stopping amd causes a freeze

[Artem Belevich]

On Mon, Jul 22, 2013 at 2:50 AM, Dominic Fandrey <kamikaze at bsdforen.de>wrote:

> Occasionally stopping amd freezes my system. It's a rare occurrence,
> and I haven't found a reliable way to reproduce it.
>
> It's also a real freeze, so there's no way to get into the debugger
> or grab a core dump. I only can perform the 4 seconds hard shutdown to
> revive the system.
>
> I run amd through sysutils/automounter, which is a scripting solution
> that generates an amd.map file based on encountered devices and devd
> events. The SIGHUP it sends to amd to tell it the map file was updated
> does not cause problems, only a SIGKILL may cause the freeze.
>
> Nothing was mounted (by amd) during the last freeze.
>
>
amd itself is a primitive NFS server as far as system is concerned and amd
mount points are mounted from it. If you just KILL it without giving it a
chance to clean things up you'll potentially end up in a situation similar
to mounting from remote NFS server that's unresponsive. From mount_nfs(8):

     If the server becomes unresponsive while an NFS file system is mounted,
     any new or outstanding file operations on that file system will hang
     uninterruptibly until the server comes back.  To modify this default
be-
     haviour, see the intr and soft options.



> I don't see any angle to tackle this, but I'm throwing it out here
> any way, in the hopes that someone actually has an idea how to approach
> the issue.
>

Don't use KILL or make sure that nobody tries to use amd mountpoints until
new instance starts. Manually unmounting them before killing amd may help.
Why not let amd do it itself with "/etc/rc.d/amd stop" ?

--Artem


>
> # uname -a
> FreeBSD mobileKamikaze.norad 9.2-PRERELEASE FreeBSD 9.2-PRERELEASE #0
> r253413: Wed Jul 17 13:12:46 CEST 2013     root at mobileKamikaze.norad:/usr/obj/HP6510b-91/amd64/usr/src/sys/HP6510b-91
>  amd64
>
> That's amd's starting message:
> Jul 22 11:32:28 mobileKamikaze amd[8176]/info:  no logfile defined; using
> stderr
> Jul 22 11:32:28 mobileKamikaze amd[8176]/info:  AM-UTILS VERSION
> INFORMATION:
> Jul 22 11:32:28 mobileKamikaze amd[8176]/info:  Copyright (c) 1997-2006
> Erez Zadok
> Jul 22 11:32:28 mobileKamikaze amd[8176]/info:  Copyright (c) 1990
> Jan-Simon Pendry
> Jul 22 11:32:28 mobileKamikaze amd[8176]/info:  Copyright (c) 1990
> Imperial College of Science, Technology & Medicine
> Jul 22 11:32:28 mobileKamikaze amd[8176]/info:  Copyright (c) 1990 The
> Regents of the University of California.
> Jul 22 11:32:28 mobileKamikaze amd[8176]/info:  am-utils version 6.1.5
> (build 901505).
> Jul 22 11:32:28 mobileKamikaze amd[8176]/info:  Report bugs to
> https://bugzilla.am-utils.org/ or am-utils at am-utils.org.
> Jul 22 11:32:28 mobileKamikaze amd[8176]/info:  Configured by David
> O'Brien <obrien at FreeBSD.org> on date 4-December-2007 PST.
> Jul 22 11:32:28 mobileKamikaze amd[8176]/info:  Built by
> root at mobileKamikaze.norad.
> Jul 22 11:32:28 mobileKamikaze amd[8176]/info:  cpu=amd64 (little-endian),
> arch=amd64, karch=amd64.
> Jul 22 11:32:28 mobileKamikaze amd[8176]/info:  full_os=freebsd9.2,
> os=freebsd9, osver=9.2, vendor=undermydesk, distro=The FreeBSD Project.
> Jul 22 11:32:28 mobileKamikaze amd[8176]/info:  domain=norad,
> host=mobileKamikaze, hostd=mobileKamikaze.norad.
> Jul 22 11:32:28 mobileKamikaze amd[8176]/info:  Map support for: root,
> passwd, union, nis, ndbm, file, exec, error.
> Jul 22 11:32:28 mobileKamikaze amd[8176]/info:  AMFS: nfs, link, nfsx,
> nfsl, host, linkx, program, union, ufs, cdfs,
> Jul 22 11:32:28 mobileKamikaze amd[8176]/info:        pcfs, auto, direct,
> toplvl, error, inherit.
> Jul 22 11:32:28 mobileKamikaze amd[8176]/info:  FS: cd9660, nfs, nfs3,
> nullfs, msdosfs, ufs, unionfs.
> Jul 22 11:32:28 mobileKamikaze amd[8176]/info:  Network 1:
> wire="192.168.1.0" (netnumber=192.168.1).
> Jul 22 11:32:28 mobileKamikaze amd[8176]/info:  Network 2:
> wire="192.168.0.0" (netnumber=192.168).
> Jul 22 11:32:28 mobileKamikaze amd[8176]/info:  My ip addr is 127.0.0.1
>
> amd is called with the flags -r -p -a -c 4 -w 2
>
> --
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> Q: Why is top-posting such a bad thing?
> A: Top-posting.
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