[IA64] Fix bug in ia64 specific down() function

Chen, Kenneth W wrote:
> The memory order semantics for include/asm-ia64/semaphore.h:down()
> doesn't look right.  It is using atomic_dec_return, which eventually
> translate into ia64_fetch_and_add() that uses release semantics.
> Shouldn't it use acquire semantics?

Use ia64_fetchadd() instead of atomic_dec_return()

Acked-by: Ken Chen <kenneth.w.chen@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

diff --git a/include/asm-ia64/semaphore.h b/include/asm-ia64/semaphore.h
index bb8906285fab24104df8acf9c7f3ba1c35733ccf..f483eeb95dd1dabfd248803492bb0a6a7561b6ec 100644 (file)
--- a/include/asm-ia64/semaphore.h
+++ b/include/asm-ia64/semaphore.h
@@ -61,7 +61,7 @@ static inline void
 down (struct semaphore *sem)
 {
        might_sleep();
-       if (atomic_dec_return(&sem->count) < 0)
+       if (ia64_fetchadd(-1, &sem->count.counter, acq) < 1)
                __down(sem);
 }
 
@@ -75,7 +75,7 @@ down_interruptible (struct semaphore * sem)
        int ret = 0;
 
        might_sleep();
-       if (atomic_dec_return(&sem->count) < 0)
+       if (ia64_fetchadd(-1, &sem->count.counter, acq) < 1)
                ret = __down_interruptible(sem);
        return ret;
 }
@@ -85,7 +85,7 @@ down_trylock (struct semaphore *sem)
 {
        int ret = 0;
 
-       if (atomic_dec_return(&sem->count) < 0)
+       if (ia64_fetchadd(-1, &sem->count.counter, acq) < 1)
                ret = __down_trylock(sem);
        return ret;
 }
@@ -93,7 +93,7 @@ down_trylock (struct semaphore *sem)
 static inline void
 up (struct semaphore * sem)
 {
-       if (atomic_inc_return(&sem->count) <= 0)
+       if (ia64_fetchadd(1, &sem->count.counter, rel) <= -1)
                __up(sem);
 }