[PATCH 3/7] ipc/sem.c: Rely on spin_unlock_wait() = spin_lock();spin_unlock().

[Manfred Spraul]

>From memory ordering point of view, spin_unlock_wait() provides
the same guarantees as spin_lock(); spin_unlock().

Therefore the smp_mb() after spin_lock() is not necessary,
spin_unlock_wait() must provide the memory ordering.

Signed-off-by: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
---
 ipc/sem.c | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/ipc/sem.c b/ipc/sem.c
index 6586e0a..a5da82c 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -355,14 +355,6 @@ static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
 		 */
 		spin_lock(&sem->lock);
 
-		/*
-		 * See 51d7d5205d33
-		 * ("powerpc: Add smp_mb() to arch_spin_is_locked()"):
-		 * A full barrier is required: the write of sem->lock
-		 * must be visible before the read is executed
-		 */
-		smp_mb();
-
 		if (!smp_load_acquire(&sma->complex_mode)) {
 			/* fast path successful! */
 			return sops->sem_num;
-- 
2.7.4