From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from [140.186.70.92] (port=39628 helo=eggs.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1P8pmO-0000wz-QV
	for qemu-devel@nongnu.org; Thu, 21 Oct 2010 03:41:42 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <paolo.bonzini@gmail.com>) id 1P8pmN-00044J-EN
	for qemu-devel@nongnu.org; Thu, 21 Oct 2010 03:41:40 -0400
Received: from mail-fx0-f45.google.com ([209.85.161.45]:48200)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <paolo.bonzini@gmail.com>) id 1P8pmN-00044C-62
	for qemu-devel@nongnu.org; Thu, 21 Oct 2010 03:41:39 -0400
Received: by fxm9 with SMTP id 9so3727617fxm.4
	for <qemu-devel@nongnu.org>; Thu, 21 Oct 2010 00:41:38 -0700 (PDT)
Sender: Paolo Bonzini <paolo.bonzini@gmail.com>
Message-ID: <4CBFEEAF.3070003@redhat.com>
Date: Thu, 21 Oct 2010 09:41:35 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
MIME-Version: 1.0
References: <cover.1287596626.git.mtosatti@redhat.com>
	<10ae5833ff9de153c311917d532f3e84e5b00387.1287596626.git.mtosatti@redhat.com>
	<4CBF485C.9060808@linux.vnet.ibm.com> <4CBF65A7.3090903@redhat.com>
	<4CBF6747.3020308@linux.vnet.ibm.com>
In-Reply-To: <4CBF6747.3020308@linux.vnet.ibm.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Subject: [Qemu-devel] Re: [PATCH 08/10] MCE: Relay UCR MCE to guest
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/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: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Anthony Liguori <aliguori@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>, qemu-devel@nongnu.org, kvm@vger.kernel.org, Avi Kivity <avi@redhat.com>

On 10/21/2010 12:03 AM, Anthony Liguori wrote:
>>
>> The timeout of qemu_kvm_eat_signal is always zero.
>
> So then qemu_kvm_eat_signal purely polls and it will happily keep
> polling as long as there is a signal pending.
>
> So what's the point of doing a sigtimedwait() and dropping qemu_mutex?

I agree that keeping the qemu_mutex makes sense if you remove the 
timeout argument (which I even have a patch for, as part of my Win32 
iothread series).  Until there is the theoretical possibility of 
suspending the process, qemu_kvm_eat_signal should drop the mutex.

> Why not just check sigpending in a loop?

Because sigtimedwait eats the signal, unlike sigpending (and sigsuspend).