Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754621AbXH0F7c (ORCPT ); Mon, 27 Aug 2007 01:59:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751675AbXH0F7Y (ORCPT ); Mon, 27 Aug 2007 01:59:24 -0400 Received: from x346.tv-sign.ru ([89.108.83.215]:36933 "EHLO mail.screens.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751447AbXH0F7X (ORCPT ); Mon, 27 Aug 2007 01:59:23 -0400 Date: Mon, 27 Aug 2007 09:57:31 +0400 From: Oleg Nesterov To: taoyue Cc: Sukadev Bhattiprolu , Andrew Morton , Alexey Dobriyan , Ingo Molnar , Thomas Gleixner , Roland McGrath , linux-kernel@vger.kernel.org, stable@kernel.org, Mark Zhan , "Ashfield, Bruce" Subject: Re: [PATCH] sigqueue_free: fix the race with collect_signal() Message-ID: <20070827055731.GA91@tv-sign.ru> References: <20070823134538.GA1358@tv-sign.ru> <46CEEA94.2070902@windriver.com> <20070824074558.GA86@tv-sign.ru> <46CF4DCB.6030304@windriver.com> <20070824110836.GA74@tv-sign.ru> <46CF3988.1020408@us.ibm.com> <20070824202305.GA274@tv-sign.ru> <46D2D57E.4070406@windriver.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <46D2D57E.4070406@windriver.com> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1495 Lines: 36 On 08/27, taoyue wrote: > > Oleg Nesterov wrote: > >On 08/24, Sukadev Bhattiprolu wrote: > >>>>> > >>>>I know, using current->sighand->siglock to prevent one sigqueue > >>>>is free twice. I want to know whether it is possible that the two > >>>>function is called in different thread. If that, the spin_lock is > >>>>useless. > >>>> > >>>> > >>>Not sure I understand. Yes, it is possible they are called by 2 different > >>>threads, that is why we had a race. But all threads in the same thread > >>>group have the same ->sighand, and thus the same ->sighand->siglock. > >>> > I has applied the new patch, and start test program last Friday. > So far, the test program has run for three days. Great, thanks. > In my test program, all threads is created in one process, so they > are in the same thread group. If two thread is not in the same thread > group, they have the different ->sighand->siglock. In this case, the > lock can't prevent the sigqueue object from race condition. If two thread are not in the same thread, they can't access the same SIGQUEUE_PREALLOC sigqueue. That is why sigqueue_free() uses current->sighand. Otherwise, this lock doesn't make any sense, and can't protect list_del(q->list). Oleg. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/