[PATCH] fix cond_resched() fix
authorJim Houston <jim.houston@ccur.com>
Sun, 30 Jul 2006 10:03:39 +0000 (03:03 -0700)
committerLinus Torvalds <torvalds@g5.osdl.org>
Mon, 31 Jul 2006 20:28:40 +0000 (13:28 -0700)
In cond_resched_lock() it calls __resched_legal() before dropping the spin
lock.  __resched_legal() will always finds the preempt_count non-zero and
will prevent the call to __cond_resched().

The attached patch adds a parameter to __resched_legal() with the expected
preempt_count value.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
kernel/sched.c

index 41a571806ce04b877451c768bc47e71bc6cbd5ab..de440b220b4cb711c6ee1c54e2faa32b9c1737d8 100644 (file)
@@ -4456,9 +4456,9 @@ asmlinkage long sys_sched_yield(void)
        return 0;
 }
 
-static inline int __resched_legal(void)
+static inline int __resched_legal(int expected_preempt_count)
 {
-       if (unlikely(preempt_count()))
+       if (unlikely(preempt_count() != expected_preempt_count))
                return 0;
        if (unlikely(system_state != SYSTEM_RUNNING))
                return 0;
@@ -4484,7 +4484,7 @@ static void __cond_resched(void)
 
 int __sched cond_resched(void)
 {
-       if (need_resched() && __resched_legal()) {
+       if (need_resched() && __resched_legal(0)) {
                __cond_resched();
                return 1;
        }
@@ -4510,7 +4510,7 @@ int cond_resched_lock(spinlock_t *lock)
                ret = 1;
                spin_lock(lock);
        }
-       if (need_resched() && __resched_legal()) {
+       if (need_resched() && __resched_legal(1)) {
                spin_release(&lock->dep_map, 1, _THIS_IP_);
                _raw_spin_unlock(lock);
                preempt_enable_no_resched();
@@ -4526,7 +4526,7 @@ int __sched cond_resched_softirq(void)
 {
        BUG_ON(!in_softirq());
 
-       if (need_resched() && __resched_legal()) {
+       if (need_resched() && __resched_legal(0)) {
                raw_local_irq_disable();
                _local_bh_enable();
                raw_local_irq_enable();