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From: Neil Brown <neilb@cse.unsw.edu.au>
To: Byron Stanoszek <gandalf@winds.org>
Date: Tue, 6 Feb 2001 12:18:53 +1100 (EST)
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Message-ID: <14975.20733.827783.777739@notabene.cse.unsw.edu.au>
Cc: linux-kernel@vger.kernel.org, Trond Myklebust <trond.myklebust@fys.uio.no>
Subject: Re: NFS stop/start problems (related to datagram shutdown bug?)
In-Reply-To: message from Byron Stanoszek on Monday February 5
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On Monday February 5, gandalf@winds.org wrote:
> On Tue, 6 Feb 2001, Neil Brown wrote:
> 
> > How repeatable is this?  Is the server SMP?
> 
> I've tested this on two UP Athlons and 2 SMP Pentium 3's and the same problem
> occurred. I have not tested it more than once on the same system (I left the
> NFS servers untouched after the reboot).
> 
> The Athlon systems running NFS were 2.4.1-ac3 and the Pentiums were running
> 2.2.19-pre7. All computers exporting the FS had one directory mounted at least
> once.
> 
> In one case, only 1 directory was mounted once and then unmounted before
> shutting off the NFS server. When I realized I forgot to copy a directory over,
> I went to restart NFS on the server and found out I was unable to. Probably
> irrelevant, but this had been after transferring 7 gigs of data over 100 Mbps.
> 
> I still have the 'broken' server running, so if you would like me to run a
> command or two on it I can show you the results.

I don't think that there is much useful that I could look at, thanks.

> 
> > The attached patch might fix it, so if you are having reproducable
> > problems, it might be worth applying this patch.
> 
> I can try it tomorrow and see if it fixes the problem, but since this problem
> also occurred on a UP, using spin locks probably will not correct it. Perhaps
> it's something else.

On second thoughts, this doesn't need to be SMP related.  I don't know
much about "bottom halves" but I gather that they get run after an
interrupt has been handled and interrupts have been re-enabled, but
before the original process is rescheduled.  If this is the case, then
the "_bh" part of the "spin_lock_bh" (which does a local_bh_disable)
could be the bit that is important on a UP system.

NeilBrown


> 
> > [patch snipped]
> 
>  -Byron
> 
> -- 
> Byron Stanoszek                         Ph: (330) 644-3059
> Systems Programmer                      Fax: (330) 644-8110
> Commercial Timesharing Inc.             Email: byron@comtime.com
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