From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754622AbXDXKcQ (ORCPT ); Tue, 24 Apr 2007 06:32:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754603AbXDXKcQ (ORCPT ); Tue, 24 Apr 2007 06:32:16 -0400 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:33799 "EHLO ebiederm.dsl.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753968AbXDXKcO (ORCPT ); Tue, 24 Apr 2007 06:32:14 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Andrew Morton Cc: Oleg Nesterov , Davide Libenzi , Ingo Molnar , Linus Torvalds , "Rafael J. Wysocki" , Roland McGrath , Rusty Russell , linux-kernel@vger.kernel.org, Subject: Re: [PATCH] kthread: Enhance kthread_stop to abort interruptible sleeps References: <20070413130236.GA173@tv-sign.ru> <20070424030924.be44ebfa.akpm@linux-foundation.org> Date: Tue, 24 Apr 2007 04:30:22 -0600 In-Reply-To: <20070424030924.be44ebfa.akpm@linux-foundation.org> (Andrew Morton's message of "Tue, 24 Apr 2007 03:09:24 -0700") Message-ID: User-Agent: Gnus/5.110006 (No Gnus v0.6) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Andrew Morton writes: > On Fri, 13 Apr 2007 21:13:13 -0600 ebiederm@xmission.com (Eric W. Biederman) > wrote: > >> This patch reworks kthread_stop so it is more flexible and it causes >> the target kthread to abort interruptible sleeps. Allowing a larger >> class of kernel threads to use to the kthread API. >> >> The changes start by defining TIF_KTHREAD_STOP on all architectures. >> TIF_KTHREAD_STOP is a per process flag that I can set from another >> process to indicate that a kernel thread should stop. >> >> wake_up_process in kthread_stop has been replaced by signal_wake_up >> ensuring that the kernel thread if sleeping is woken up in a timely >> manner and with TIF_SIGNAL_PENDING set, which causes us to break out >> of interruptible sleeps. >> >> recalc_signal_pending was modified to keep TIF_SIGNAL_PENDING set for >> as long as TIF_KTHREAD_STOP is set. >> >> Arbitrary paths to do_exit are now allowed. I have placed a >> completion on the thread stack and pointed vfork_done at it, when the >> mm_release is called from do_exit the completion will be called. >> Since the completion is stored on the stack it is important that >> kthread() now calls do_exit ensuring the stack frame that holds the >> completion is never released, and so that our exit_code is certain to >> make it unchanged all the way to do_exit. >> >> To allow kthread_stop to read the process exit code when exit_mm wakes >> it up I have moved the setting of exit_code to the beginning of >> do_exit. > > This patch causes this oops: http://userweb.kernel.org/~akpm/s5000508.jpg > with this config: http://userweb.kernel.org/~akpm/config-x.txt Thanks. If I am reading the oops properly this happened during bootup and vfork_done was set to NULL? The NULL vfork_done is really weird as exec is the only thing that sets vfork_done to NULL. Either I've got a stupid bug in there somewhere or we have just found the weirdest memory stomp. I will take a look and see if I can reproduce this shortly. Eric