[Xen-devel] Re: [PATCH 08/13] xen/pvticketlock: disable interrupts while blocking

[Peter Zijlstra <peterz@xxxxxxxxxxxxx>]

On Thu, 2011-09-01 at 17:55 -0700, Jeremy Fitzhardinge wrote:
> From: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
> 
> We need to make sure interrupts are disabled while we're relying on the
> contents of the per-cpu lock_waiting values, otherwise an interrupt
> handler could come in, try to take some other lock, block, and overwrite
> our values.

Would this make it illegal to take a spinlock from NMI context?

I know that its generally considered bad form, but there's at least one
spinlock that's only taken from NMI context and thus hasn't got any
deadlock potential.

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