Deadlock in fileserver lance driver

[jmk@plan9.att.com jmk@plan9.att.com]

I'm not sure what the locks are doing there at all, I don't know what they
are protecting.

The magnum fs kernel was cloned from the power kernel on March 13 1992 and
the power kernel had the locks in at that time. They disappeared from the power
kernel on May 15th 1992. The sparc kernel was cloned from the magnum kernel on
August 16th 1992 and /sys/src/fs/ss/lance.c has not changed since.

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>From cse.psu.edu!9fans-outgoing-owner Wed Aug  9 03:40:18 EDT 1995
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Date:	Wed, 9 Aug 1995 03:04:59 -0400
From:	dhog@plan9.cs.su.oz.au
To:	9fans@cse.psu.edu
Subject: Deadlock in fileserver lance driver
Message-Id: <95Aug9.031902edt.34090@psuvax1.cse.psu.edu>
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I have encountered a deadlock in the lance driver for the fileserver
kernel.  It seems to be aggravated by our slow jukebox :-)  Anyway,
here is my fix (a similar change should be made to the other fs kernels).

diff /n/dump/1995/0806/sys/src/fs/ss/lance.c /sys/src/fs/ss/lance.c
212a213
> 			qunlock(c);
213a215
> 			qlock(c);
215a218
> 			qunlock(c);
216a220
> 			qlock(c);