From: Willy Tarreau <w@1wt.eu>
Date: Mon, 6 Feb 2017 07:59:06 +0000 (+0100)
Subject: Revert "ipc/sem.c: optimize sem_lock()"
X-Git-Tag: v3.10.105~38
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3d971ee18fe6ca21b722ce2c7e7a1d834d60929b;p=thirdparty%2Fkernel%2Fstable.git

Revert "ipc/sem.c: optimize sem_lock()"

This reverts commit 901f6fedc5340d66e2ca67c70dfee926cb5a1ea0
(upstream commit 6d07b68ce16ae9535955ba2059dedba5309c3ca1).

As suggested in commit 5864a2fd3088db73d47942370d0f7210a807b9bc
(ipc/sem.c: fix complex_count vs. simple op race) since it introduces
a regression and the candidate fix requires too many changes for 3.10.

Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---

diff --git a/ipc/sem.c b/ipc/sem.c
index 47a15192b8b87..3b968a028ccf1 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -267,20 +267,12 @@ static void sem_rcu_free(struct rcu_head *head)
  * Caller must own sem_perm.lock.
  * New simple ops cannot start, because simple ops first check
  * that sem_perm.lock is free.
- * that a) sem_perm.lock is free and b) complex_count is 0.
  */
 static void sem_wait_array(struct sem_array *sma)
 {
 	int i;
 	struct sem *sem;
 
-	if (sma->complex_count)  {
-		/* The thread that increased sma->complex_count waited on
-		 * all sem->lock locks. Thus we don't need to wait again.
-		 */
-		return;
-	}
-
 	for (i = 0; i < sma->sem_nsems; i++) {
 		sem = sma->sem_base + i;
 		spin_unlock_wait(&sem->lock);