diff options
| author | Ingo Molnar <mingo@elte.hu> | 2006-12-29 16:48:13 -0800 |
|---|---|---|
| committer | Chris Wright <chrisw@sous-sol.org> | 2007-02-05 08:31:45 -0800 |
| commit | 9868646d7a415771f015620ee40edfe257dc27d3 (patch) | |
| tree | 18f67d6d33aeb6bfaf6630677803e1f40ff19882 /kernel/sched.c | |
| parent | 56cf77091500709c99253b305708bc47196f7d21 (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>
Diffstat (limited to 'kernel/sched.c')
| -rw-r--r-- | kernel/sched.c | 16 |
1 files changed, 4 insertions, 12 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index 5f6939cad31..ee200b2ac8d 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(); |