From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757575AbZBLGzh (ORCPT ); Thu, 12 Feb 2009 01:55:37 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751215AbZBLGz2 (ORCPT ); Thu, 12 Feb 2009 01:55:28 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:58260 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751413AbZBLGz1 (ORCPT ); Thu, 12 Feb 2009 01:55:27 -0500 Message-ID: <4993C7C2.4060100@cn.fujitsu.com> Date: Thu, 12 Feb 2009 14:54:58 +0800 From: Li Zefan User-Agent: Thunderbird 2.0.0.9 (X11/20071115) MIME-Version: 1.0 To: Al Viro CC: containers@lists.osdl.org, Paul Menage , Arjan van de Ven , Andrew Morton , LKML Subject: Re: [cgroup or VFS ?] WARNING: at fs/namespace.c:636 mntput_no_expire+0xac/0xf2() References: <49617D35.4040805@cn.fujitsu.com> <20090209004046.3ce1dde0.akpm@linux-foundation.org> <20090209093414.GU28946@ZenIV.linux.org.uk> <499013CC.2060808@cn.fujitsu.com> <4993BD5D.2020707@cn.fujitsu.com> <20090212062442.GE28946@ZenIV.linux.org.uk> <4993C2A0.3050507@cn.fujitsu.com> In-Reply-To: <4993C2A0.3050507@cn.fujitsu.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Li Zefan wrote: >>>>> How cute... Same mountpoint in both, so these mount(2) will sometimes >>>>> fail (cgroup picks the same sb on the same options, AFAICS) and fail >>>>> silently due to these redirects... >>>>> >>>>> That's a lovely way to stress-test a large part of ro-bind stuff *and* >>>>> umount()-related code. Could you do C equivalent of the above (just >>>>> the same syscalls in loop, nothing fancier) and do time-stamped strace? >>>>> >>>> Sure, I'll write a C version and try to reproduce the warning. >>>> >>> Unfortunately, the C equivalent can't reproduce the warning, I've run the >>> test for the whole night. :( While using the script, often I can trigger >>> the warning in several mins. >> Ho-hum... I wonder if we are hitting cgroup_clone() in all that fun... > > I don't think so, I think cgroup_clone() will be called only if namespace is > used, like clone(CLONE_NEWNS). Even if cgroup_clone() gets called, it will > return before doing any vfs work unless the ns_cgroup subsystem is mounted. > But the following testcase can also trigger the warning: thread 1: for ((; ;)) { mount -t cgroup -o ns xxx cgroup/ > /dev/null 2>&1 # remove the dirs generated by cgroup_clone() rmdir cgroup/[1-9]* > /dev/null 2>&1 umount cgroup/ > /dev/null 2>&1 } thread 2: int foo(void *arg) { return 0; } char *stack[4096]; int main(int argc, char **argv) { int usec = DEFAULT_USEC; while (1) { usleep(usec); # cgroup_clone() will be called clone(foo, stack+4096, CLONE_NEWNS, NULL); } return 0; }