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authorWill Deacon <will.deacon@arm.com>2013-06-05 11:27:26 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-03-06 21:30:13 -0800
commitf411a4439b68149518898379d7d537a32becb381 (patch)
treefd18a509b56ea9c40e1655956757492c6b017126
parent79e43826099dad17a9ff6014b508f2de950099f6 (diff)
downloadlinux-linaro-stable-f411a4439b68149518898379d7d537a32becb381.tar.gz
ARM: 7749/1: spinlock: retry trylock operation if strex fails on free lock
commit 15e7e5c1ebf556cd620c9b091e121091ac760f6d upstream. An exclusive store instruction may fail for reasons other than lock contention (e.g. a cache eviction during the critical section) so, in line with other architectures using similar exclusive instructions (alpha, mips, powerpc), retry the trylock operation if the lock appears to be free but the strex reported failure. Reported-by: Tony Thompson <anthony.thompson@arm.com> 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.h25
1 files changed, 14 insertions, 11 deletions
diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h
index 6220e9fdf4c7..f8b8965666e9 100644
--- a/arch/arm/include/asm/spinlock.h
+++ b/arch/arm/include/asm/spinlock.h
@@ -97,19 +97,22 @@ static inline void arch_spin_lock(arch_spinlock_t *lock)
static inline int arch_spin_trylock(arch_spinlock_t *lock)
{
- unsigned long tmp;
+ unsigned long contended, res;
u32 slock;
- __asm__ __volatile__(
-" ldrex %0, [%2]\n"
-" subs %1, %0, %0, ror #16\n"
-" addeq %0, %0, %3\n"
-" strexeq %1, %0, [%2]"
- : "=&r" (slock), "=&r" (tmp)
- : "r" (&lock->slock), "I" (1 << TICKET_SHIFT)
- : "cc");
-
- if (tmp == 0) {
+ do {
+ __asm__ __volatile__(
+ " ldrex %0, [%3]\n"
+ " mov %2, #0\n"
+ " subs %1, %0, %0, ror #16\n"
+ " addeq %0, %0, %4\n"
+ " strexeq %2, %0, [%3]"
+ : "=&r" (slock), "=&r" (contended), "=r" (res)
+ : "r" (&lock->slock), "I" (1 << TICKET_SHIFT)
+ : "cc");
+ } while (res);
+
+ if (!contended) {
smp_mb();
return 1;
} else {