console-message rate. For example,
--
2.5.2
next prev parent reply other threads:[~2017-12-01 19:21 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-01 19:21 [PATCH tip/core/rcu 0/10] Don not IPI offline CPUs, de-emphasize cond_resched_rcu_qs() Paul E. McKenney
2017-12-01 19:21 ` [PATCH tip/core/rcu 01/10] sched: Stop resched_cpu() from sending IPIs to offline CPUs Paul E. McKenney
2017-12-01 19:21 ` [PATCH tip/core/rcu 02/10] sched: Stop switched_to_rt() " Paul E. McKenney
2017-12-01 19:21 ` [PATCH tip/core/rcu 03/10] netfilter: Eliminate cond_resched_rcu_qs() in favor of cond_resched() Paul E. McKenney
2017-12-01 19:21 ` [PATCH tip/core/rcu 04/10] mm: " Paul E. McKenney
2017-12-01 19:21 ` [PATCH tip/core/rcu 05/10] workqueue: " Paul E. McKenney
2017-12-02 1:06 ` Lai Jiangshan
2017-12-04 18:28 ` Paul E. McKenney
2017-12-01 19:21 ` [PATCH tip/core/rcu 06/10] trace: " Paul E. McKenney
2018-02-24 20:12 ` Steven Rostedt
2018-02-25 17:49 ` Paul E. McKenney
2018-02-25 18:17 ` Paul E. McKenney
2018-02-25 18:39 ` Paul E. McKenney
2018-02-27 2:29 ` Steven Rostedt
2018-02-27 15:36 ` Paul E. McKenney
2018-02-28 23:12 ` Steven Rostedt
2018-03-01 1:21 ` Paul E. McKenney
2018-03-01 5:04 ` Steven Rostedt
2018-03-01 20:48 ` Paul E. McKenney
2018-03-02 20:06 ` Steven Rostedt
2018-03-03 0:54 ` Paul E. McKenney
2018-02-26 4:57 ` Steven Rostedt
2018-02-26 5:47 ` Paul E. McKenney
2017-12-01 19:21 ` [PATCH tip/core/rcu 07/10] softirq: " Paul E. McKenney
2017-12-01 19:21 ` [PATCH tip/core/rcu 08/10] fs: " Paul E. McKenney
2017-12-01 19:21 ` Paul E. McKenney [this message]
2017-12-01 19:21 ` [PATCH tip/core/rcu 10/10] rcu: Account for rcu_all_qs() in cond_resched() Paul E. McKenney
2017-12-02 8:56 ` Peter Zijlstra
2017-12-02 12:22 ` Paul E. McKenney
2017-12-02 13:55 ` Peter Zijlstra
2018-02-24 20:18 ` Steven Rostedt
2018-02-25 17:52 ` Paul E. McKenney
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