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[ARM] Fix ARM __raw_read_trylock() implementation 

Matthew Wilcox pointed out that the generic implementation
of this is unfit for use.  Here's an ARM optimised version
instead.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King 2006-08-31 15:09:30 +01:00 committed by Russell King
parent 0355b3e039
commit 8e34703b93
1 changed files with 15 additions and 1 deletions
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16
include/asm-arm/spinlock.h
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@ -199,7 +199,21 @@ static inline void __raw_read_unlock(raw_rwlock_t *rw)
: "cc");
}
#define __raw_read_trylock(lock) generic__raw_read_trylock(lock)
static inline int __raw_read_trylock(raw_rwlock_t *rw)
{
unsigned long tmp tmp2 = 1;
__asm__ __volatile__(
"1: ldrex %0, [%2]\n"
" adds %0, %0, #1\n"
" strexpl %1, %0, [%2]\n"
: "=&r" (tmp), "+r" (tmp2)
: "r" (&rw->lock)
: "cc");
smp_mb();
return tmp2 == 0;
}
/* read_can_lock - would read_trylock() succeed? */
#define __raw_read_can_lock(x) ((x)->lock < 0x80000000)