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Re: [Qemu-devel] [PATCH] Fix signal handling of SIG_IPI when io-thread i


From: Alexandre Raymond
Subject: Re: [Qemu-devel] [PATCH] Fix signal handling of SIG_IPI when io-thread is enabled
Date: Fri, 8 Jul 2011 22:33:24 -0400

ping?

On Wed, Jun 15, 2011 at 10:11 AM, Alexandre Raymond <address@hidden> wrote:
> Hi Jan,
>
>> Why? Ahh, because of qemu_cpu_kick_self: raise(SIG_IPI)! That should
>> generate a per-process SIG_IPI. And that may not only affect Darwin.
>> Looks good.
>
> Actually, with io-thread enabled, it goes through qemu_cpu_kick_self()
> -> qemu_cpu_kick_thread() -> pthread_kill(..., SIG_IPI).
>
> I think the problem is with sigwait(). It doesn't state so in the
> Linux or Darwin man pages, but on Solaris, it says : "All signals
> identified by the set argument must be blocked on all threads,
> including the calling thread; otherwise, sigwait() might not work
> correctly", which might correspond to the issue I've been witnessing
> (ie: sigwait() unblocking once in a while on a SIGUSR1 (SIG_IPI) in
> the event thread).
>
> In any case, I don't think it should attempt to catch this signal at
> all since the cpu thread is already catching it.
>
> Alexandre
>



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