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From: Alexandre Raymond <cerbere@gmail.com>
Date: Wed, 8 Jun 2011 19:19:33 -0400
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Subject: Re: [Qemu-devel] [PATCH] sigfd: use pthread_sigmask
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To: Alexander Graf <agraf@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>, =?UTF-8?Q?Andreas_F=C3=A4rber?= <andreas.faerber@web.de>, qemu-devel Developers <qemu-devel@nongnu.org>, Jan Kiszka <jan.kiszka@siemens.com>

On Wed, Jun 8, 2011 at 6:55 PM, Alexander Graf <agraf@suse.de> wrote:
> Qemu uses signalfd to figure out, if a signal occured without the need
> to actually receive the signal. Instead, it can read from the fd to recei=
ve
> its news.
>
> Now, we obviously don't always have signalfd around. Especially not on
> non-Linux systems. So what we do there is that we create a new thread,
> block that thread on all signals and simply call sigwait to wait for a
> signal we're interested in to occur.
>
> This all sounds great, but what we're really doing is:
>
> =C2=A0 =C2=A0sigset_t all;
>
> =C2=A0 =C2=A0sigfillset(&all);
> =C2=A0 =C2=A0sigprocmask(SIG_BLOCK, &all, NULL);
>
> which - on Darwin - blocks all signals on the current _process_, not only
> on the current thread. To block signals on the thread, we can use
> pthread_sigmask().
>
> This patch does that, assuming that my above analysis is correct, and thu=
s
> renders Qemu useable on Darwin again.
I confirm that Qemu works much better on Darwin with this patch :)

Thanks!
Alexandre