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

ebc2e5e6 · Rik van Riel <[email protected]> · 2013-05-09 16:53:28 -04:00

The semctl GETZCNT returns the number of semops waiting for the
specified semaphore to become zero.  After commit 9f1bc2c9022c
("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]>

Commit: ebc2e5e6a408a0e6ed63c0ba98c2c8a232c6b4f4
Parents: 07e07450

Changes

1 files changed · +7 −0

File	Status	Add	Del	Content
ipc/sem.c	modified	+7	−0	View file

ipc/sem.c

View file

diff --git a/ipc/sem.c b/ipc/sem.c
index 899b598..04b264d 100644
--- 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;