[PATCH] spin_unlock_bh() and preempt_check_resched()

In _spin_unlock_bh(lock):
	do { \
		_raw_spin_unlock(lock); \
		preempt_enable(); \
		local_bh_enable(); \
		__release(lock); \
	} while (0)

there is no reason for using preempt_enable() instead of a simple
preempt_enable_no_resched()

Since we know bottom halves are disabled, preempt_schedule() will always
return at once (preempt_count!=0), and hence preempt_check_resched() is
useless here...

This fixes it by using "preempt_enable_no_resched()" instead of the
"preempt_enable()", and thus avoids the useless preempt_check_resched()
just before re-enabling bottom halves.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/kernel/spinlock.c b/kernel/spinlock.c
index e15ed17..0c3f9d8 100644
--- a/kernel/spinlock.c
+++ b/kernel/spinlock.c
@@ -294,7 +294,7 @@ EXPORT_SYMBOL(_spin_unlock_irq);
 void __lockfunc _spin_unlock_bh(spinlock_t *lock)
 {
 	_raw_spin_unlock(lock);
-	preempt_enable();
+	preempt_enable_no_resched();
 	local_bh_enable();
 }
 EXPORT_SYMBOL(_spin_unlock_bh);
@@ -318,7 +318,7 @@ EXPORT_SYMBOL(_read_unlock_irq);
 void __lockfunc _read_unlock_bh(rwlock_t *lock)
 {
 	_raw_read_unlock(lock);
-	preempt_enable();
+	preempt_enable_no_resched();
 	local_bh_enable();
 }
 EXPORT_SYMBOL(_read_unlock_bh);
@@ -342,7 +342,7 @@ EXPORT_SYMBOL(_write_unlock_irq);
 void __lockfunc _write_unlock_bh(rwlock_t *lock)
 {
 	_raw_write_unlock(lock);
-	preempt_enable();
+	preempt_enable_no_resched();
 	local_bh_enable();
 }
 EXPORT_SYMBOL(_write_unlock_bh);
@@ -354,7 +354,7 @@ int __lockfunc _spin_trylock_bh(spinlock_t *lock)
 	if (_raw_spin_trylock(lock))
 		return 1;
 
-	preempt_enable();
+	preempt_enable_no_resched();
 	local_bh_enable();
 	return 0;
 }