From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50406) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZFgx6-0004zW-Kr for qemu-devel@nongnu.org; Thu, 16 Jul 2015 07:03:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZFgx2-0004oe-HW for qemu-devel@nongnu.org; Thu, 16 Jul 2015 07:03:44 -0400 Received: from e06smtp17.uk.ibm.com ([195.75.94.113]:54604) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZFgx2-0004oF-9O for qemu-devel@nongnu.org; Thu, 16 Jul 2015 07:03:40 -0400 Received: from /spool/local by e06smtp17.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 16 Jul 2015 12:03:37 +0100 Received: from b06cxnps3075.portsmouth.uk.ibm.com (d06relay10.portsmouth.uk.ibm.com [9.149.109.195]) by d06dlp02.portsmouth.uk.ibm.com (Postfix) with ESMTP id 3CC58219005C for ; Thu, 16 Jul 2015 12:03:13 +0100 (BST) Received: from d06av12.portsmouth.uk.ibm.com (d06av12.portsmouth.uk.ibm.com [9.149.37.247]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id t6GB3aoD24641770 for ; Thu, 16 Jul 2015 11:03:36 GMT Received: from d06av12.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av12.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id t6GI371W000868 for ; Thu, 16 Jul 2015 12:03:07 -0600 Message-ID: <55A78F87.9030805@de.ibm.com> Date: Thu, 16 Jul 2015 13:03:35 +0200 From: Christian Borntraeger MIME-Version: 1.0 References: <556DBF87.2020908@de.ibm.com> <20150609022832.GA12817@cpc-pc.redhat.com> <5576AB52.8090708@de.ibm.com> <20150610021224.GE10873@ad.nay.redhat.com> <557800E0.5020202@de.ibm.com> <20150610093408.GC11648@ad.nay.redhat.com> In-Reply-To: <20150610093408.GC11648@ad.nay.redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] "iothread: release iothread around aio_poll" causes random hangs at startup List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Fam Zheng Cc: Kevin Wolf , Paolo Bonzini , qemu-devel , Stefan Hajnoczi Am 10.06.2015 um 11:34 schrieb Fam Zheng: > On Wed, 06/10 11:18, Christian Borntraeger wrote: >> Am 10.06.2015 um 04:12 schrieb Fam Zheng: >>> On Tue, 06/09 11:01, Christian Borntraeger wrote: >>>> Am 09.06.2015 um 04:28 schrieb Fam Zheng: >>>>> On Tue, 06/02 16:36, Christian Borntraeger wrote: >>>>>> Paolo, >>>>>> >>>>>> I bisected >>>>>> commit a0710f7995f914e3044e5899bd8ff6c43c62f916 >>>>>> Author: Paolo Bonzini >>>>>> AuthorDate: Fri Feb 20 17:26:52 2015 +0100 >>>>>> Commit: Kevin Wolf >>>>>> CommitDate: Tue Apr 28 15:36:08 2015 +0200 >>>>>> >>>>>> iothread: release iothread around aio_poll >>>>>> >>>>>> to cause a problem with hanging guests. >>>>>> >>>>>> Having many guests all with a kernel/ramdisk (via -kernel) and >>>>>> several null block devices will result in hangs. All hanging >>>>>> guests are in partition detection code waiting for an I/O to return >>>>>> so very early maybe even the first I/O. >>>>>> >>>>>> Reverting that commit "fixes" the hangs. >>>>>> Any ideas? For what its worth, I can no longer reproduce the issue on current master + cherry-pick of a0710f7995f (iothread: release iothread around aio_poll) bisect tells me that commit 53ec73e264f481b79b52efcadc9ceb8f8996975c Author: Fam Zheng AuthorDate: Fri May 29 18:53:14 2015 +0800 Commit: Stefan Hajnoczi CommitDate: Tue Jul 7 14:27:14 2015 +0100 block: Use bdrv_drain to replace uncessary bdrv_drain_all made the problem will blk-null go away. I still dont understand why. Christian