From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([140.186.70.92]:48030)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <anthony@codemonkey.ws>) id 1QRPID-0004Z7-Oo
	for qemu-devel@nongnu.org; Tue, 31 May 2011 09:47:34 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <anthony@codemonkey.ws>) id 1QRPIC-0003ko-MK
	for qemu-devel@nongnu.org; Tue, 31 May 2011 09:47:33 -0400
Message-ID: <4DE4F16D.6030009@codemonkey.ws>
Date: Tue, 31 May 2011 08:47:25 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
MIME-Version: 1.0
References: <1306705831-59385-1-git-send-email-andreas.faerber@web.de>
In-Reply-To: <1306705831-59385-1-git-send-email-andreas.faerber@web.de>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Subject: Re: [Qemu-devel] [PATCH] Use SIGIO with caution
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: =?UTF-8?B?QW5kcmVhcyBGw6RyYmVy?= <andreas.faerber@web.de>
Cc: qemu-trivial@nongnu.org, Jan Kiszka <jan.kiszka@siemens.com>, Marcelo Tosatti <mtosatti@redhat.com>, qemu-devel@nongnu.org, Avi Kivity <avi@redhat.com>

On 05/29/2011 04:50 PM, Andreas Färber wrote:
> BeOS and Haiku don't define SIGIO. When undefined, it won't arrive
> and doesn't need to be blocked.
>
> Signed-off-by: Andreas Färber<andreas.faerber@web.de>

Anything to do with signal masks is never a trivial patch BTW...

But I actually think explicit handling of SIGIO is unneeded.  I think 
this is a hold over from the pre-I/O thread days where we selectively 
set SIGIO on certain file descriptors to make sure that when an IO fd 
became readable, we received a signal to break out of the KVM emulation 
loop.

Can the folks on CC confirm/deny?

I can't see any use of SIGIO in the current source tree.

Regards,

Anthony Liguori

> ---
>   cpus.c |    8 ++++++++
>   1 files changed, 8 insertions(+), 0 deletions(-)
>
> diff --git a/cpus.c b/cpus.c
> index 1fc34b7..42af291 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -395,7 +395,9 @@ static int qemu_signal_init(void)
>       pthread_sigmask(SIG_UNBLOCK,&set, NULL);
>
>       sigemptyset(&set);
> +#ifdef SIGIO
>       sigaddset(&set, SIGIO);
> +#endif
>       sigaddset(&set, SIGALRM);
>       sigaddset(&set, SIG_IPI);
>       sigaddset(&set, SIGBUS);
> @@ -408,7 +410,9 @@ static int qemu_signal_init(void)
>            * We need to process timer signals synchronously to avoid a race
>            * between exit_request check and KVM vcpu entry.
>            */
> +#ifdef SIGIO
>           sigaddset(&set, SIGIO);
> +#endif
>           sigaddset(&set, SIGALRM);
>       }
>   #endif
> @@ -449,12 +453,16 @@ static void qemu_kvm_init_cpu_signals(CPUState *env)
>   #else
>       sigemptyset(&set);
>       sigaddset(&set, SIG_IPI);
> +#ifdef SIGIO
>       sigaddset(&set, SIGIO);
> +#endif
>       sigaddset(&set, SIGALRM);
>       pthread_sigmask(SIG_BLOCK,&set, NULL);
>
>       pthread_sigmask(SIG_BLOCK, NULL,&set);
> +#ifdef SIGIO
>       sigdelset(&set, SIGIO);
> +#endif
>       sigdelset(&set, SIGALRM);
>   #endif
>       sigdelset(&set, SIG_IPI);