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sched: Avoid double preemption in __cond_resched_*lock*()
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
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1 changed files with 3 additions and 9 deletions
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@ -8218,9 +8218,7 @@ int __cond_resched_lock(spinlock_t *lock)
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if (spin_needbreak(lock) || resched) {
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spin_unlock(lock);
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if (resched)
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preempt_schedule_common();
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else
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if (!_cond_resched())
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cpu_relax();
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ret = 1;
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spin_lock(lock);
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@ -8238,9 +8236,7 @@ int __cond_resched_rwlock_read(rwlock_t *lock)
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if (rwlock_needbreak(lock) || resched) {
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read_unlock(lock);
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if (resched)
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preempt_schedule_common();
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else
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if (!_cond_resched())
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cpu_relax();
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ret = 1;
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read_lock(lock);
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@ -8258,9 +8254,7 @@ int __cond_resched_rwlock_write(rwlock_t *lock)
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if (rwlock_needbreak(lock) || resched) {
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write_unlock(lock);
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if (resched)
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preempt_schedule_common();
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else
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if (!_cond_resched())
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cpu_relax();
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ret = 1;
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write_lock(lock);
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