Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758096AbXHXLGf (ORCPT ); Fri, 24 Aug 2007 07:06:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755923AbXHXLG0 (ORCPT ); Fri, 24 Aug 2007 07:06:26 -0400 Received: from x346.tv-sign.ru ([89.108.83.215]:51725 "EHLO mail.screens.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755845AbXHXLGZ (ORCPT ); Fri, 24 Aug 2007 07:06:25 -0400 Date: Fri, 24 Aug 2007 15:08:36 +0400 From: Oleg Nesterov To: taoyue Cc: Andrew Morton , Alexey Dobriyan , Ingo Molnar , Thomas Gleixner , Roland McGrath , linux-kernel@vger.kernel.org, stable@kernel.org Subject: Re: [PATCH] sigqueue_free: fix the race with collect_signal() Message-ID: <20070824110836.GA74@tv-sign.ru> References: <20070823134538.GA1358@tv-sign.ru> <46CEEA94.2070902@windriver.com> <20070824074558.GA86@tv-sign.ru> <46CF4DCB.6030304@windriver.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <46CF4DCB.6030304@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: 1848 Lines: 50 On 08/24, taoyue wrote: > > Oleg Nesterov wrote: > >> > >>collect_signal: sigqueue_free: > >> > >> list_del_init(&first->list); > >> spin_lock_irqsave(lock, flags); > >> > > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > > >> if (!list_empty(&q->list)) > >> list_del_init(&q->list); > >> spin_unlock_irqrestore(lock, > >> flags); > >> q->flags &= ~SIGQUEUE_PREALLOC; > >> > >> __sigqueue_free(first); __sigqueue_free(q); > >> > > > >collect_signal() is always called under ->siglock which is also taken by > >sigqueue_free(), so this is not possible. > > > >Basically, this patch is the same one-liner I sent you before > > > > http://marc.info/?l=linux-kernel&m=118772206603453&w=2 > > > >(Thanks for the additional testing and report, btw). > > > >P.S. It would be nice to know if this patch solves the problems reported > >by Jeremy, but his email is disabled. > > > >Oleg. > > > > > 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. 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/