3.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Will Deacon <will.deacon@xxxxxxx>
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@xxxxxxx>
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
Cc: Li Zefan <lizefan@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm/include/asm/spinlock.h | 49 ++++++++++++++++++++++++----------------
1 file changed, 30 insertions(+), 19 deletions(-)
--- 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_
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
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? */
--
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