Messages in this thread | | | Date | Mon, 9 Feb 2009 00:40:46 -0800 | From | Andrew Morton <> | Subject | Re: [cgroup or VFS ?] WARNING: at fs/namespace.c:636 mntput_no_expire+0xac/0xf2() |
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(cc's added)
On Mon, 05 Jan 2009 11:23:33 +0800 Li Zefan <lizf@cn.fujitsu.com> 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: > for ((; ;)) > { > mount -t cpuset xxx /mnt > /dev/null 2>&1 > umount /mnt > /dev/null 2>&1 > } > > (Note: Again it is irrelevant which cgroup subsys is used.) > > After a while this showed up: > > ------------[ cut here ]------------ > WARNING: at fs/namespace.c:636 mntput_no_expire+0xac/0xf2() > Hardware name: Aspire SA85 > Modules linked in: bridge stp llc autofs4 dm_mirror dm_region_hash dm_log dm_mod r8169 parport_pc mii parport sg button sata_sis pata_sis ata_generic libata sd_mod scsi_mod ext3 jbd mbcache uhci_hcd ohci_hcd ehci_hcd [last unloaded: scsi_wait_scan] > Pid: 4745, comm: umount Not tainted 2.6.28 #479 > Call Trace: > [<c042bbe3>] warn_slowpath+0x79/0x8f > [<c044babf>] ? __lock_acquire+0x69a/0x700 > [<c04ae44e>] ? mntput_no_expire+0x79/0xf2 > [<c04ae481>] mntput_no_expire+0xac/0xf2 > [<c04ae968>] sys_umount+0x26a/0x2b1 > [<c04ae9c1>] sys_oldumount+0x12/0x14 > [<c0403251>] sysenter_do_call+0x12/0x31 > ---[ end trace 79d0ab4bef01333f ]--- > > The WARNING is: WARN_ON(atomic_read(&mnt->__mnt_writers));
OK, I'm all confused. Here we see a WARN_ON triggered, but in http://lkml.org/lkml/2009/1/4/352 with the same testcase we're seeing a lockdep warning.
You refer to Arjan's "lockdep: annotate sb ->s_umount" patch - but that's over two years old.
And you say "The changelog said s_umount needs to be classified as per-sb, but actually it made it as per-filesystem." But what is the difference between per-sb and per-fs?
More info here: http://bugzilla.kernel.org/show_bug.cgi?id=12673
This bug report seems to be all over the place.
Is it a post-2.6.28 regression, btw?
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