From: Rafael David Tinoco <rafaeldtinoco@ubuntu.com> To: Paolo Bonzini <pbonzini@redhat.com> Cc: Bug 1805256 <1805256@bugs.launchpad.net>, QEMU Developers - ARM <qemu-arm@nongnu.org>, QEMU Developers <qemu-devel@nongnu.org> Subject: [Qemu-devel] qemu_futex_wait() lockups in ARM64: 2 possible issues Date: Tue, 10 Sep 2019 23:15:00 -0300 [thread overview] Message-ID: <cbe46ad6-ef6c-d155-e79a-672182c725ad@ubuntu.com> (raw) 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 <rcu_call_ready_event>) #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 <rcu_call_ready_event>) #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
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From: Rafael David Tinoco <rafaeldtinoco@kernelpath.com> To: qemu-devel@nongnu.org Subject: [Qemu-devel] [Bug 1805256] qemu_futex_wait() lockups in ARM64: 2 possible issues Date: Wed, 11 Sep 2019 02:15:00 -0000 [thread overview] Message-ID: <cbe46ad6-ef6c-d155-e79a-672182c725ad@ubuntu.com> (raw) Message-ID: <20190911021500.TfpxfkCK7Tz0gt8F42I0ZKHO2C-jnpk7YiOhTf4GeSM@z> (raw) In-Reply-To: 154327283728.15443.11625169757714443608.malonedeb@soybean.canonical.com 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 <rcu_call_ready_event>) #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 <rcu_call_ready_event>) #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=0xaaaae8a67dc0, nfds=187650274213760, timeout=<optimized out>, timeout@entry=0x0, sigmask=0xffffc123b950) at ../sysdeps/unix/sysv/linux/ppoll.c:39 #1 0x0000aaaabbefaf00 in ppoll (__ss=0x0, __timeout=0x0, __nfds=<optimized out>, __fds=<optimized out>) at /usr/include/aarch64-linux-gnu/bits/poll2.h:77 #2 qemu_poll_ns (fds=<optimized out>, nfds=<optimized out>, timeout=timeout@entry=-1) at util/qemu-timer.c:322 #3 0x0000aaaabbefbf80 in os_host_main_loop_wait (timeout=-1) at util/main-loop.c:233 #4 main_loop_wait (nonblocking=<optimized out>) at util/main-loop.c:497 #5 0x0000aaaabbe2aa30 in convert_do_copy (s=0xffffc123bb58) at qemu-img.c:1980 #6 img_convert (argc=<optimized out>, argv=<optimized out>) at qemu-img.c:2456 #7 0x0000aaaabbe2333c in main (argc=7, argv=<optimized out>) 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
next prev reply other threads:[~2019-09-11 2:17 UTC|newest] Thread overview: 141+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-11-26 22:53 [Qemu-devel] [Bug 1805256] [NEW] qemu-img hangs on high core count ARM system dann frazier 2018-11-26 23:26 ` [Qemu-devel] [Bug 1805256] " John Snow 2018-11-26 23:54 ` dann frazier 2018-12-05 11:20 ` Alex Bennée 2019-04-15 12:59 ` 贞贵李 2019-04-15 12:59 ` 贞贵李 2019-04-15 14:37 ` 贞贵李 2019-04-15 14:37 ` 贞贵李 2019-04-15 22:25 ` dann frazier 2019-04-15 22:25 ` dann frazier 2019-04-15 23:37 ` dann frazier 2019-04-15 23:37 ` dann frazier 2019-04-16 8:16 ` 贞贵李 2019-04-16 8:16 ` 贞贵李 2019-04-16 13:32 ` 贞贵李 2019-04-16 13:32 ` 贞贵李 2019-04-23 1:29 ` 贞贵李 2019-04-23 1:29 ` 贞贵李 2019-06-05 16:16 ` dann frazier 2019-09-05 15:03 ` Rafael David Tinoco 2019-09-06 15:12 ` Rafael David Tinoco 2019-09-06 15:16 ` Rafael David Tinoco 2019-09-06 21:22 ` Rafael David Tinoco 2019-09-09 16:47 ` Rafael David Tinoco 2019-09-10 2:04 ` Rafael David Tinoco 2019-09-10 14:16 ` Rafael David Tinoco 2019-09-10 18:15 ` [Qemu-devel] [Bug 1805256] Re: qemu-img hangs on rcu_call_ready_event logic in Aarch64 when converting images Rafael David Tinoco 2019-09-10 22:56 ` Rafael David Tinoco 2019-09-11 2:15 ` Rafael David Tinoco [this message] 2019-09-11 2:15 ` [Qemu-devel] [Bug 1805256] qemu_futex_wait() lockups in ARM64: 2 possible issues Rafael David Tinoco 2019-09-11 7:05 ` [Qemu-devel] " Rafael David Tinoco 2019-09-11 7:05 ` [Qemu-devel] [Bug 1805256] " Rafael David Tinoco 2019-09-11 13:17 ` [Qemu-devel] " Paolo Bonzini 2019-09-11 14:48 ` Rafael David Tinoco 2019-09-11 19:09 ` Rafael David Tinoco 2019-09-11 19:09 ` [Qemu-devel] [Bug 1805256] " Rafael David Tinoco 2019-09-24 20:25 ` [Qemu-devel] " dann frazier 2019-09-24 20:25 ` [Bug 1805256] " dann frazier 2019-10-02 9:23 ` Jan Glauber 2019-10-02 9:23 ` Jan Glauber 2019-10-02 9:45 ` Paolo Bonzini 2019-10-02 11:05 ` Jan Glauber 2019-10-02 11:05 ` [Bug 1805256] " Jan Glauber 2019-10-02 13:20 ` memory barriers and ATOMIC_SEQ_CST on aarch64 (was Re: [Qemu-devel] qemu_futex_wait() lockups in ARM64: 2 possible issues) Paolo Bonzini 2019-10-02 14:58 ` Torvald Riegel 2019-10-02 16:30 ` Paolo Bonzini 2019-10-07 11:06 ` [Qemu-devel] qemu_futex_wait() lockups in ARM64: 2 possible issues Paolo Bonzini 2019-10-07 14:36 ` Jan Glauber 2019-10-07 14:36 ` [Bug 1805256] " Jan Glauber 2019-10-07 14:44 ` dann frazier 2019-10-07 14:44 ` [Bug 1805256] " dann frazier 2019-10-07 14:58 ` Paolo Bonzini 2019-10-09 8:02 ` Jan Glauber 2019-10-09 8:02 ` [Bug 1805256] " Jan Glauber 2019-10-09 9:15 ` Paolo Bonzini 2019-10-11 6:05 ` Jan Glauber 2019-10-11 6:05 ` [Bug 1805256] " Jan Glauber 2019-10-11 8:18 ` Paolo Bonzini 2019-10-11 8:30 ` Jan Glauber 2019-10-11 8:30 ` [Bug 1805256] " Jan Glauber 2019-10-11 17:55 ` dann frazier 2019-10-11 17:55 ` dann frazier 2019-10-12 0:24 ` [Bug 1805256] " no-reply 2019-10-12 0:49 ` no-reply 2019-10-11 17:50 ` dann frazier 2019-10-11 17:50 ` [Bug 1805256] " dann frazier 2019-09-11 2:17 ` [Qemu-devel] [Bug 1805256] Re: qemu-img hangs on rcu_call_ready_event logic in Aarch64 when converting images Rafael David Tinoco 2019-09-11 11:19 ` Rafael David Tinoco 2019-09-11 19:23 ` Rafael David Tinoco 2019-10-02 11:02 ` Jan Glauber 2019-10-03 12:28 ` Rafael David Tinoco 2019-10-03 12:29 ` Rafael David Tinoco 2019-10-03 12:29 ` Rafael David Tinoco 2019-10-03 21:35 ` dann frazier 2019-12-13 14:24 ` dann frazier 2019-12-17 1:34 ` Fred Kimmy 2019-12-17 19:17 ` dann frazier 2019-12-18 2:40 ` Rafael David Tinoco 2019-12-18 9:52 ` iveskim 2019-12-18 14:52 ` dann frazier 2019-12-18 16:21 ` Ubuntu Foundations Team Bug Bot 2020-02-13 8:41 ` Ike Panhc 2020-02-13 8:42 ` Andrew Cloke 2020-02-13 9:20 ` Fred Kimmy 2020-04-15 2:47 ` Rafael David Tinoco 2020-05-04 7:24 ` Ike Panhc 2020-05-05 0:54 ` Ike Panhc 2020-05-05 1:22 ` Ying Fang 2020-05-05 6:15 ` Ike Panhc 2020-05-05 15:01 ` Ike Panhc 2020-05-05 18:48 ` Rafael David Tinoco 2020-05-05 23:55 ` dann frazier 2020-05-06 13:08 ` Rafael David Tinoco 2020-05-06 13:23 ` Rafael David Tinoco 2020-05-06 15:45 ` Ike Panhc 2020-05-06 16:42 ` dann frazier 2020-05-06 19:04 ` Launchpad Bug Tracker 2020-05-06 19:09 ` Philippe Mathieu-Daudé 2020-05-06 19:57 ` dann frazier 2020-05-06 20:11 ` Rafael David Tinoco 2020-05-06 21:10 ` Launchpad Bug Tracker 2020-05-06 21:44 ` Launchpad Bug Tracker 2020-05-07 3:37 ` Launchpad Bug Tracker 2020-05-07 7:00 ` Ike Panhc 2020-05-07 22:27 ` dann frazier 2020-05-14 8:05 ` Andrew Cloke 2020-05-27 4:55 ` Christian Ehrhardt 2020-05-28 14:58 ` Christian Ehrhardt 2020-05-29 7:55 ` Launchpad Bug Tracker 2020-05-29 8:01 ` Christian Ehrhardt 2020-06-02 22:45 ` Brian Murray 2020-06-02 22:49 ` [Bug 1805256] Please test proposed package Brian Murray 2020-06-02 22:54 ` Brian Murray 2020-06-03 4:09 ` [Bug 1805256] Autopkgtest regression report (qemu/1:4.0+dfsg-0ubuntu9.7) Ubuntu SRU Bot 2020-06-03 6:35 ` [Bug 1805256] Re: qemu-img hangs on rcu_call_ready_event logic in Aarch64 when converting images Ike Panhc 2020-06-03 8:40 ` [Bug 1805256] Autopkgtest regression report (qemu/1:4.2-3ubuntu6.2) Ubuntu SRU Bot 2020-06-05 3:51 ` [Bug 1805256] Re: qemu-img hangs on rcu_call_ready_event logic in Aarch64 when converting images Christian Ehrhardt 2020-06-11 8:04 ` Andrew Cloke 2020-06-17 5:16 ` Christian Ehrhardt 2020-06-18 9:23 ` Launchpad Bug Tracker 2020-06-18 9:23 ` [Bug 1805256] Update Released Łukasz Zemczak 2020-06-18 9:38 ` [Bug 1805256] Re: qemu-img hangs on rcu_call_ready_event logic in Aarch64 when converting images Launchpad Bug Tracker 2020-06-18 9:39 ` Launchpad Bug Tracker 2020-06-18 10:27 ` Andrew Cloke 2020-06-30 6:54 ` Christian Ehrhardt 2020-07-01 7:01 ` Ike Panhc 2020-07-12 13:16 ` Rafael David Tinoco 2020-07-13 3:59 ` Launchpad Bug Tracker 2020-07-13 4:12 ` Rafael David Tinoco 2020-07-15 15:31 ` dann frazier 2020-07-20 12:22 ` Rafael David Tinoco 2020-07-21 20:02 ` Rafael David Tinoco 2020-07-21 20:03 ` Rafael David Tinoco 2020-07-31 18:51 ` Rafael David Tinoco 2020-07-31 21:42 ` Rafael David Tinoco 2020-08-07 9:53 ` Timo Aaltonen 2020-08-07 14:41 ` [Bug 1805256] Autopkgtest regression report (qemu/1:2.11+dfsg-1ubuntu7.30) Ubuntu SRU Bot 2020-08-07 20:13 ` [Bug 1805256] Re: qemu-img hangs on rcu_call_ready_event logic in Aarch64 when converting images dann frazier 2020-08-14 19:49 ` dann frazier 2020-08-19 16:36 ` Launchpad Bug Tracker 2020-08-19 17:16 ` Andrew Cloke
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