From owner-p4-projects@FreeBSD.ORG Tue Aug 15 16:02:39 2006 Return-Path: X-Original-To: p4-projects@freebsd.org Delivered-To: p4-projects@freebsd.org Received: by hub.freebsd.org (Postfix, from userid 32767) id BE04E16A4EB; Tue, 15 Aug 2006 16:02:39 +0000 (UTC) X-Original-To: perforce@freebsd.org Delivered-To: perforce@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 83D9B16A4DA; Tue, 15 Aug 2006 16:02:39 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from server.baldwin.cx (66-23-211-162.clients.speedfactory.net [66.23.211.162]) by mx1.FreeBSD.org (Postfix) with ESMTP id 8E07E43D73; Tue, 15 Aug 2006 16:02:38 +0000 (GMT) (envelope-from jhb@freebsd.org) Received: from localhost.corp.yahoo.com (john@localhost [127.0.0.1]) (authenticated bits=0) by server.baldwin.cx (8.13.6/8.13.6) with ESMTP id k7FG2Sbu028481; Tue, 15 Aug 2006 12:02:34 -0400 (EDT) (envelope-from jhb@freebsd.org) From: John Baldwin To: Divacky Roman Date: Tue, 15 Aug 2006 12:02:21 -0400 User-Agent: KMail/1.9.1 References: <200608151523.k7FFN7rN002736@repoman.freebsd.org> <200608151130.17341.jhb@freebsd.org> <20060815154418.GA60482@stud.fit.vutbr.cz> In-Reply-To: <20060815154418.GA60482@stud.fit.vutbr.cz> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200608151202.22197.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH authentication, not delayed by milter-greylist-2.0.2 (server.baldwin.cx [127.0.0.1]); Tue, 15 Aug 2006 12:02:35 -0400 (EDT) X-Virus-Scanned: ClamAV 0.88.3/1664/Tue Aug 15 10:28:31 2006 on server.baldwin.cx X-Virus-Status: Clean X-Spam-Status: No, score=-4.4 required=4.2 tests=ALL_TRUSTED,AWL,BAYES_00 autolearn=ham version=3.1.3 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on server.baldwin.cx Cc: Roman Divacky , Perforce Change Reviews Subject: Re: PERFORCE change 104043 for review X-BeenThere: p4-projects@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: p4 projects tree changes List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 15 Aug 2006 16:02:40 -0000 On Tuesday 15 August 2006 11:44, Divacky Roman wrote: > On Tue, Aug 15, 2006 at 11:30:16AM -0400, John Baldwin wrote: > > On Tuesday 15 August 2006 11:23, Roman Divacky wrote: > > > http://perforce.freebsd.org/chv.cgi?CH=104043 > > > > > > Change 104043 by rdivacky@rdivacky_witten on 2006/08/15 15:22:57 > > > > > > Grrrr. Do the locking/unlocking correctly this time. > > > > > > Affected files ... > > > > > > .. //depot/projects/soc2006/rdivacky_linuxolator/compat/linux/linux_futex.c#27 > > edit > > > > > > Differences ... > > > > > > > > ==== //depot/projects/soc2006/rdivacky_linuxolator/compat/linux/linux_futex.c#27 > > (text+ko) ==== > > > > > > @@ -339,9 +339,13 @@ > > > return f; > > > } > > > } > > > + if (locked == FUTEX_UNLOCKED) > > > + FUTEX_UNLOCK; > > > > > > /* Not found, create it */ > > > f = malloc(sizeof(*f), M_LINUX, M_WAITOK); > > > + if (locked == FUTEX_UNLOCKED) > > > + FUTEX_LOCK; > > > f->f_uaddr = uaddr; > > > f->f_refcount = 1; > > > TAILQ_INIT(&f->f_waiting_proc); > > > > This readds the race. :) See my other e-mail on what you have to do to handle > > it. > > what is wrong with unprotected malloc? the memory at which f points at is nowhere referenced > nowhere added etc. until protected by the lock. > > can you please explain me why is this wrong? I dont see any harm with two processes executing > this code paralelly. The problem is if both threads add a futex for the same address then you'll have two structures for the same futex. -- John Baldwin