linux-kernel - Re: NFS causing oops when freeing namespace

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Message-ID: <20070117185823.GA878@tv-sign.ru>
Date:	Wed, 17 Jan 2007 21:58:23 +0300
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Daniel Hokka Zakrisson <daniel@...ac.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, herbert@...hfloor.at, akpm@...l.org,
	trond.myklebust@....uio.no,
	Linux Containers <containers@...ts.osdl.org>
Subject: Re: NFS causing oops when freeing namespace

On 01/17, Daniel Hokka Zakrisson wrote:
>
> >> Call Trace:
> >>  [<c03be6f0>] _spin_lock_irqsave+0x20/0x90
> >>  [<c01f6115>] lockd_down+0x125/0x190
> >>  [<c01d26bd>] nfs_free_server+0x6d/0xd0
> >>  [<c01d8e9c>] nfs_kill_super+0xc/0x20
> >>  [<c0161c5d>] deactivate_super+0x7d/0xa0
> >>  [<c0175e0e>] release_mounts+0x6e/0x80
> >>  [<c0175e86>] __put_mnt_ns+0x66/0x80
> >>  [<c0132b3e>] free_nsproxy+0x5e/0x60
> >>  [<c011f021>] do_exit+0x791/0x810
> >>  [<c011f0c6>] do_group_exit+0x26/0x70
> >>  [<c0103142>] sysenter_past_esp+0x5f/0x85
> >>  [<c03b0033>] rpc_wake_up+0x3/0x70
>
> It was the only semi-plausible explanation I could come up with. I added a
> printk in do_exit right before exit_task_namespaces, where sighand was
> still set, and one right before the spin_lock_irq in lockd_down, where it
> had suddenly been set to NULL.

I can't reproduce the problem, but

	do_exit:
		exit_notify(tsk);
		exit_task_namespaces(tsk);

the task could be reaped by its parent in between.

We should not use ->signal/->sighand after exit_notify().

Can we move exit_task_namespaces() up?

Oleg.

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