From 2d7d253548cffdce80f4e03664686e9ccb1b0ed7 Mon Sep 17 00:00:00 2001
From: Jim Houston <jim.houston@ccur.com>
Date: Sun, 30 Jul 2006 03:03:39 -0700
Subject: [PATCH] [PATCH] fix cond_resched() fix
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 | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index 41a571806ce0..de440b220b4c 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -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();
--
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