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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>
hifive-unleashed-5.1
Michel Lespinasse 2010-07-20 15:19:45 -07:00 committed by H. Peter Anvin
parent e0959371b4
commit a751bd858b
1 changed files with 2 additions and 3 deletions
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5
arch/x86/include/asm/rwsem.h
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@ -216,9 +216,8 @@ static inline void __up_write(struct rw_semaphore *sem)
rwsem_count_t tmp;
asm volatile("# beginning __up_write\n\t"
LOCK_PREFIX " xadd %1,(%2)\n\t"
/* tries to transition
0xffff0001 -> 0x00000000 */
" jz 1f\n"
/* subtracts 0xffff0001, returns the old value */
" jns 1f\n\t"
" call call_rwsem_wake\n"
"1:\n\t"
"# ending __up_write\n"