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| author | Michel Lespinasse | 2010-07-21 00:19:45 +0200 |
|---|---|---|
| committer | H. Peter Anvin | 2010-07-21 02:41:14 +0200 |
| commit | b4bcb4c28c64cc2876b4aef218d992ce806194da (patch) | |
| tree | 54ecb062c7fa2cc71f64c24a4be6d198aebf86a9 /arch | |
| parent | x86, rwsem: Stay on fast path when count > 0 in __up_write() (diff) | |
| download | kernel-qcow2-linux-b4bcb4c28c64cc2876b4aef218d992ce806194da.tar.gz kernel-qcow2-linux-b4bcb4c28c64cc2876b4aef218d992ce806194da.tar.xz kernel-qcow2-linux-b4bcb4c28c64cc2876b4aef218d992ce806194da.zip | |
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')
| -rw-r--r-- | arch/x86/include/asm/rwsem.h | 16 |
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) |