ipc: Replace spin_unlock_wait() with lock/unlock pair

There is no agreed-upon definition of spin_unlock_wait()'s semantics,
and it appears that all callers could do just as well with a lock/unlock
pair.  This commit therefore replaces the spin_unlock_wait() call in
exit_sem() with spin_lock() followed immediately by spin_unlock().
This should be safe from a performance perspective because exit_sem()
is rarely invoked in production.

Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Alan Stern <[email protected]>
Cc: Andrea Parri <[email protected]>
Cc: Linus Torvalds <[email protected]>
Acked-by: Manfred Spraul <[email protected]>

diff --git a/ipc/sem.c b/ipc/sem.c
index 9e70cd7a17da7e74e915ce7f4061aa99aea66b89..2570830e29fcc40c3308448a7a2c4db5353dfa47 100644 (file)
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -2091,7 +2091,8 @@ void exit_sem(struct task_struct *tsk)
                         * possibility where we exit while freeary() didn't
                         * finish unlocking sem_undo_list.
                         */
-                       spin_unlock_wait(&ulp->lock);
+                       spin_lock(&ulp->lock);
+                       spin_unlock(&ulp->lock);
                        rcu_read_unlock();
                        break;
                }