diff options
| author | Will Deacon <will.deacon@arm.com> | 2013-08-12 18:04:05 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2013-08-13 20:22:44 +0100 |
| commit | 00efaa0250939dc148e2d3104fb3c18395d24a2d (patch) | |
| tree | 2d3f9322f15171499a6b579a1a06d6497dc5ba08 | |
| parent | afa31d8eb86fc2f25083e675d57ac8173a98f999 (diff) | |
ARM: 7812/1: rwlocks: retry trylock operation if strex fails on free lock
Commit 15e7e5c1ebf5 ("ARM: 7749/1: spinlock: retry trylock operation if
strex fails on free lock") modifying our arch_spin_trylock to retry the
acquisition if the lock appeared uncontended, but the strex failed.
This patch does the same for rwlocks, which were missed by the original
patch.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
| -rw-r--r-- | arch/arm/include/asm/spinlock.h | 49 |
1 files changed, 30 insertions, 19 deletions
diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h index 7ed43f68e04..b07c09e5a0a 100644 --- a/arch/arm/include/asm/spinlock.h +++ b/arch/arm/include/asm/spinlock.h @@ -168,17 +168,20 @@ static inline void arch_write_lock(arch_rwlock_t *rw) static inline int arch_write_trylock(arch_rwlock_t *rw) { - unsigned long tmp; + unsigned long contended, res; - __asm__ __volatile__( -" ldrex %0, [%1]\n" -" teq %0, #0\n" -" strexeq %0, %2, [%1]" - : "=&r" (tmp) - : "r" (&rw->lock), "r" (0x80000000) - : "cc"); + do { + __asm__ __volatile__( + " ldrex %0, [%2]\n" + " mov %1, #0\n" + " teq %0, #0\n" + " strexeq %1, %3, [%2]" + : "=&r" (contended), "=&r" (res) + : "r" (&rw->lock), "r" (0x80000000) + : "cc"); + } while (res); - if (tmp == 0) { + if (!contended) { smp_mb(); return 1; } else { @@ -254,18 +257,26 @@ static inline void arch_read_unlock(arch_rwlock_t *rw) static inline int arch_read_trylock(arch_rwlock_t *rw) { - unsigned long tmp, tmp2 = 1; + unsigned long contended, res; - __asm__ __volatile__( -" ldrex %0, [%2]\n" -" adds %0, %0, #1\n" -" strexpl %1, %0, [%2]\n" - : "=&r" (tmp), "+r" (tmp2) - : "r" (&rw->lock) - : "cc"); + do { + __asm__ __volatile__( + " ldrex %0, [%2]\n" + " mov %1, #0\n" + " adds %0, %0, #1\n" + " strexpl %1, %0, [%2]" + : "=&r" (contended), "=&r" (res) + : "r" (&rw->lock) + : "cc"); + } while (res); - smp_mb(); - return tmp2 == 0; + /* If the lock is negative, then it is already held for write. */ + if (contended < 0x80000000) { + smp_mb(); + return 1; + } else { + return 0; + } } /* read_can_lock - would read_trylock() succeed? */ |