From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751566AbaEYSVL (ORCPT ); Sun, 25 May 2014 14:21:11 -0400 Received: from mail-wi0-f176.google.com ([209.85.212.176]:50623 "EHLO mail-wi0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751329AbaEYSVK (ORCPT ); Sun, 25 May 2014 14:21:10 -0400 From: Manfred Spraul To: Andrew Morton Cc: LKML , Davidlohr Bueso , Michael Kerrisk , 1vier1@web.de, Manfred Spraul Subject: [PATCH 7/6] ipc/sem.c: add a printk_once for semctl(GETNCNT/GETZCNT) Date: Sun, 25 May 2014 20:21:03 +0200 Message-Id: <1401042063-24666-1-git-send-email-manfred@colorfullife.com> X-Mailer: git-send-email 1.9.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The actual Linux implementation for semctl(GETNCNT) and semctl(GETZCNT) always (since 0.99.10) reported a thread as sleeping on all semaphores that are listed in the semop() call. The documented behavior (both in the Linux man page and in the Single Unix Specification) is that a task should be reported on exactly one semaphore: The semaphore that caused the thread to got to sleep. This patch adds a printk_once() that is triggered if a thread hits the relevant case. Signed-off-by: Manfred Spraul Cc: Davidlohr Bueso Cc: Michael Kerrisk --- ipc/sem.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/ipc/sem.c b/ipc/sem.c index 9106321..3cc2f7b6 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -1000,6 +1000,18 @@ static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q, { struct sembuf *sop = q->blocking; + /* + * Linux always (since 0.99.10) reported a task as sleeping on all + * semaphores. This violates SUS, therefore it was changed to the + * standard compliant behavior. + * Give the administrators a chance to notice that an application + * might misbehave because it relies on the Linux behavior. + */ + printk_once(KERN_INFO "semctl(GETNCNT/GETZCNT) is since 3.16 Single " \ + "Unix Specification compliant.\n" \ + "The task %d triggered the difference, " \ + "watch for misbehavior.", current->pid); + if (sop->sem_num != semnum) return 0; -- 1.9.0