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WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.85.222.193 Subject: [Qemu-devel] qemu_futex_wait() lockups in ARM64: 2 possible issues 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: Bug 1805256 <1805256@bugs.launchpad.net>, QEMU Developers - ARM , QEMU Developers Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Paolo, While debugging hungs in ARM64 while doing a simple: qemu-img convert -f qcow2 -O qcow2 file.qcow2 output.qcow2 I might have found 2 issues which I'd like you to review, if possible. ISSUE #1 ======== I've caught the following stack trace after an HUNG in qemu-img convert: (gdb) bt #0 syscall () #1 0x0000aaaaaabd41cc in qemu_futex_wait #2 qemu_event_wait (ev=ev@entry=0xaaaaaac86ce8 ) #3 0x0000aaaaaabed05c in call_rcu_thread #4 0x0000aaaaaabd34c8 in qemu_thread_start #5 0x0000ffffbf25c880 in start_thread #6 0x0000ffffbf1b6b9c in thread_start () (gdb) print rcu_call_ready_event $4 = {value = 4294967295, initialized = true} value INT_MAX (4294967295) seems WRONG for qemu_futex_wait(): - EV_BUSY, being -1, and passed as an argument qemu_futex_wait(void *, unsigned), is a two's complement, making argument into a INT_MAX when that's not what is expected (unless I missed something). *** If that is the case, unsure if you, Paolo, prefer declaring *(QemuEvent)->value as an integer or changing EV_BUSY to "2" would okay here *** BUG: description: https://bugs.launchpad.net/qemu/+bug/1805256/comments/15 ======== ISSUE #2 ======== I found this when debugging lockups while in futex() in a specific ARM64 server - https://bugs.launchpad.net/qemu/+bug/1805256 - which I'm still investigating. After fixing the issue above, I'm still getting stuck into: qemu_event_wait() -> qemu_futex_wait() *** As if qemu_event_set() has ran before qemu_futex_wait() ever started running *** The Other threads are waiting for poll() on a PIPE coming from this stuck thread (thread #1), and in sigwait(): (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=ev@entry=0xaaaaaac86ce8 ) #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 QUESTION: - Should qemu_event_set() check return code from qemu_futex_wake()->qemu_futex()->syscall() in order to know if ANY waiter was ever woken up ? Maybe even loop until at least 1 is awaken ? Tks in advance, Rafael D. Tinoco 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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 158B4C49ED9 for ; Wed, 11 Sep 2019 02:26:47 +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 DF7152168B for ; Wed, 11 Sep 2019 02:26:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DF7152168B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernelpath.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:46072 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i7sLF-00071W-Uj for qemu-devel@archiver.kernel.org; Tue, 10 Sep 2019 22:26:45 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:60657) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i7sKC-0006CA-K6 for qemu-devel@nongnu.org; Tue, 10 Sep 2019 22:25:41 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i7sKB-0000RJ-96 for qemu-devel@nongnu.org; Tue, 10 Sep 2019 22:25:40 -0400 Received: from indium.canonical.com ([91.189.90.7]:40292) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1i7sKB-0000Qk-3s for qemu-devel@nongnu.org; Tue, 10 Sep 2019 22:25:39 -0400 Received: from loganberry.canonical.com ([91.189.90.37]) by indium.canonical.com with esmtp (Exim 4.86_2 #2 (Debian)) id 1i7sK9-0001I2-4U for ; Wed, 11 Sep 2019 02:25:37 +0000 Received: from loganberry.canonical.com (localhost [127.0.0.1]) by loganberry.canonical.com (Postfix) with ESMTP id 1EC5E2E80CC for ; Wed, 11 Sep 2019 02:25:37 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Date: Wed, 11 Sep 2019 02:15:00 -0000 From: Rafael David Tinoco 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-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 jnsnow lizhengui rafaeldtinoco X-Launchpad-Bug-Reporter: dann frazier (dannf) X-Launchpad-Bug-Modifier: Rafael David Tinoco (rafaeldtinoco) References: <154327283728.15443.11625169757714443608.malonedeb@soybean.canonical.com> Message-Id: 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="19044"; Instance="production-secrets-lazr.conf" X-Launchpad-Hash: 326280af9e9fe57bd29bf2e0a4e30ed70287dafa X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 91.189.90.7 Subject: [Qemu-devel] [Bug 1805256] qemu_futex_wait() lockups in ARM64: 2 possible issues 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: <20190911021500.TfpxfkCK7Tz0gt8F42I0ZKHO2C-jnpk7YiOhTf4GeSM@z> Paolo, While debugging hungs in ARM64 while doing a simple: qemu-img convert -f qcow2 -O qcow2 file.qcow2 output.qcow2 I might have found 2 issues which I'd like you to review, if possible. ISSUE #1 =3D=3D=3D=3D=3D=3D=3D=3D I've caught the following stack trace after an HUNG in qemu-img convert: (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) print rcu_call_ready_event $4 =3D {value =3D 4294967295, initialized =3D true} value INT_MAX (4294967295) seems WRONG for qemu_futex_wait(): - EV_BUSY, being -1, and passed as an argument qemu_futex_wait(void *, unsigned), is a two's complement, making argument into a INT_MAX when that's not what is expected (unless I missed something). *** If that is the case, unsure if you, Paolo, prefer declaring *(QemuEvent)->value as an integer or changing EV_BUSY to "2" would okay here *** BUG: description: https://bugs.launchpad.net/qemu/+bug/1805256/comments/15 =3D=3D=3D=3D=3D=3D=3D=3D ISSUE #2 =3D=3D=3D=3D=3D=3D=3D=3D I found this when debugging lockups while in futex() in a specific ARM64 server - https://bugs.launchpad.net/qemu/+bug/1805256 - which I'm still investigating. After fixing the issue above, I'm still getting stuck into: qemu_event_wait() -> qemu_futex_wait() *** As if qemu_event_set() has ran before qemu_futex_wait() ever started running *** The Other threads are waiting for poll() on a PIPE coming from this stuck thread (thread #1), and in sigwait(): (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 QUESTION: - Should qemu_event_set() check return code from qemu_futex_wake()->qemu_futex()->syscall() in order to know if ANY waiter was ever woken up ? Maybe even loop until at least 1 is awaken ? Tks in advance, Rafael D. Tinoco -- = 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 Bug 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, = timeout=3D, timeout@entry=3D0x0, sigmask=3D0xffffc123b= 950) at ../sysdeps/unix/sysv/linux/ppoll.c:39 #1 0x0000aaaabbefaf00 in ppoll (__ss=3D0x0, __timeout=3D0x0, __nfds=3D, = __fds=3D) at /usr/include/aarch64-linux-gnu/bits/poll2= .h:77 #2 qemu_poll_ns (fds=3D, nfds=3D, = timeout=3Dtimeout@entry=3D-1) at util/qemu-timer.c:322 #3 0x0000aaaabbefbf80 in os_host_main_loop_wait (timeout=3D-1) at 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