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authorIngo Molnar <mingo@elte.hu>2006-12-29 16:48:13 -0800
committerLinus Torvalds <torvalds@woody.osdl.org>2006-12-30 10:56:41 -0800
commit9414232fa0cc28e2f51b8c76d260f2748f7953fc (patch)
tree71717c2907f4fe2f50aba355e8cf03f3a2a8b385
parentd449db98d5d7d90f29f9f6e091b0e1d996184df1 (diff)
downloadop-kernel-dev-9414232fa0cc28e2f51b8c76d260f2748f7953fc.zip
op-kernel-dev-9414232fa0cc28e2f51b8c76d260f2748f7953fc.tar.gz
[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.c18
1 files changed, 4 insertions, 14 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index b515e3c..3df33da 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();
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