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[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>
This commit is contained in:
Samuel Thibault 2005-05-21 17:50:15 +02:00 committed by Linus Torvalds
parent 9636273dae
commit 10f02d1c59
2 changed files with 8 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
include/linux/spinlock.h
View File

@ -248,7 +248,7 @@ typedef struct {
#define _spin_trylock_bh(lock) ({preempt_disable(); local_bh_disable(); \
_raw_spin_trylock(lock) ? \
1 : ({preempt_enable(); local_bh_enable(); 0;});})
1 : ({preempt_enable_no_resched(); local_bh_enable(); 0;});})
#define _spin_lock(lock) \
do { \
@ -383,7 +383,7 @@ do { \
#define _spin_unlock_bh(lock) \
do { \
_raw_spin_unlock(lock); \
preempt_enable(); \
preempt_enable_no_resched(); \
local_bh_enable(); \
__release(lock); \
} while (0)
@ -391,7 +391,7 @@ do { \
#define _write_unlock_bh(lock) \
do { \
_raw_write_unlock(lock); \
preempt_enable(); \
preempt_enable_no_resched(); \
local_bh_enable(); \
__release(lock); \
} while (0)
@ -423,8 +423,8 @@ do { \
#define _read_unlock_bh(lock) \
do { \
_raw_read_unlock(lock); \
preempt_enable_no_resched(); \
local_bh_enable(); \
preempt_enable(); \
__release(lock); \
} while (0)

8
kernel/spinlock.c
View File

@ -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;
}