From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Jan Beulich" <JBeulich@novell.com>
Subject: Re: [RFC][PATCH] walking the page lists needs the
	page_alloc lock
Date: Fri, 13 Aug 2010 08:06:31 +0100
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	<C88AA8E0.1D980%keir.fraser@eu.citrix.com>
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To: Keir Fraser <keir.fraser@eu.citrix.com>
Cc: Tim Deegan <Tim.Deegan@eu.citrix.com>, "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>
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>>> On 13.08.10 at 08:46, Keir Fraser <keir.fraser@eu.citrix.com> wrote:
> On 13/08/2010 07:40, "Jan Beulich" <JBeulich@novell.com> wrote:
>=20
>>> Sorry, my intention was to say that changes to the debug-key printouts
>>> are safe, not that they didn't require changes.
>>>=20
>>> The debug-key printouts (in particular the NUMA one) are where I
>>> actually hit this bug on a running system.
>>=20
>> But then, to avoid a hanging system, these should be trylock-s
>> rather than plain locks, shouldn't they?
>=20
> Why? The handler is called in softirq context. It should be safe to =
spin.

Hmm, indeed. I was looking at others, and at least
domain_dump_evtchn_info() also uses a trylock - apparently for
no good reason.

Jan