ipc,sem: fix semctl(..., GETZCNT)

The semctl GETZCNT returns the number of semops waiting for the specified semaphore to become zero. After commit 9f1bc2c ("ipc,sem: have only one list in struct sem_queue"), the semops waiting on just one semaphore are waiting on that semaphore's list. In order to return the correct count, we have to walk that list too, in addition to the sem_array's list for complex operations. This bug broke dbench; it works again with this patch applied. Signed-off-by: Rik van Riel <[email protected]> Reported-by: Kent Overstreet <[email protected]> Tested-by: Kent Overstreet <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
gunnarahlberg · May 9, 2013 · ebc2e5e · ebc2e5e
1 parent 07e0745
commit ebc2e5e
Showing 1 changed file with 7 additions and 0 deletions.
diff --git a/ipc/sem.c b/ipc/sem.c
@@ -815,6 +815,13 @@ static int count_semzcnt (struct sem_array * sma, ushort semnum)
 	struct sem_queue * q;
 
 	semzcnt = 0;
+	list_for_each_entry(q, &sma->sem_base[semnum].sem_pending, list) {
+		struct sembuf * sops = q->sops;
+		BUG_ON(sops->sem_num != semnum);
+		if ((sops->sem_op == 0) && !(sops->sem_flg & IPC_NOWAIT))
+			semzcnt++;
+	}
+
 	list_for_each_entry(q, &sma->sem_pending, list) {
 		struct sembuf * sops = q->sops;
 		int nsops = q->nsops;