Re: percpu related boot crash on x86

From: Pekka Enberg
Date: Thu Jan 20 2011 - 03:31:13 EST


On 1/20/11 1:11 AM, Ingo Molnar wrote:

* Ingo Molnar<mingo@xxxxxxx> wrote:

Btw., based on Peter's suggestion i tried the limit-bumping hack below - but it
did not help, the crash still triggers on 5%-10% of all randconfig bootups.

I'm now running tests with MAXSMP forcibly disabled - and there are no crashes after
69 randconfig iteration. Before it would crash within 10 iterations.

So it seems the MAXSMP sizing tests triggers a new percpu regression.

It needs CONFIG_DEBUG_PAGEALLOC to trigger. As the comment in vmap_debug_free_range() already says "it's going to be slow" I wonder if we could just hack around the problem by adding a

if (!irqs_disabled())

guard around the debugging code to make vfree() always work with IRQs disabled.

Pekka
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