From: Stanislav Kinsbursky <skinsbursky@parallels.com>
To: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Mark Lord <kernel@teksavvy.com>, <linux-nfs@vger.kernel.org>,
Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: BUG at net/sunrpc/svc_xprt.c:921
Date: Thu, 17 Jan 2013 17:24:14 +0400 [thread overview]
Message-ID: <50F7FB7E.2020503@parallels.com> (raw)
In-Reply-To: <20130117130335.GD6598@fieldses.org>
17.01.2013 17:03, J. Bruce Fields пишет:
> On Thu, Jan 17, 2013 at 09:05:51AM +0400, Stanislav Kinsbursky wrote:
>> 17.01.2013 02:51, Mark Lord пишет:
>>> On 13-01-16 12:20 AM, Stanislav Kinsbursky wrote:
>>>>
>>>> Mark, could you provide any call traces?
>>>
>>> Call traces from where/what?
>>> There's this one, posted earlier in the BUG report:
>>>
>>> kernel BUG at net/sunrpc/svc_xprt.c:921!
>>> Call Trace:
>>> [<ffffffffa016a56a>] ? svc_recv+0xcc/0x338 [sunrpc]
>>> [<ffffffffa0318bfc>] ? nfs_callback_authenticate+0x20/0x20 [nfsv4]
>>> [<ffffffffa0318c19>] ? nfs4_callback_svc+0x1d/0x3c [nfsv4]
>>> [<ffffffff810407e6>] ? kthread+0x81/0x89
>>> [<ffffffff81040765>] ? kthread_freezable_should_stop+0x36/0x36
>>> [<ffffffff812ea62c>] ? ret_from_fork+0x7c/0xb0
>>> [<ffffffff81040765>] ? kthread_freezable_should_stop+0x36/0x36
>>>
>>
>> Thanks!
>> I haven't seen the bug report.
>> Could you provide the link, please?
>
> There's no bz if that's what you're asking for.
>
> See the first message in the thread for the original report:
>
> http://mid.gmane.org/<50F42F85.50907@teksavvy.com>
>
Thanks, Bruce.
This looks like the old issue I was trying to fix with "SUNRPC: protect service sockets lists during per-net shutdown".
So, here is the problem as I see it: there is a transport, which is processed by service thread and it's processing is racing with per-net service shutdown:
CPU#0: CPU#1:
svc_recv svc_close_net
svc_get_next_xprt (list_del_init(xpt_ready))
svc_close_list (set XPT_BUSY and XPT_CLOSE)
svc_clear_pools(xprt was gained on CPU#0 already)
svc_delete_xprt (set XPT_DEAD)
svc_handle_xprt (is XPT_CLOSE => svc_delete_xprt()
BUG()
So, from my POW, we need some way to:
1) Skip such in-progress transports on svc_close_net() call (there is not way to detect them, or at least I don't see one)
2) Delete the transport after somewhere after svc_xprt_received()
But there is a problem with svc_xprt_received(): there is a call for svc_xprt_put() in it (svc_recv->svc_handle_xprt->svc_xprt_received->svc_xprt_put) . And if
we are the only user - then the transport will be destroyed. But transport is dereferenced later in svc_recv() after the svc_handle_xprt call.
What do you think, Bruce?
> --b.
>
--
Best regards,
Stanislav Kinsbursky
next prev parent reply other threads:[~2013-01-17 13:24 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-14 16:17 BUG at net/sunrpc/svc_xprt.c:921 Mark Lord
2013-01-14 20:37 ` J. Bruce Fields
2013-01-15 4:16 ` Mark Lord
2013-01-15 20:56 ` J. Bruce Fields
2013-01-16 5:20 ` Stanislav Kinsbursky
2013-01-16 22:51 ` Mark Lord
2013-01-16 22:58 ` Mark Lord
2013-01-17 5:05 ` Stanislav Kinsbursky
2013-01-17 13:03 ` J. Bruce Fields
2013-01-17 13:24 ` Stanislav Kinsbursky [this message]
2013-01-17 23:41 ` Mark Lord
2013-01-18 5:37 ` Stanislav Kinsbursky
2013-01-18 15:48 ` Mark Lord
2013-01-18 15:56 ` J. Bruce Fields
2013-01-21 8:19 ` Stanislav Kinsbursky
2013-01-20 22:51 ` BUG at net/sunrpc/svc_xprt.c:921 (another one) Mark Lord
2013-02-12 20:52 ` J. Bruce Fields
2013-02-13 15:00 ` Mark Lord
2013-02-15 19:22 ` J. Bruce Fields
2013-02-15 19:42 ` Tom Horsley
2013-02-15 19:46 ` J. Bruce Fields
2013-02-15 19:23 ` [PATCH 1/2] svcrpc: make svc_age_temp_xprts enqueue under sv_lock J. Bruce Fields
2013-02-15 19:23 ` [PATCH 2/2] svcrpc: fix rpc server shutdown races J. Bruce Fields
2013-02-15 19:33 ` BUG at net/sunrpc/svc_xprt.c:921 (another one) Paweł Sikora
2013-02-17 15:54 ` J. Bruce Fields
2013-02-18 7:42 ` Paweł Sikora
2013-01-17 13:11 ` BUG at net/sunrpc/svc_xprt.c:921 Mark Lord
2013-01-17 13:53 ` J. Bruce Fields
2013-01-17 23:40 ` Mark Lord
2013-02-25 20:45 ` Mark Lord
2013-02-25 20:52 ` J. Bruce Fields
-- strict thread matches above, loose matches on Subject: below --
2013-02-07 12:56 Tom Horsley
2013-02-08 20:58 ` J. Bruce Fields
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