From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:32842) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z2c9b-00006y-Ip for qemu-devel@nongnu.org; Wed, 10 Jun 2015 05:18:39 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Z2c9W-00014P-LR for qemu-devel@nongnu.org; Wed, 10 Jun 2015 05:18:35 -0400 Received: from e06smtp17.uk.ibm.com ([195.75.94.113]:40243) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z2c9W-00010m-D1 for qemu-devel@nongnu.org; Wed, 10 Jun 2015 05:18:30 -0400 Received: from /spool/local by e06smtp17.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 10 Jun 2015 10:18:27 +0100 Received: from b06cxnps4075.portsmouth.uk.ibm.com (d06relay12.portsmouth.uk.ibm.com [9.149.109.197]) by d06dlp02.portsmouth.uk.ibm.com (Postfix) with ESMTP id 810B4219004D for ; Wed, 10 Jun 2015 10:18:04 +0100 (BST) Received: from d06av12.portsmouth.uk.ibm.com (d06av12.portsmouth.uk.ibm.com [9.149.37.247]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id t5A9IPmJ23330838 for ; Wed, 10 Jun 2015 09:18:25 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 t5A9IP6g002097 for ; Wed, 10 Jun 2015 03:18:25 -0600 Message-ID: <557800E0.5020202@de.ibm.com> Date: Wed, 10 Jun 2015 11:18:24 +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> In-Reply-To: <20150610021224.GE10873@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 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? >>> >>> Christian, I can't reproduce this on my x86 box with virtio-blk-pci. Do you >>> have a reproducer for x86? Or could you collect backtraces for all the threads >>> in QEMU when it hangs? >>> >>> My long shot is that the main loop is blocked at aio_context_acquire(ctx), >>> while the iothread of that ctx is blocked at aio_poll(ctx, blocking). >> >> Here is a backtrace on s390. I need 2 or more disks, (one is not enough). > > It shows iothreads and main loop are all waiting for events, and the vcpu > threads are running guest code. > > It could be the requests being leaked. Do you see this problem with a regular > file based image or null-co driver? Maybe we're missing something about the > AioContext in block/null.c. It seems to run with normal file based images. As soon as I have two or more null-aio devices it hangs pretty soon when doing a reboot loop. Christian