From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:48985)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <sw@weilnetz.de>) id 1a1ufl-00038A-A4
	for qemu-devel@nongnu.org; Thu, 26 Nov 2015 06:25:10 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <sw@weilnetz.de>) id 1a1ufh-0006ZB-CN
	for qemu-devel@nongnu.org; Thu, 26 Nov 2015 06:25:09 -0500
Received: from smtp.mail.uni-mannheim.de ([134.155.96.80]:39277)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <sw@weilnetz.de>) id 1a1ufh-0006XN-6c
	for qemu-devel@nongnu.org; Thu, 26 Nov 2015 06:25:05 -0500
References: <565485A0.5090902@sysgo.com> <5654883F.9050509@redhat.com>
	<56557AA2.9080100@sysgo.com> <5655AA1F.8060906@sysgo.com>
	<5655B706.6060306@redhat.com> <5655BFEA.50407@sysgo.com>
	<5655C781.8090201@redhat.com> <5655D848.9050104@sysgo.com>
	<5655DEE2.20700@redhat.com> <5656CCE3.2050504@sysgo.com>
From: Stefan Weil <sw@weilnetz.de>
Message-ID: <5656EC15.1010909@weilnetz.de>
Date: Thu, 26 Nov 2015 12:25:09 +0100
MIME-Version: 1.0
In-Reply-To: <5656CCE3.2050504@sysgo.com>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [PATCH v2] qemu_mutex_iothread_locked not
 correctly synchronized
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: David Engraf <david.engraf@sysgo.com>, Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org
Cc: Fam Zheng <famz@redhat.com>

Am 26.11.2015 um 10:12 schrieb David Engraf:
> Am 25.11.2015 um 17:16 schrieb Paolo Bonzini:
>>
>>
>> On 25/11/2015 16:48, David Engraf wrote:
>>>
>>> Indeed, TLS handling is broken. The address of iothread_locked is
>>> always
>>> the same between threads and I can see that a different thread sets
>>> iothread_locked to false, thus my current thread uses an invalid state.
>>> I will have to check why my compiler produces invalid TLS code.
>>
>> That rings a bell, I think there are different CRT libraries or
>> something like that.  Stefan, what would break TLS under Windows?
>
> "--extra-cflags=-mthreads" is the solution. iothread_locked is unique
> for each thread now. I saw that this is already mentioned in the
> Documentation [1], but why isn't that enabled by default if QEMU
> requires this option on Windows? Without this option, even the latest
> version of gcc doesn't produce working TLS code.
>
> Many thanks for your support!
>
> David
>
> [1] http://wiki.qemu.org/Hosts/W32

Hi David,

I just prepared a patch which will enable that option by default
for all compilations targeting Windows.

Thanks for your report!

Regards,
Stefan