This is a note to let you know that I've just added the patch titled
sched: Avoid double preemption in __cond_resched_*lock*()
to the 5.16-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sched-avoid-double-preemption-in-__cond_resched_-loc.patch
and it can be found in the queue-5.16 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 79ad9c6be2938ee2465df1de80d551e7c6526f38
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Sat Dec 25 01:04:57 2021 +0100
sched: Avoid double preemption in __cond_resched_*lock*()
[ Upstream commit 7e406d1ff39b8ee574036418a5043c86723170cf ]
For PREEMPT/DYNAMIC_PREEMPT the *_unlock() will already trigger a
preemption, no point in then calling preempt_schedule_common()
*again*.
Use _cond_resched() instead, since this is a NOP for the preemptible
configs while it provide a preemption point for the others.
Reported-by: xuhaifeng <xuhaifeng@xxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/YcGnvDEYBwOiV0cR@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 77563109c0ea0..d24823b3c3f9f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8176,9 +8176,7 @@ int __cond_resched_lock(spinlock_t *lock)
if (spin_needbreak(lock) || resched) {
spin_unlock(lock);
- if (resched)
- preempt_schedule_common();
- else
+ if (!_cond_resched())
cpu_relax();
ret = 1;
spin_lock(lock);
@@ -8196,9 +8194,7 @@ int __cond_resched_rwlock_read(rwlock_t *lock)
if (rwlock_needbreak(lock) || resched) {
read_unlock(lock);
- if (resched)
- preempt_schedule_common();
- else
+ if (!_cond_resched())
cpu_relax();
ret = 1;
read_lock(lock);
@@ -8216,9 +8212,7 @@ int __cond_resched_rwlock_write(rwlock_t *lock)
if (rwlock_needbreak(lock) || resched) {
write_unlock(lock);
- if (resched)
- preempt_schedule_common();
- else
+ if (!_cond_resched())
cpu_relax();
ret = 1;
write_lock(lock);
