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authorMichel Lespinasse <walken@google.com>2010-07-20 15:19:45 -0700
committerH. Peter Anvin <hpa@linux.intel.com>2010-07-20 17:41:14 -0700
commitb4bcb4c28c64cc2876b4aef218d992ce806194da (patch)
tree54ecb062c7fa2cc71f64c24a4be6d198aebf86a9 /arch/x86/include/asm/rwsem.h
parenta751bd858b16dce57f3b6b85ba07946df1bd7be4 (diff)
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>
Diffstat (limited to 'arch/x86/include/asm/rwsem.h')
-rw-r--r--arch/x86/include/asm/rwsem.h16
1 files changed, 7 insertions, 9 deletions
diff --git a/arch/x86/include/asm/rwsem.h b/arch/x86/include/asm/rwsem.h
index 5bf5e04e497f..d1e41b0f9b60 100644
--- a/arch/x86/include/asm/rwsem.h
+++ b/arch/x86/include/asm/rwsem.h
@@ -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)