From ba0084048ab785c2cb1d6cc2cccabe642a5b799a Mon Sep 17 00:00:00 2001 From: Mark Fasheh Date: Fri, 22 Dec 2006 01:06:15 -0800 Subject: [PATCH] [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 Acked-by: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/sched.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/sched.c b/kernel/sched.c index b81ed87..850bde4 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; -- 2.7.4