From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arjan van de Ven Subject: Re: [cgroup or VFS ?] WARNING: at fs/namespace.c:636 mntput_no_expire+0xac/0xf2() Date: Mon, 9 Feb 2009 10:11:41 -0800 Message-ID: <20090209101141.42265319@infradead.org> References: <49617D35.4040805@cn.fujitsu.com> <20090209004046.3ce1dde0.akpm@linux-foundation.org> <20090209093414.GU28946@ZenIV.linux.org.uk> <1234201739.20090.194.camel@nimitz> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1234201739.20090.194.camel@nimitz> Sender: linux-kernel-owner@vger.kernel.org To: Dave Hansen Cc: Al Viro , Andrew Morton , containers@lists.osdl.org, Paul Menage , LKML List-Id: containers.vger.kernel.org On Mon, 09 Feb 2009 09:48:59 -0800 Dave Hansen wrote: > On Mon, 2009-02-09 at 09:34 +0000, Al Viro wrote: > > On Mon, Feb 09, 2009 at 12:40:46AM -0800, Andrew Morton wrote: > > > > Thread 1: > > > > for ((; ;)) > > > > { > > > > mount -t cgroup -o cpuset xxx /mnt > /dev/null 2>&1 > > > > mkdir /mnt/0 > /dev/null 2>&1 > > > > rmdir /mnt/0 > /dev/null 2>&1 > > > > umount /mnt > /dev/null 2>&1 > > > > } > > > > > > > > Thread 2: > > > > { > > > > mount -t cpuset xxx /mnt > /dev/null 2>&1 > > > > umount /mnt > /dev/null 2>&1 > > > > } > > > > 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? > > Could you also add a printk of what ->__mnt_writers was at the time of > the WARN_ON()? That will hopefully at least tell us whether we're > looking at a real leak or just a single missed mnt_want/drop_write(). > Also hopefully in which direction the thing is biased. With the mount > not being around long I'm not horribly hopeful, but it can't hurt. ... we could just change the WARN_ON to a WARN().. which has printk semantics ;) -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org