diff options
| author | Will Deacon <will.deacon@arm.com> | 2013-08-12 18:04:05 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-03-06 21:30:13 -0800 |
| commit | fed783a535fe9cf3068977562235cf334fbff0b3 (patch) | |
| tree | 78055252e2992bc23f5936bb478e11e0e2f41d42 | |
| parent | f411a4439b68149518898379d7d537a32becb381 (diff) | |
ARM: 7812/1: rwlocks: retry trylock operation if strex fails on free lock
commit 00efaa0250939dc148e2d3104fb3c18395d24a2d upstream.
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>
Cc: Li Zefan <lizefan@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -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 f8b8965666e..dd64cc6f9cb 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? */ |