netdev - Re: nfs client hang

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Message-ID: <4C515384.6030905@bluearc.com>
Date:	Thu, 29 Jul 2010 11:10:12 +0100
From:	Andy Chittenden <andyc@...earc.com>
To:	Chuck Lever <chuck.lever@...cle.com>
CC:	Eric Dumazet <eric.dumazet@...il.com>,
	"Linux Kernel Mailing List (linux-kernel@...r.kernel.org)" 
	<linux-kernel@...r.kernel.org>,
	Trond Myklebust <trond.myklebust@....uio.no>,
	netdev <netdev@...r.kernel.org>,
	Linux NFS Mailing List <linux-nfs@...r.kernel.org>
Subject: Re: nfs client hang

  On 2010-07-28 18:37, Chuck Lever wrote:
> On 07/28/10 03:24 AM, Andy Chittenden wrote:
>> resending as it seems to have been corrupted on LKML!
>>
>>> The RPC client marks the socket closed. and the linger timeout is
>>> cancelled.  At this point, sk_shutdown should be set to zero, correct?
>>> I don't see an xs_error_report() call here, which would confirm that the
>>> socket took a trip through tcp_disconnect().
>>  From my reading of tcp_disconnect(), it calls sk->sk_error_report(sk)
>> unconditionally so as there's no xs_error_report(), that surely means
>> the exact opposite: tcp_disconnect() wasn't called. If it's not
>> called, sk_shutdown is not cleared. And my revised tracing confirmed
>> that it was set to SEND_SHUTDOWN.
> Sorry, that's what I meant above.
>
> An xs_error_report() debugging message at that point in the log would
> confirm that the socket took a trip through tcp_disconnect().  But I
> don't see such a message.
I don't see how tcp_disconnect() gets called if the application does a 
shutdown when the state is TCP_ESTABLISHED (or a myriad of other 
states). It just seems to send a FIN. Should tcp_disconnect() be called? 
If so, how? Alternatively, I wonder whether my patch that set 
sk_shutdown to 0 in tcp_connect_init() is the correct fix after all.

-- 
Andy, BlueArc Engineering

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