ipc/sem: simplify wait-wake loop

Instead of using the reverse goto, we can simplify the flow and make it
more language natural by just doing do-while instead.  One would hope
this is the standard way (or obviously just with a while bucle) that we
do wait/wakeup handling in the kernel.  The exact same logic is kept,
just more indented.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/1478708774-28826-2-git-send-email-dave@stgolabs.netSigned-off-by: NDavidlohr Bueso <dbueso@suse.de>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

ipc/sem.c

@@ -1963,7 +1963,7 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
 		sma->complex_count++;
 	}
 
-sleep_again:
+	do {
 		queue.status = -EINTR;
 		queue.sleeper = current;
 
@@ -1977,22 +1977,23 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
 			schedule();
 
 		/*
-	 * fastpath: the semop has completed, either successfully or not, from
-	 * the syscall pov, is quite irrelevant to us at this point; we're done.
+		 * fastpath: the semop has completed, either successfully or
+		 * not, from the syscall pov, is quite irrelevant to us at this
+		 * point; we're done.
 		 *
 		 * We _do_ care, nonetheless, about being awoken by a signal or
-	 * spuriously.  The queue.status is checked again in the slowpath (aka
-	 * after taking sem_lock), such that we can detect scenarios where we
-	 * were awakened externally, during the window between wake_q_add() and
-	 * wake_up_q().
+		 * spuriously.  The queue.status is checked again in the
+		 * slowpath (aka after taking sem_lock), such that we can detect
+		 * scenarios where we were awakened externally, during the
+		 * window between wake_q_add() and wake_up_q().
 		 */
 		error = READ_ONCE(queue.status);
 		if (error != -EINTR) {
 			/*
-		 * User space could assume that semop() is a memory barrier:
-		 * Without the mb(), the cpu could speculatively read in user
-		 * space stale data that was overwritten by the previous owner
-		 * of the semaphore.
+			 * User space could assume that semop() is a memory
+			 * barrier: Without the mb(), the cpu could
+			 * speculatively read in userspace stale data that was
+			 * overwritten by the previous owner of the semaphore.
 			 */
 			smp_mb();
 			goto out_free;
@@ -2022,12 +2023,7 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
 		 */
 		if (timeout && jiffies_left == 0)
 			error = -EAGAIN;
-
-	/*
-	 * If the wakeup was spurious, just retry.
-	 */
-	if (error == -EINTR && !signal_pending(current))
-		goto sleep_again;
+	} while (error == -EINTR && !signal_pending(current)); /* spurious */
 
 	unlink_queue(sma, &queue);