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Message-ID: <1341184071.2588.10.camel@pasglop>
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Mon, 02 Jul 2012 09:07:51 +1000
In-Reply-To: <4FF04939.7050608@ozlabs.ru>
References: <4FF02F2C.30006@ozlabs.ru> <20120701124314.GB4782@redhat.com>
	<4FF04939.7050608@ozlabs.ru>
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Subject: Re: [Qemu-devel] QEMU question: is eventfd not thread safe?
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To: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: Alex Williamson <alex.williamson@redhat.com>, David Gibson <david@gibson.dropbear.id.au>, qemu-devel@nongnu.org, "Michael S. Tsirkin" <mst@redhat.com>

> >> diff --git a/iohandler.c b/iohandler.c
> >> index 3c74de6..54f4c48 100644
> >> --- a/iohandler.c
> >> +++ b/iohandler.c
> >> @@ -77,6 +77,7 @@ int qemu_set_fd_handler2(int fd,
> >>          ioh->fd_write = fd_write;
> >>          ioh->opaque = opaque;
> >>          ioh->deleted = 0;
> >> +        kill(getpid(), SIGUSR2);
> >>      }
> >>      return 0;
> >>  }

That probably wants to be a pthread_kill targetted at the main loop.

> >> +static void sigusr2_print(int signal)
> >> +{
> >> +}
> >> +
> >> +static void sigusr2_init(void)
> >> +{
> >> +    struct sigaction action;
> >> +
> >> +    memset(&action, 0, sizeof(action));
> >> +    sigfillset(&action.sa_mask);
> >> +    action.sa_handler = sigusr2_print;
> >> +    action.sa_flags = 0;
> >> +    sigaction(SIGUSR2, &action, NULL);
> >> +}
> >> +

Won't that conflict with the business in coroutine-sigaltstack.c ?

Hrm... looking at it, it looks like it will save/restore the handler,
so that should be good.
 
Still, one might want to wrap that into something, like
qemu_wake_main_loop();

Cheers,
Ben.

> >>  int main_loop_init(void)
> >>  {
> >>      int ret;
> >>  
> >> +    sigusr2_init();
> >> +
> >>      qemu_mutex_lock_iothread();
> >>      ret = qemu_signal_init();
> >>      if (ret) {
> >> -- 
> >> 1.7.10
> 
>