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Diffstat (limited to 'arch/arm/include/asm/spinlock.h')
-rw-r--r--arch/arm/include/asm/spinlock.h82
1 files changed, 48 insertions, 34 deletions
diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h
index 6220e9fdf4c..b07c09e5a0a 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 {
@@ -165,17 +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;
-
- __asm__ __volatile__(
-" ldrex %0, [%1]\n"
-" teq %0, #0\n"
-" strexeq %0, %2, [%1]"
- : "=&r" (tmp)
- : "r" (&rw->lock), "r" (0x80000000)
- : "cc");
-
- if (tmp == 0) {
+ unsigned long contended, res;
+
+ 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 (!contended) {
smp_mb();
return 1;
} else {
@@ -251,18 +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;
-
- __asm__ __volatile__(
-" ldrex %0, [%2]\n"
-" adds %0, %0, #1\n"
-" strexpl %1, %0, [%2]\n"
- : "=&r" (tmp), "+r" (tmp2)
- : "r" (&rw->lock)
- : "cc");
-
- smp_mb();
- return tmp2 == 0;
+ unsigned long contended, res;
+
+ 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);
+
+ /* 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? */