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authorIngo Molnar <mingo@elte.hu>2006-12-29 16:48:13 -0800
committerChris Wright <chrisw@sous-sol.org>2007-02-05 08:31:45 -0800
commit9868646d7a415771f015620ee40edfe257dc27d3 (patch)
tree18f67d6d33aeb6bfaf6630677803e1f40ff19882
parent56cf77091500709c99253b305708bc47196f7d21 (diff)
[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> [chrisw: backport to 2.6.19.2] Signed-off-by: Chris Wright <chrisw@sous-sol.org>
-rw-r--r--kernel/sched.c16
1 files changed, 4 insertions, 12 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 5f6939cad314..ee200b2ac8dc 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4524,15 +4524,6 @@ asmlinkage long sys_sched_yield(void)
return 0;
}
-static inline int __resched_legal(int expected_preempt_count)
-{
- if (unlikely(preempt_count() != expected_preempt_count))
- return 0;
- if (unlikely(system_state != SYSTEM_RUNNING))
- return 0;
- return 1;
-}
-
static void __cond_resched(void)
{
#ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
@@ -4552,7 +4543,8 @@ 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;
}
@@ -4578,7 +4570,7 @@ 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();
@@ -4594,7 +4586,7 @@ 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();