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| author | Mark Fasheh <mark.fasheh@oracle.com> | 2006-12-22 01:06:15 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.osdl.org> | 2006-12-22 08:55:46 -0800 |
| commit | ba0084048ab785c2cb1d6cc2cccabe642a5b799a (patch) | |
| tree | 402f1d6a726413a734ab05415a8f3277d23310e7 | |
| parent | 2aea4fb61609ba7ef82f7dc6fca116bda88816e1 (diff) | |
| download | lwn-ba0084048ab785c2cb1d6cc2cccabe642a5b799a.tar.gz lwn-ba0084048ab785c2cb1d6cc2cccabe642a5b799a.zip | |
[PATCH] Conditionally check expected_preempt_count in __resched_legal()
Commit 2d7d253548cffdce80f4e03664686e9ccb1b0ed7 ("fix cond_resched() fix")
introduced an 'expected_preempt_count' parameter to __resched_legal() to
fix a bug where it was returning a false negative when called from
cond_resched_lock() and preemption was enabled.
Unfortunately this broke things for when preemption is disabled.
preempt_count() will always return zero, thus failing the check against any
value of expected_preempt_count not equal to zero. cond_resched_lock() for
example, passes an expected_preempt_count value of 1.
So fix the fix for the cond_resched() fix by skipping the check of
preempt_count() against expected_preempt_count when preemption is disabled.
Credit should go to Sunil Mushran for spotting the bug during testing.
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
| -rw-r--r-- | kernel/sched.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index b81ed8703f70..850bde4b31a2 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -4619,8 +4619,10 @@ asmlinkage long sys_sched_yield(void) static inline int __resched_legal(int expected_preempt_count) { +#ifdef CONFIG_PREEMPT if (unlikely(preempt_count() != expected_preempt_count)) return 0; +#endif if (unlikely(system_state != SYSTEM_RUNNING)) return 0; return 1; |