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author | Ingo Molnar <mingo@elte.hu> | 2006-12-30 03:48:13 +0300 |
---|---|---|
committer | Linus Torvalds <torvalds@woody.osdl.org> | 2006-12-30 21:56:41 +0300 |
commit | 9414232fa0cc28e2f51b8c76d260f2748f7953fc (patch) | |
tree | 71717c2907f4fe2f50aba355e8cf03f3a2a8b385 | |
parent | d449db98d5d7d90f29f9f6e091b0e1d996184df1 (diff) | |
download | linux-9414232fa0cc28e2f51b8c76d260f2748f7953fc.tar.xz |
[PATCH] sched: fix cond_resched_softirq() offset
Remove the __resched_legal() check: it is conceptually broken. The biggest
problem it had is that it can mask buggy cond_resched() calls. A
cond_resched() call is only legal if we are not in an atomic context, with
two narrow exceptions:
- if the system is booting
- a reacquire_kernel_lock() down() done while PREEMPT_ACTIVE is set
But __resched_legal() hid this and just silently returned whenever
these primitives were called from invalid contexts. (Same goes for
cond_resched_locked() and cond_resched_softirq()).
Furthermore, the __legal_resched(0) call was buggy in that it caused
unnecessarily long softirq latencies via cond_resched_softirq(). (which is
only called from softirq-off sections, hence the code did nothing.)
The fix is to resurrect the efficiency of the might_sleep checks and to
only allow the narrow exceptions.
Signed-off-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 | 18 |
1 files changed, 4 insertions, 14 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index b515e3caad7f..3df33da0dafc 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -4617,17 +4617,6 @@ asmlinkage long sys_sched_yield(void) return 0; } -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; -} - static void __cond_resched(void) { #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP @@ -4647,7 +4636,8 @@ static void __cond_resched(void) int __sched cond_resched(void) { - if (need_resched() && __resched_legal(0)) { + if (need_resched() && !(preempt_count() & PREEMPT_ACTIVE) && + system_state == SYSTEM_RUNNING) { __cond_resched(); return 1; } @@ -4673,7 +4663,7 @@ int cond_resched_lock(spinlock_t *lock) ret = 1; spin_lock(lock); } - if (need_resched() && __resched_legal(1)) { + if (need_resched() && system_state == SYSTEM_RUNNING) { spin_release(&lock->dep_map, 1, _THIS_IP_); _raw_spin_unlock(lock); preempt_enable_no_resched(); @@ -4689,7 +4679,7 @@ int __sched cond_resched_softirq(void) { BUG_ON(!in_softirq()); - if (need_resched() && __resched_legal(0)) { + if (need_resched() && system_state == SYSTEM_RUNNING) { raw_local_irq_disable(); _local_bh_enable(); raw_local_irq_enable(); |