Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758890AbXFMPvc (ORCPT ); Wed, 13 Jun 2007 11:51:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758288AbXFMPvY (ORCPT ); Wed, 13 Jun 2007 11:51:24 -0400 Received: from mail.screens.ru ([213.234.233.54]:45549 "EHLO mail.screens.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758256AbXFMPvX (ORCPT ); Wed, 13 Jun 2007 11:51:23 -0400 Date: Wed, 13 Jun 2007 19:51:24 +0400 From: Oleg Nesterov To: "Eric W. Biederman" Cc: will_schmidt@vnet.ibm.com, Andrew Morton , linuxppc-dev@ozlabs.org, Anton Blanchard , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] [PATCH i386] during VM oom condition, kill all threads in process group Message-ID: <20070613155124.GA275@tv-sign.ru> References: <20070605174831.21740.33119.stgit@farscape.rchland.ibm.com> <20070607153459.2a1b3230.akpm@linux-foundation.org> <20070607231621.GB32549@kryten> <20070607171018.d51fc5da.akpm@linux-foundation.org> <1181330358.21409.31.camel@farscape.rchland.ibm.com> <20070608123230.520655f5.akpm@linux-foundation.org> <1181337147.21409.42.camel@farscape.rchland.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1685 Lines: 44 On 06/08, Eric W. Biederman wrote: > > Will Schmidt writes: > > > On Fri, 2007-06-08 at 12:32 -0700, Andrew Morton wrote: > >> On Fri, 08 Jun 2007 14:19:18 -0500 > >> Will Schmidt wrote: > >> > >> > > > > zap_other_threads() requires tasklist_lock. > >> > > > > >> In fact, it's probably the case that rcu_read_lock() is now sufficient > >> locking coverage for zap_other_threads() (cc's people). > >> > >> It had better be, because do_group_exit() forgot to take tasklist_lock. It > >> is perhaps relying upon spin_lock()'s hidden rcu_read_lock() properties > >> without so much as a code comment, which would be somewhat nasty of it. > > > >> You could perhaps just call do_group_exit() from within the fault > >> handler, > >> btw. > > > > Yup, so looks like I can actually replace the existing do_exit() call > > with do_group_exit(). I'll sit on this for a bit to give other folks a > > chance to comment on which lock call is sufficient, read_lock() or > > rcu_read_lock(), etc; and do_group_exit()'s issue with taking > > tasklist_lock. > > No. The rcu_read_lock is not sufficient. > Yes. sighand->siglock is enough, and we explicitly take it in > do_group_exit before calling zap_other_threads. Yes, we don't need tasklist_lock (or rcu_read_lock). de_thread() calls zap_other_threads() under tasklist_lock, but this is because we can change child_reaper. 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/