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

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 0d2ab2a..56b428c 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -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);