I've been running this all night without seeing any problem.  I'm using 
current x86.git#testing with a few local patches, but nothing especially 
relevent-looking.

Could you try the attached patch to see if it makes any difference?

Meh .. what backend are you using?  We're using LVM volumes exported 
directly into the domUs like so:


Unfortunately we're still in the same place... pv_ops kernels are still 
hanging after heavy disk IO:

works - 2.6.18.x (from xen-unstable)
hangs - 2.6.25-rc3-git3
hangs - 2.6.25-rc3-git3 + your patch

Any other suggestions or debugging I can provide that would be useful to 
squash this?

-Chris

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Are you running an SMP or UP domain?  I found I could get hangs very 
easily with UP (but I need confirm it isn't a result of some other very 
experimental patches).

    J
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The hang occurs with both SMP and UP compiled pv_ops kernels.  SMP 
kernels are still slightly responsive after the hang occurs, which makes 
me think only one proc gets stuck at a time, not the entire kernel.

-Chris

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The patch I posted yesterday - "xen: fix RMW when unmasking events" - 
should definitively fix the hanging-under-load bugs (I hope).  It 
problem came from returning to userspace with pending events, which 
would leave them hanging around on the vcpu unprocessed, and eventually 
everything would deadlock.  This was caused by using an unlocked 
read-modify-write operation on the event pending flag - which can be set 
by another (real) cpu - meaning that the pending event wasn't noticed 
until too late.  It would only be a problem on an SMP host.

The patch should back-apply to 2.6.24.

    J
--

Confirmed-by: caker@theshore.net

Nice work!

-Chris

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