From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755432AbaDGT5H (ORCPT ); Mon, 7 Apr 2014 15:57:07 -0400 Received: from mout.gmx.net ([212.227.17.21]:56623 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753162AbaDGT5F (ORCPT ); Mon, 7 Apr 2014 15:57:05 -0400 Message-ID: <5343030C.3040004@gmx.de> Date: Mon, 07 Apr 2014 21:57:00 +0200 From: =?UTF-8?B?VG9yYWxmIEbDtnJzdGVy?= User-Agent: Mozilla/5.0 (X11; Linux i686; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Frederic Weisbecker CC: Peter Zijlstra , Michele Ballabio , linux-kernel@vger.kernel.org, mingo@kernel.org, Steven Rostedt Subject: Re: Bisected KVM hang on x86-32 between v3.12 and v3.13 References: <5341707F.5000406@katamail.com> <20140407150337.GO10526@twins.programming.kicks-ass.net> <20140407150705.GB13658@twins.programming.kicks-ass.net> <5342EB78.3060002@gmx.de> <20140407185949.GC4106@localhost.localdomain> In-Reply-To: <20140407185949.GC4106@localhost.localdomain> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Provags-ID: V03:K0:znOQWvHic+VTDX6rOuygL48d3zxK4onTzknkcmC/cZIvjLyVlOA DWaImo83dNPrQQUZU62Jllkoxll1rlIigQ95ztBFQJqZww3LdDzYvzStKMU+ZnwN3UZej3X S22U7URpztpdF8vqq8Nj9+UdmXTAU69eDBFU2xbXCT23JgYSFLA/6+rQrVW5fYwvhE9UxEB TpWgZS7m2QrzMQRGLYAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 On 04/07/2014 08:59 PM, Frederic Weisbecker wrote: > On Mon, Apr 07, 2014 at 08:16:24PM +0200, Toralf Förster wrote: >> -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 >> >> On 04/07/2014 05:07 PM, Peter Zijlstra wrote: >>> On Mon, Apr 07, 2014 at 05:03:37PM +0200, Peter Zijlstra >>> wrote: >>>> So what I suspect at this point is that because i386 and >>>> x86_64 have a difference in current_thread_info() (i386 is >>>> stack based), we end up setting the TIF_NEED_RESCHED bit on >>>> the wrong stack. >>>> >>>> Now I have some vague memories of propagating the TIF flags >>>> on stack switch, but I cannot remember what arch we did that >>>> for. Let me stare at this a little more. >>>> >>>> Also, IFF this is the case, then the fingered patch above >>>> (and your suggested 'fix') aren't the real curlpit/cure but >>>> simply make it more/less likely to happen. >>>> >>>> Now, Steve had a patch somewhere that would make i386 use >>>> per-cpu variables for current_thread_info() just like x86_64 >>>> already does I think. Let me go find them too. >>> >>> Ohh, goodie, they're already in Linus' tree. Could you see if >>> current git still suffers this problem? >>> >> v3.14-10353-g2b3a8fd works fine AFAICS (BTW the fix is stable >> material, right ?) > > If we are reffering to 198d208df4371734ac4728f69cb585c284d20a15 > (x86: Keep thread_info on thread stack in x86_32) it doesn't carry > a stable tag. > > So to be clear, you are saying that v3.14 is fine but other > release are buggy? Which ones are these? > No, 3.13.x and 3.14 have the issue, latest git is fine and 3.12.x > If a backport is needed, 198d208df4371734ac4728f69cb585c284d20a15 > looks too large... > - -- MfG/Sincerely Toralf Förster pgp finger print:1A37 6F99 4A9D 026F 13E2 4DCF C4EA CDDE 0076 E94E -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iF4EAREIAAYFAlNDAwwACgkQxOrN3gB26U5Z7AD+OMcd+262s1fJV9Fg8NjL5TaI Y4hZHzdv76fU/9P1lrkA/RUbQFYn6r9fZz61UrEIZ5lg5dUX04DDcQkfPUMZRow3 =Ifk8 -----END PGP SIGNATURE-----