x86, rwsem: Stay on fast path when count > 0 in __up_write()
When count > 0 there is no need to take the call_rwsem_wake path. If we did take that path, it would just return without doing anything due to the active count not being zero. Signed-off-by: Michel Lespinasse <walken@google.com> LKML-Reference: <201007202219.o6KMJj9x021042@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>
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@ -216,9 +216,8 @@ static inline void __up_write(struct rw_semaphore *sem)
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rwsem_count_t tmp;
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rwsem_count_t tmp;
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asm volatile("# beginning __up_write\n\t"
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asm volatile("# beginning __up_write\n\t"
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LOCK_PREFIX " xadd %1,(%2)\n\t"
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LOCK_PREFIX " xadd %1,(%2)\n\t"
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/* tries to transition
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/* subtracts 0xffff0001, returns the old value */
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0xffff0001 -> 0x00000000 */
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" jns 1f\n\t"
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" jz 1f\n"
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" call call_rwsem_wake\n"
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" call call_rwsem_wake\n"
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"1:\n\t"
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"1:\n\t"
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"# ending __up_write\n"
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"# ending __up_write\n"
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