linux-kernel - [PATCH 2/6] ipc/sem.c: Bugfix for semctl(,,GETZCNT)

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Date:	Sat, 10 May 2014 12:03:15 +0200
From:	Manfred Spraul <manfred@...orfullife.com>
To:	Davidlohr Bueso <davidlohr.bueso@...com>,
	Michael Kerrisk <mtk.manpages@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>, 1vier1@....de,
	Manfred Spraul <manfred@...orfullife.com>
Subject: [PATCH 2/6] ipc/sem.c: Bugfix for semctl(,,GETZCNT)

GETZCNT is supposed to return the number of threads that wait until
a semaphore value becomes 0.
The current implementation overlooks complex operations that contain
both wait-for-zero operation and operations that alter at least one semaphore.

The patch fixes that.
It's intentionally copy&paste, this will be cleaned up in the next patch.

Signed-off-by: Manfred Spraul <manfred@...orfullife.com>
---
 ipc/sem.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/ipc/sem.c b/ipc/sem.c
index 5749b9c..dc648f8 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -1047,6 +1047,16 @@ static int count_semzcnt(struct sem_array *sma, ushort semnum)
 			    && !(sops[i].sem_flg & IPC_NOWAIT))
 				semzcnt++;
 	}
+	list_for_each_entry(q, &sma->pending_alter, list) {
+		struct sembuf *sops = q->sops;
+		int nsops = q->nsops;
+		int i;
+		for (i = 0; i < nsops; i++)
+			if (sops[i].sem_num == semnum
+			    && (sops[i].sem_op == 0)
+			    && !(sops[i].sem_flg & IPC_NOWAIT))
+				semzcnt++;
+	}
 	return semzcnt;
 }
 
-- 
1.9.0

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