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Re: [Xen-devel] hanging tapdisk2 processes and improper udev rules

To: Daniel Stodden <daniel.stodden@xxxxxxxxxx>
Subject: Re: [Xen-devel] hanging tapdisk2 processes and improper udev rules
From: Sébastien RICCIO <sr@xxxxxxxxxxxxxxx>
Date: Fri, 22 Jul 2011 12:01:25 +0200
Cc: Andreas Olsowski <andreas.olsowski@xxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
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The processes, really? Where do they hang? (check out the wait state --
ps -eopid,wchan:25,cmd or so).

Or do you mean they're stuck waiting for I/Os?


They seems to work and to do their job, but they are in a strange state. For example a ps -aux on dom0 hangs when processing the line about the tapdisk process, also it cannot be detached from the vm, and issuing a reboot of the host hangs too (can't kill the process so it doesn't reboot).

I fighted quite a lot with this on a debian6 + xen 4.1.x box and found out that disabling the multipath-tools and multipath-tools-boot corrected the problem (but I need them). I thought that maybe it was beacause multipathd try to "multipath" the block device
handled by blktap2 and somehow locks it. But it's speculations :)

I do not have the the hands on the box at the moment to give you more informations and do not want to hijack this thread. It's just that it looked like the problem I encountered, but I will send you more informations when I am on the box.


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