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Commit 10f02d1c authored by Samuel Thibault's avatar Samuel Thibault Committed by Linus Torvalds
Browse files

[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: default avatarSamuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 9636273d

include/linux/spinlock.h

+4 −4
Original line number Diff line number Diff line
@@ -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)

kernel/spinlock.c

+4 −4
Original line number Diff line number Diff line
@@ -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;

}