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[Xen-devel] Re: [PATCH] xen: events: do not unmask polled ipis on restor

To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: [Xen-devel] Re: [PATCH] xen: events: do not unmask polled ipis on restore.
From: Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>
Date: Fri, 29 Oct 2010 18:35:09 +0100
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On Fri, 2010-10-29 at 17:44 +0100, Jeremy Fitzhardinge wrote:
> On 10/29/2010 01:33 AM, Ian Campbell wrote:
> > The Xen PV spinlock backend attempts to setup an IPI to IRQ binding
> > which is only to be used via xen_poll_irq rather received directly.
> >
> > Unfortunately restore_cpu_ipis unconditionally unmasks each IPI
> > leading to:
> Gosh I wonder why we hadn't seen this before?

I must admit I don't normally enable CONFIG_PARAVIRT_SPINLOCKS I
happened to be running someone else's config when I noticed this.

Possibly relates to switching to the edge triggered handler and the
related mask/unmask vs clear etc frobbing?

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