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sched: Avoid double preemption in __cond_resched_*lock*()

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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@oppo.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/YcGnvDEYBwOiV0cR@hirez.programming.kicks-ass.net
This commit is contained in:
Peter Zijlstra 2021-12-25 01:04:57 +01:00
parent a315da5e68
commit 7e406d1ff3
1 changed files with 3 additions and 9 deletions
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12
kernel/sched/core.c
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@ -8218,9 +8218,7 @@ 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);
@ -8238,9 +8236,7 @@ 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);
@ -8258,9 +8254,7 @@ 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);