From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 7613 invoked by alias); 17 Dec 2009 20:27:31 -0000 Received: (qmail 7605 invoked by uid 22791); 17 Dec 2009 20:27:31 -0000 X-SWARE-Spam-Status: No, hits=-2.5 required=5.0 tests=AWL,BAYES_00,SPF_HELO_PASS,SPF_PASS X-Spam-Check-By: sourceware.org Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Thu, 17 Dec 2009 20:27:27 +0000 Received: from int-mx03.intmail.prod.int.phx2.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.16]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id nBHKRQsS027109 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Thu, 17 Dec 2009 15:27:26 -0500 Received: from ns3.rdu.redhat.com (ns3.rdu.redhat.com [10.11.255.199]) by int-mx03.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id nBHKRPxC027280; Thu, 17 Dec 2009 15:27:25 -0500 Received: from opsy.redhat.com (ovpn01.gateway.prod.ext.phx2.redhat.com [10.5.9.1]) by ns3.rdu.redhat.com (8.13.8/8.13.8) with ESMTP id nBHKROLa016591; Thu, 17 Dec 2009 15:27:24 -0500 Received: by opsy.redhat.com (Postfix, from userid 500) id 45F7C378286; Thu, 17 Dec 2009 13:27:24 -0700 (MST) From: Tom Tromey To: Jan Kratochvil Cc: gdb-patches@sourceware.org Subject: Re: [patch] testsuite: Fix a race by me - watchthreads-reorder.exp References: <20091217195026.GA21468@host0.dyn.jankratochvil.net> Reply-To: tromey@redhat.com Date: Thu, 17 Dec 2009 20:27:00 -0000 In-Reply-To: <20091217195026.GA21468@host0.dyn.jankratochvil.net> (Jan Kratochvil's message of "Thu, 17 Dec 2009 20:50:26 +0100") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org X-SW-Source: 2009-12/txt/msg00238.txt.bz2 >>>>> "Jan" == Jan Kratochvil writes: Jan> there is a bug explainable by man pthread_cond_signal: Jan> The [...] pthread_cond_signal() functions shall have no effect if Jan> there are no threads currently blocked on cond. Jan> + i = pthread_cond_wait (&thread1_tid_cond, &thread1_tid_mutex); Jan> + assert (i == 0); pthread_cond_wait can also spuriously wake up. The usual thing to do is call it in a loop that checks some condition. Then, have the signalling thread set the condition before calling pthread_cond_signal. Something like: while (thread1_tid == 0) pthread_cond_wait (...); This is race-free as long as the signalling thread also acquires the mutex associated with the condition. Is there some reason not to do this in this test case? Tom