[Qemu-devel] [Bug 1805256] Re: qemu-img hangs on high core count ARM system

[dann frazier <dann.frazier@canonical.com>]

ext4 filesystem, SATA drive:

(gdb) thread apply all bt

Thread 3 (Thread 0xffff9bffc9a0 (LWP 9015)):
#0  0x0000ffffaaa462cc in __GI___sigtimedwait (set=<optimized out>, 
    set@entry=0xaaaae725c070, info=info@entry=0xffff9bffbf18, 
    timeout=0x3ff0000000000001, timeout@entry=0x0)
    at ../sysdeps/unix/sysv/linux/sigtimedwait.c:42
#1  0x0000ffffaab7dfac in __sigwait (set=set@entry=0xaaaae725c070, 
    sig=sig@entry=0xffff9bffbff4) at ../sysdeps/unix/sysv/linux/sigwait.c:28
#2  0x0000aaaad998a628 in sigwait_compat (opaque=0xaaaae725c070)
    at util/compatfd.c:36
#3  0x0000aaaad998bce0 in qemu_thread_start (args=<optimized out>)
    at util/qemu-thread-posix.c:498
#4  0x0000ffffaab73088 in start_thread (arg=0xffffc528531f)
    at pthread_create.c:463
#5  0x0000ffffaaae34ec in thread_start ()
    at ../sysdeps/unix/sysv/linux/aarch64/clone.S:78

Thread 2 (Thread 0xffffa0e779a0 (LWP 9014)):
#0  syscall () at ../sysdeps/unix/sysv/linux/aarch64/syscall.S:38
#1  0x0000aaaad998c9e8 in qemu_futex_wait (val=<optimized out>, f=<optimized out>)
    at /home/ubuntu/qemu/include/qemu/futex.h:29
#2  qemu_event_wait (ev=ev@entry=0xaaaad9a091c0 <rcu_call_ready_event>)
    at util/qemu-thread-posix.c:442
#3  0x0000aaaad99a6834 in call_rcu_thread (opaque=<optimized out>)
    at util/rcu.c:261
#4  0x0000aaaad998bce0 in qemu_thread_start (args=<optimized out>)
    at util/qemu-thread-posix.c:498
#5  0x0000ffffaab73088 in start_thread (arg=0xffffc528542f)
    at pthread_create.c:463
#6  0x0000ffffaaae34ec in thread_start ()
    at ../sysdeps/unix/sysv/linux/aarch64/clone.S:78

Thread 1 (Thread 0xffffa0fa8010 (LWP 9013)):
#0  0x0000ffffaaada154 in __GI_ppoll (fds=0xaaaae7291dc0, nfds=187650771816320, 
    timeout=<optimized out>, timeout@entry=0x0, sigmask=0xffffc52852e0)
    at ../sysdeps/unix/sysv/linux/ppoll.c:39
#1  0x0000aaaad9987f00 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  0x0000aaaad9988f80 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  0x0000aaaad98b7a30 in convert_do_copy (s=0xffffc52854e8) at qemu-img.c:1980
#6  img_convert (argc=<optimized out>, argv=<optimized out>) at qemu-img.c:2456
#7  0x0000aaaad98b033c in main (argc=7, argv=<optimized out>) at qemu-img.c:4975

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https://bugs.launchpad.net/bugs/1805256

Title:
  qemu-img hangs on high core count ARM system

Status in QEMU:
  New

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)

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