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authorWill Deacon <will.deacon@arm.com>2013-08-12 18:04:05 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-03-06 21:30:13 -0800
commitfed783a535fe9cf3068977562235cf334fbff0b3 (patch)
tree78055252e2992bc23f5936bb478e11e0e2f41d42
parentf411a4439b68149518898379d7d537a32becb381 (diff)
downloadlinux-linaro-stable-fed783a535fe9cf3068977562235cf334fbff0b3.tar.gz
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.h49
1 files changed, 30 insertions, 19 deletions
diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h
index f8b8965666e9..dd64cc6f9cba 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? */