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Commit 2d7d2535 authored by Jim Houston's avatar Jim Houston Committed by Linus Torvalds
Browse files

[PATCH] fix cond_resched() fix 



In cond_resched_lock() it calls __resched_legal() before dropping the spin
lock.  __resched_legal() will always finds the preempt_count non-zero and
will prevent the call to __cond_resched().

The attached patch adds a parameter to __resched_legal() with the expected
preempt_count value.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: <stable@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 6ea24f9a

kernel/sched.c

+5 −5
Original line number Diff line number Diff line
@@ -4456,9 +4456,9 @@ asmlinkage long sys_sched_yield(void) 
	return 0;

}



static inline int __resched_legal(void)

static inline int __resched_legal(int expected_preempt_count)

{

	if (unlikely(preempt_count()))

	if (unlikely(preempt_count() != expected_preempt_count))

		return 0;

	if (unlikely(system_state != SYSTEM_RUNNING))

		return 0;
@@ -4484,7 +4484,7 @@ static void __cond_resched(void) 


int __sched cond_resched(void)

{

	if (need_resched() && __resched_legal()) {

	if (need_resched() && __resched_legal(0)) {

		__cond_resched();

		return 1;

	}
@@ -4510,7 +4510,7 @@ int cond_resched_lock(spinlock_t *lock) 
		ret = 1;

		spin_lock(lock);

	}

	if (need_resched() && __resched_legal()) {

	if (need_resched() && __resched_legal(1)) {

		spin_release(&lock->dep_map, 1, _THIS_IP_);

		_raw_spin_unlock(lock);

		preempt_enable_no_resched();
@@ -4526,7 +4526,7 @@ int __sched cond_resched_softirq(void) 
{

	BUG_ON(!in_softirq());



	if (need_resched() && __resched_legal()) {

	if (need_resched() && __resched_legal(0)) {

		raw_local_irq_disable();

		_local_bh_enable();

		raw_local_irq_enable();