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Date:      Fri, 6 Oct 1995 20:59:02 +0100
From:      se@zpr.uni-koeln.de (Stefan Esser)
To:        current@freebsd.org
Cc:        Doug Rabson <dfr@render.com>
Subject:   biodone: buffer already done (and system hangs) with -current
Message-ID:  <199510061959.AA04407@Sysiphos>

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There seems to be some problem in FreeBSD-current regarding mmap() and NFS:


Just found, that "tail -300" can hang forever in disk wait, if used to access 
some file via NFS:

$ ps -lw
  UID   PID  PPID CPU PRI NI   VSZ  RSS WCHAN  STAT  TT       TIME COMMAND
  200 27492 27459   0 -22  0   152  444 vmpfw  D+    p0    0:00.03 tail -300 /homes/se/Mail/fvwm


I've traced the point of failure to be the first access to the mmap()ed file 
(tail/forward.c:218).

Interestingly I can access the file by other means without problems (i.e. a 
cat of the same file succeeds).


On the console appeared 3 "biodone: buffer already done" messages per cat of 
the file (some 540KB).


The system didn't shutdown (i.e. hung before the "syncing disks" message), 
when I tried to reboot.

When the system was up again, I retried the tail command, and it hung again!
(I.e. I can reproduce this failure, in case you got something I might test.)

Any ideas ?

STefan

-- 
 Stefan Esser, Zentrum fuer Paralleles Rechnen		Tel:	+49 221 4706021
 Universitaet zu Koeln, Weyertal 80, 50931 Koeln	FAX:	+49 221 4705160
 ==============================================================================
 http://www.zpr.uni-koeln.de/staff/esser/esser.html	  <se@ZPR.Uni-Koeln.DE>



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