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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2016-01-20 14:01:31 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2016-01-20 14:01:31 -0300
commitb4b7ff4b08e691656c9d77c758fc355833128ac0 (patch)
tree82fcb00e6b918026dc9f2d1f05ed8eee83874cc0 /include/asm-generic/rwsem.h
parent35acfa0fc609f2a2cd95cef4a6a9c3a5c38f1778 (diff)
Linux-libre 4.4-gnupck-4.4-gnu
Diffstat (limited to 'include/asm-generic/rwsem.h')
-rw-r--r--include/asm-generic/rwsem.h21
1 files changed, 14 insertions, 7 deletions
diff --git a/include/asm-generic/rwsem.h b/include/asm-generic/rwsem.h
index d48bf5a95..d6d5dc98d 100644
--- a/include/asm-generic/rwsem.h
+++ b/include/asm-generic/rwsem.h
@@ -33,7 +33,7 @@
*/
static inline void __down_read(struct rw_semaphore *sem)
{
- if (unlikely(atomic_long_inc_return((atomic_long_t *)&sem->count) <= 0))
+ if (unlikely(atomic_long_inc_return_acquire((atomic_long_t *)&sem->count) <= 0))
rwsem_down_read_failed(sem);
}
@@ -42,7 +42,7 @@ static inline int __down_read_trylock(struct rw_semaphore *sem)
long tmp;
while ((tmp = sem->count) >= 0) {
- if (tmp == cmpxchg(&sem->count, tmp,
+ if (tmp == cmpxchg_acquire(&sem->count, tmp,
tmp + RWSEM_ACTIVE_READ_BIAS)) {
return 1;
}
@@ -57,7 +57,7 @@ static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
{
long tmp;
- tmp = atomic_long_add_return(RWSEM_ACTIVE_WRITE_BIAS,
+ tmp = atomic_long_add_return_acquire(RWSEM_ACTIVE_WRITE_BIAS,
(atomic_long_t *)&sem->count);
if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
rwsem_down_write_failed(sem);
@@ -72,7 +72,7 @@ static inline int __down_write_trylock(struct rw_semaphore *sem)
{
long tmp;
- tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
+ tmp = cmpxchg_acquire(&sem->count, RWSEM_UNLOCKED_VALUE,
RWSEM_ACTIVE_WRITE_BIAS);
return tmp == RWSEM_UNLOCKED_VALUE;
}
@@ -84,7 +84,7 @@ static inline void __up_read(struct rw_semaphore *sem)
{
long tmp;
- tmp = atomic_long_dec_return((atomic_long_t *)&sem->count);
+ tmp = atomic_long_dec_return_release((atomic_long_t *)&sem->count);
if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
rwsem_wake(sem);
}
@@ -94,7 +94,7 @@ static inline void __up_read(struct rw_semaphore *sem)
*/
static inline void __up_write(struct rw_semaphore *sem)
{
- if (unlikely(atomic_long_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
+ if (unlikely(atomic_long_sub_return_release(RWSEM_ACTIVE_WRITE_BIAS,
(atomic_long_t *)&sem->count) < 0))
rwsem_wake(sem);
}
@@ -114,7 +114,14 @@ static inline void __downgrade_write(struct rw_semaphore *sem)
{
long tmp;
- tmp = atomic_long_add_return(-RWSEM_WAITING_BIAS,
+ /*
+ * When downgrading from exclusive to shared ownership,
+ * anything inside the write-locked region cannot leak
+ * into the read side. In contrast, anything in the
+ * read-locked region is ok to be re-ordered into the
+ * write side. As such, rely on RELEASE semantics.
+ */
+ tmp = atomic_long_add_return_release(-RWSEM_WAITING_BIAS,
(atomic_long_t *)&sem->count);
if (tmp < 0)
rwsem_downgrade_wake(sem);