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Wed, 2 Oct 2019 11:05:59 +0000 From: Jan Glauber To: Paolo Bonzini Subject: Re: [Qemu-devel] qemu_futex_wait() lockups in ARM64: 2 possible issues Thread-Topic: [Qemu-devel] qemu_futex_wait() lockups in ARM64: 2 possible issues Thread-Index: AQHVeRFen3KZ7K8mD02pkgA8c1cuvA== Date: Wed, 2 Oct 2019 11:05:59 +0000 Message-ID: <20191002110550.GA3482@hc> References: <1864070a-2f84-1d98-341e-f01ddf74ec4b@ubuntu.com> <20190924202517.GA21422@xps13.dannf> <20191002092253.GA3857@hc> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-clientproxiedby: AM0PR10CA0056.EURPRD10.PROD.OUTLOOK.COM (2603:10a6:20b:150::36) To DM6PR18MB3001.namprd18.prod.outlook.com (2603:10b6:5:182::15) x-ms-exchange-messagesentrepresentingtype: 1 x-originating-ip: [109.42.2.12] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: e7d98316-6b95-4f2c-992c-08d74728814a x-ms-traffictypediagnostic: DM6PR18MB2362: x-ms-exchange-purlcount: 1 x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:6108; 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charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: e7d98316-6b95-4f2c-992c-08d74728814a X-MS-Exchange-CrossTenant-originalarrivaltime: 02 Oct 2019 11:05:59.2576 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 70e1fb47-1155-421d-87fc-2e58f638b6e0 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: xK+wbFx59S6OXXyUO0Pz1HoEOiUrGg8SCeeVjz1l1q+0JdgYw78OrnL7fvczoe3DD/QhrocgCJczSakk0ij8hA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR18MB2362 X-OriginatorOrg: marvell.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,1.0.8 definitions=2019-10-02_06:2019-10-01,2019-10-02 signatures=0 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] [fuzzy] X-Received-From: 67.231.156.173 X-Mailman-Approved-At: Wed, 02 Oct 2019 08:27:28 -0400 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Rafael David Tinoco , lizhengui , dann frazier , QEMU Developers , Bug 1805256 <1805256@bugs.launchpad.net>, QEMU Developers - ARM Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Oct 02, 2019 at 11:45:19AM +0200, Paolo Bonzini wrote: > On 02/10/19 11:23, Jan Glauber wrote: > > I've tried to verify me theory with this patch and didn't run into the > > issue for ~500 iterations (usually I would trigger the issue ~20 iterat= ions). >=20 > Awesome! That would be a compiler bug though, as atomic_add and atomic_s= ub > are defined as sequentially consistent: >=20 > #define atomic_add(ptr, n) ((void) __atomic_fetch_add(ptr, n, __ATOMIC_SE= Q_CST)) > #define atomic_sub(ptr, n) ((void) __atomic_fetch_sub(ptr, n, __ATOMIC_SE= Q_CST)) Compiler bug sounds kind of unlikely... > What compiler are you using and what distro? Can you compile util/aio-po= six.c > with "-fdump-rtl-all -fdump-tree-all", zip the boatload of debugging file= s and > send them my way? This is on Ubuntu 18.04.3, gcc version 7.4.0 (Ubuntu/Linaro 7.4.0-1ubuntu1~18.04.1) I've uploaded the debug files to: https://bugs.launchpad.net/qemu/+bug/1805256/+attachment/5293619/+files/aio= -posix.tar.xz Thanks, Jan > Thanks, >=20 > Paolo From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B95E4C35280 for ; Wed, 2 Oct 2019 12:33:14 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9046E2133F for ; Wed, 2 Oct 2019 12:33:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9046E2133F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=marvell.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:54886 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iFdof-0003pB-1C for qemu-devel@archiver.kernel.org; Wed, 02 Oct 2019 08:33:13 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35219) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iFcc1-00060d-Va for qemu-devel@nongnu.org; Wed, 02 Oct 2019 07:16:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iFcbz-00070W-I4 for qemu-devel@nongnu.org; Wed, 02 Oct 2019 07:16:05 -0400 Received: from indium.canonical.com ([91.189.90.7]:37268) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1iFcbx-0006wW-JY for qemu-devel@nongnu.org; Wed, 02 Oct 2019 07:16:02 -0400 Received: from loganberry.canonical.com ([91.189.90.37]) by indium.canonical.com with esmtp (Exim 4.86_2 #2 (Debian)) id 1iFcbv-0003r0-G1 for ; Wed, 02 Oct 2019 11:15:59 +0000 Received: from loganberry.canonical.com (localhost [127.0.0.1]) by loganberry.canonical.com (Postfix) with ESMTP id 768272E80CD for ; Wed, 2 Oct 2019 11:15:59 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Date: Wed, 02 Oct 2019 11:05:59 -0000 From: Jan Glauber To: qemu-devel@nongnu.org X-Launchpad-Notification-Type: bug X-Launchpad-Bug: product=qemu; status=In Progress; importance=Undecided; assignee=rafaeldtinoco@kernelpath.com; X-Launchpad-Bug: distribution=ubuntu; sourcepackage=qemu; component=main; status=In Progress; importance=Medium; assignee=rafaeldtinoco@kernelpath.com; X-Launchpad-Bug: distribution=ubuntu; distroseries=bionic; sourcepackage=qemu; component=main; status=New; importance=Undecided; assignee=None; X-Launchpad-Bug: distribution=ubuntu; distroseries=disco; sourcepackage=qemu; component=main; status=New; importance=Undecided; assignee=None; X-Launchpad-Bug: distribution=ubuntu; distroseries=eoan; sourcepackage=qemu; component=main; status=In Progress; importance=Medium; assignee=rafaeldtinoco@kernelpath.com; X-Launchpad-Bug: distribution=ubuntu; distroseries=ff-series; sourcepackage=qemu; component=None; status=New; importance=Undecided; assignee=None; X-Launchpad-Bug-Tags: qemu-img X-Launchpad-Bug-Information-Type: Public X-Launchpad-Bug-Private: no X-Launchpad-Bug-Security-Vulnerability: no X-Launchpad-Bug-Commenters: dannf jan-glauber-i jnsnow lizhengui rafaeldtinoco X-Launchpad-Bug-Reporter: dann frazier (dannf) X-Launchpad-Bug-Modifier: Jan Glauber (jan-glauber-i) References: <154327283728.15443.11625169757714443608.malonedeb@soybean.canonical.com> Message-Id: <20191002110550.GA3482@hc> Subject: [Bug 1805256] Re: [Qemu-devel] qemu_futex_wait() lockups in ARM64: 2 possible issues X-Launchpad-Message-Rationale: Subscriber (QEMU) @qemu-devel-ml X-Launchpad-Message-For: qemu-devel-ml Precedence: bulk X-Generated-By: Launchpad (canonical.com); Revision="19066"; Instance="production-secrets-lazr.conf" X-Launchpad-Hash: 5d09170f53216dae3245a3ab8a48577751fe2ed5 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 91.189.90.7 X-Mailman-Approved-At: Wed, 02 Oct 2019 08:27:28 -0400 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Bug 1805256 <1805256@bugs.launchpad.net> Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Message-ID: <20191002110559.jT0-zlOjb-BPAAVUz2C_QbO_iLZ7w0IOx9xP3M9wAro@z> On Wed, Oct 02, 2019 at 11:45:19AM +0200, Paolo Bonzini wrote: > On 02/10/19 11:23, Jan Glauber wrote: > > I've tried to verify me theory with this patch and didn't run into the > > issue for ~500 iterations (usually I would trigger the issue ~20 iterat= ions). > = > Awesome! That would be a compiler bug though, as atomic_add and atomic_s= ub > are defined as sequentially consistent: > = > #define atomic_add(ptr, n) ((void) __atomic_fetch_add(ptr, n, __ATOMIC_SE= Q_CST)) > #define atomic_sub(ptr, n) ((void) __atomic_fetch_sub(ptr, n, __ATOMIC_SE= Q_CST)) Compiler bug sounds kind of unlikely... > What compiler are you using and what distro? Can you compile util/aio-po= six.c > with "-fdump-rtl-all -fdump-tree-all", zip the boatload of debugging file= s and > send them my way? This is on Ubuntu 18.04.3, gcc version 7.4.0 (Ubuntu/Linaro 7.4.0-1ubuntu1~18.04.1) I've uploaded the debug files to: https://bugs.launchpad.net/qemu/+bug/1805256/+attachment/5293619/+files/aio= -posix.tar.xz Thanks, Jan > Thanks, > = > Paolo -- = You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1805256 Title: qemu-img hangs on rcu_call_ready_event logic in Aarch64 when converting images Status in QEMU: In Progress Status in qemu package in Ubuntu: In Progress Status in qemu source package in Bionic: New Status in qemu source package in Disco: New Status in qemu source package in Eoan: In Progress Status in qemu source package in FF-Series: New Bug description: Command: qemu-img convert -f qcow2 -O qcow2 ./disk01.qcow2 ./output.qcow2 Hangs indefinitely approximately 30% of the runs. ---- Workaround: qemu-img convert -m 1 -f qcow2 -O qcow2 ./disk01.qcow2 ./output.qcow2 Run "qemu-img convert" with "a single coroutine" to avoid this issue. ---- (gdb) thread 1 ... (gdb) bt #0 0x0000ffffbf1ad81c in __GI_ppoll #1 0x0000aaaaaabcf73c in ppoll #2 qemu_poll_ns #3 0x0000aaaaaabd0764 in os_host_main_loop_wait #4 main_loop_wait ... (gdb) thread 2 ... (gdb) bt #0 syscall () #1 0x0000aaaaaabd41cc in qemu_futex_wait #2 qemu_event_wait (ev=3Dev@entry=3D0xaaaaaac86ce8 ) #3 0x0000aaaaaabed05c in call_rcu_thread #4 0x0000aaaaaabd34c8 in qemu_thread_start #5 0x0000ffffbf25c880 in start_thread #6 0x0000ffffbf1b6b9c in thread_start () (gdb) thread 3 ... (gdb) bt #0 0x0000ffffbf11aa20 in __GI___sigtimedwait #1 0x0000ffffbf2671b4 in __sigwait #2 0x0000aaaaaabd1ddc in sigwait_compat #3 0x0000aaaaaabd34c8 in qemu_thread_start #4 0x0000ffffbf25c880 in start_thread #5 0x0000ffffbf1b6b9c in thread_start ---- (gdb) run Starting program: /usr/bin/qemu-img convert -f qcow2 -O qcow2 ./disk01.ext4.qcow2 ./output.qcow2 [New Thread 0xffffbec5ad90 (LWP 72839)] [New Thread 0xffffbe459d90 (LWP 72840)] [New Thread 0xffffbdb57d90 (LWP 72841)] [New Thread 0xffffacac9d90 (LWP 72859)] [New Thread 0xffffa7ffed90 (LWP 72860)] [New Thread 0xffffa77fdd90 (LWP 72861)] [New Thread 0xffffa6ffcd90 (LWP 72862)] [New Thread 0xffffa67fbd90 (LWP 72863)] [New Thread 0xffffa5ffad90 (LWP 72864)] [Thread 0xffffa5ffad90 (LWP 72864) exited] [Thread 0xffffa6ffcd90 (LWP 72862) exited] [Thread 0xffffa77fdd90 (LWP 72861) exited] [Thread 0xffffbdb57d90 (LWP 72841) exited] [Thread 0xffffa67fbd90 (LWP 72863) exited] [Thread 0xffffacac9d90 (LWP 72859) exited] [Thread 0xffffa7ffed90 (LWP 72860) exited] """ All the tasks left are blocked in a system call, so no task left to call qemu_futex_wake() to unblock thread #2 (in futex()), which would unblock thread #1 (doing poll() in a pipe with thread #2). Those 7 threads exit before disk conversion is complete (sometimes in the beginning, sometimes at the end). ---- [ Original Description ] On the HiSilicon D06 system - a 96 core NUMA arm64 box - qemu-img frequently hangs (~50% of the time) with this command: qemu-img convert -f qcow2 -O qcow2 /tmp/cloudimg /tmp/cloudimg2 Where "cloudimg" is a standard qcow2 Ubuntu cloud image. This qcow2->qcow2 conversion happens to be something uvtool does every time it fetches images. Once hung, attaching gdb gives the following backtrace: (gdb) bt #0 0x0000ffffae4f8154 in __GI_ppoll (fds=3D0xaaaae8a67dc0, nfds=3D187650= 274213760, =C2=A0=C2=A0=C2=A0=C2=A0timeout=3D, timeout@entry=3D0x0, s= igmask=3D0xffffc123b950) =C2=A0=C2=A0=C2=A0=C2=A0at ../sysdeps/unix/sysv/linux/ppoll.c:39 #1 0x0000aaaabbefaf00 in ppoll (__ss=3D0x0, __timeout=3D0x0, __nfds=3D, =C2=A0=C2=A0=C2=A0=C2=A0__fds=3D) at /usr/include/aarch64-= linux-gnu/bits/poll2.h:77 #2 qemu_poll_ns (fds=3D, nfds=3D, =C2=A0=C2=A0=C2=A0=C2=A0timeout=3Dtimeout@entry=3D-1) at util/qemu-timer.= c:322 #3 0x0000aaaabbefbf80 in os_host_main_loop_wait (timeout=3D-1) =C2=A0=C2=A0=C2=A0=C2=A0at util/main-loop.c:233 #4 main_loop_wait (nonblocking=3D) at util/main-loop.c:497 #5 0x0000aaaabbe2aa30 in convert_do_copy (s=3D0xffffc123bb58) at qemu-im= g.c:1980 #6 img_convert (argc=3D, argv=3D) at qemu-= img.c:2456 #7 0x0000aaaabbe2333c in main (argc=3D7, argv=3D) at qemu= -img.c:4975 Reproduced w/ latest QEMU git (@ 53744e0a182) To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1805256/+subscriptions