disallowed nesting of key handlers (c/s 20929)

disallowed nesting of key handlers (c/s 20929)

[Jan Beulich]

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

Re: disallowed nesting of key handlers (c/s 20929)

[Jan Beulich]

Oh, and I also think the shared scratch buffer should be at least large
enough to dump NR_CPUS and MAX_VIRT_CPUS wide bitmaps.

Jan

>>> "Jan Beulich" <JBeulich@novell.com> 12.02.10 08:58 >>>
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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