Re: [PATCH] generic ipi function calls: wait on alloc failurefallback

From: Ingo Molnar
Date: Fri Jul 18 2008 - 18:20:34 EST



* Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:

>> does this explain the xen64 weirdnesses you've been seeing?
>>
>
> No, but I haven't seen it lately. I think the other RCU fixes may
> have helped. But it's all a bit of a worry: I didn't have a good
> theory about what was going wrong, the RCU patches didn't look like
> they'd fix the symptoms I was seeing.
>
> I've seen it with 32 and 64-bit Xen, but there's nothing about the
> problem which makes me think it's really Xen specific. If it were,
> I'd expect to see failures all over the place, rather than in just in
> this one specific place.
>
> I'm concerned there's a lurking bug, particularly if it's a generic
> race or something that happens to be triggered when running under Xen
> because of the timing changes. I've tried reproducing it in a hvm Xen
> domain (so it's running the normal x86 kernel fully virtualized, but
> with the Xen scheduler, etc). I didn't see a problem, but it isn't a
> very convincing test one way or the other.

ok. I doubt there's much we can do at this stage - the code looks fine.
If it's some recently added core kernel problem sooner or later some
workload or hw will come about that shows it in a more debuggable
manner.

Ingo
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