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[Xen-devel] disallowed nesting of key handlers (c/s 20929)

To: "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx>
Subject: [Xen-devel] disallowed nesting of key handlers (c/s 20929)
From: "Jan Beulich" <JBeulich@xxxxxxxxxx>
Date: Fri, 12 Feb 2010 07:58:20 +0000
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Keir,

I don't think this is a good idea. In the course of analyzing issues with
tmem we had at least one case where this restriction would have
severely hindered debugging: The '0' handler wasn't able to put a
target vCPU to sleep (due to it spinning on a lock in the hypervisor),
and only the subsequent 'd' information really indicated what was
going on.

Generally expecting 'd' to be issued first also doesn't seem adequate
since that may not produce output in the case of a pCPU spinning
with interrupts disabled (whereas '0' in that case still has a chance
to produce useful output).

Jan


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