From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756739AbZBLGde (ORCPT ); Thu, 12 Feb 2009 01:33:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751127AbZBLGdZ (ORCPT ); Thu, 12 Feb 2009 01:33:25 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:64848 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1750785AbZBLGdY (ORCPT ); Thu, 12 Feb 2009 01:33:24 -0500 Message-ID: <4993C2A0.3050507@cn.fujitsu.com> Date: Thu, 12 Feb 2009 14:33:04 +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 , Andrew Morton , LKML , Arjan van de Ven 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> In-Reply-To: <20090212062442.GE28946@ZenIV.linux.org.uk> 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 >>>> 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. int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys, char *nodename) { ... mutex_lock(&cgroup_mutex); again: root = subsys->root; if (root == &rootnode) { <--- here mutex_unlock(&cgroup_mutex); return 0; } > Could you > a) add a printk to that sucker > b) independently from (a), see if wrapping these syscalls into > pid = fork(); > if (!pid) { > [make a syscall, print something] > exit(0); > } else if (pid > 0) { > waitpid(pid, NULL, 0); > } > and see what happens... > >