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x86, rwsem: Minor cleanups 

Clarified few comments and made initialization of %edx/%rdx more uniform
accross __down_write_nested, __up_read and __up_write functions.

Signed-off-by: Michel Lespinasse <walken@google.com>
LKML-Reference: <201007202219.o6KMJkiA021048@imap1.linux-foundation.org>
Acked-by: David Howells <dhowells@redhat.com>
Cc: Mike Waychison <mikew@google.com>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: Ying Han <yinghan@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Michel Lespinasse 2010-07-20 15:19:45 -07:00 committed by H. Peter Anvin
parent a751bd858b
commit b4bcb4c28c
1 changed files with 7 additions and 9 deletions
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16
arch/x86/include/asm/rwsem.h
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@ -118,7 +118,7 @@ static inline void __down_read(struct rw_semaphore *sem)
{
asm volatile("# beginning down_read\n\t"
LOCK_PREFIX _ASM_INC "(%1)\n\t"
/* adds 0x00000001, returns the old value */
/* adds 0x00000001 */
" jns 1f\n"
" call call_rwsem_down_read_failed\n"
"1:\n\t"
@ -156,11 +156,9 @@ static inline int __down_read_trylock(struct rw_semaphore *sem)
static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
{
rwsem_count_t tmp;
tmp = RWSEM_ACTIVE_WRITE_BIAS;
asm volatile("# beginning down_write\n\t"
LOCK_PREFIX " xadd %1,(%2)\n\t"
/* subtract 0x0000ffff, returns the old value */
/* adds 0xffff0001, returns the old value */
" test %1,%1\n\t"
/* was the count 0 before? */
" jz 1f\n"
@ -168,7 +166,7 @@ static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
"1:\n"
"# ending down_write"
: "+m" (sem->count), "=d" (tmp)
: "a" (sem), "1" (tmp)
: "a" (sem), "1" (RWSEM_ACTIVE_WRITE_BIAS)
: "memory", "cc");
}
@ -195,16 +193,16 @@ static inline int __down_write_trylock(struct rw_semaphore *sem)
*/
static inline void __up_read(struct rw_semaphore *sem)
{
rwsem_count_t tmp = -RWSEM_ACTIVE_READ_BIAS;
rwsem_count_t tmp;
asm volatile("# beginning __up_read\n\t"
LOCK_PREFIX " xadd %1,(%2)\n\t"
/* subtracts 1, returns the old value */
" jns 1f\n\t"
" call call_rwsem_wake\n"
" call call_rwsem_wake\n" /* expects old value in %edx */
"1:\n"
"# ending __up_read\n"
: "+m" (sem->count), "=d" (tmp)
: "a" (sem), "1" (tmp)
: "a" (sem), "1" (-RWSEM_ACTIVE_READ_BIAS)
: "memory", "cc");
}
@ -218,7 +216,7 @@ static inline void __up_write(struct rw_semaphore *sem)
LOCK_PREFIX " xadd %1,(%2)\n\t"
/* subtracts 0xffff0001, returns the old value */
" jns 1f\n\t"
" call call_rwsem_wake\n"
" call call_rwsem_wake\n" /* expects old value in %edx */
"1:\n\t"
"# ending __up_write\n"
: "+m" (sem->count), "=d" (tmp)