---

yaml
---
r: 176696
b: refs/heads/master
c: d987f8b
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 636c6be823870d829b37fc96655bb8820a6a9be9
+refs/heads/master: d987f8b213f2cdcc52b2ca9ee67161516e4d256a

trunk/ipc/sem.c

@@ -474,6 +474,17 @@ static void update_queue(struct sem_array *sma, int semnum)
 		q = (struct sem_queue *)((char *)walk - offset);
 		walk = walk->next;
 
+		/* If we are scanning the single sop, per-semaphore list of
+		 * one semaphore and that semaphore is 0, then it is not
+		 * necessary to scan the "alter" entries: simple increments
+		 * that affect only one entry succeed immediately and cannot
+		 * be in the  per semaphore pending queue, and decrements
+		 * cannot be successful if the value is already 0.
+		 */
+		if (semnum != -1 && sma->sem_base[semnum].semval == 0 &&
+				q->alter)
+			break;
+
 		error = try_atomic_semop(sma, q->sops, q->nsops,
 					 q->undo, q->pid);