[Bug 1831486] Re: qmp monitor deadlock (with spice events for ex)

[Thomas Huth]

This is an automated cleanup. This bug report has been moved to QEMU's
new bug tracker on gitlab.com and thus gets marked as 'expired' now.
Please continue with the discussion here:

 https://gitlab.com/qemu-project/qemu/-/issues/175


** Changed in: qemu
       Status: New => Expired

** Bug watch added: gitlab.com/qemu-project/qemu/-/issues #175
   https://gitlab.com/qemu-project/qemu/-/issues/175

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https://bugs.launchpad.net/bugs/1831486

Title:
  qmp monitor deadlock (with spice events for ex)

Status in QEMU:
  Expired

Bug description:
  If an event is emitted during monitor_flush_locked() it will deadlock.

  Thread 1 (Thread 0x7f14f1854000 (LWP 7245)):
  #0  0x00007f14fc30592d in __lll_lock_wait () at /lib64/libpthread.so.0
  #1  0x00007f14fc2fedc9 in pthread_mutex_lock () at /lib64/libpthread.so.0
  #2  0x000055de60e19327 in qemu_mutex_lock_impl (mutex=0x55de61859e58, 
file=0x55de60f1a640 "/home/elmarco/src/qq/monitor.c", line=438) at 
/home/elmarco/src/qq/util/qemu-thread-posix.c:66
  #3  0x000055de6085c5af in monitor_puts (mon=0x55de61859d30, 
str=0x55de62a61d30 "{\"timestamp\": {\"seconds\": 1559585795, \"microseconds\": 
508720}, \"event\": \"SPICE_DISCONNECTED\", \"data\": {\"server\": {\"port\": 
\"/tmp/.9IW52Z/spice.sock\", \"family\": \"unix\", \"host\": \"localhost\"}, 
\"client\": {"...) at /home/elmarco/src/qq/monitor.c:438
  #4  0x000055de6085c85a in qmp_send_response (mon=0x55de61859d30, 
rsp=0x55de61ed19a0) at /home/elmarco/src/qq/monitor.c:493
  #5  0x000055de6085c8ee in monitor_qapi_event_emit 
(event=QAPI_EVENT_SPICE_DISCONNECTED, qdict=0x55de61ed19a0) at 
/home/elmarco/src/qq/monitor.c:521
  #6  0x000055de6085c9ea in monitor_qapi_event_queue_no_reenter 
(event=QAPI_EVENT_SPICE_DISCONNECTED, qdict=0x55de61ed19a0) at 
/home/elmarco/src/qq/monitor.c:546
  #7  0x000055de6085cd7a in qapi_event_emit 
(event=QAPI_EVENT_SPICE_DISCONNECTED, qdict=0x55de61ed19a0) at 
/home/elmarco/src/qq/monitor.c:621
  #8  0x000055de60e04bc3 in qapi_event_send_spice_disconnected 
(server=0x55de61ee7b30, client=0x55de620c9090) at qapi/qapi-events-ui.c:101
  #9  0x000055de60c84381 in channel_event (event=3, info=0x55de6222f4c0) at 
/home/elmarco/src/qq/ui/spice-core.c:234
  #10 0x00007f14fc70ba3b in reds_handle_channel_event (reds=<optimized out>, 
event=3, info=0x55de6222f4c0) at reds.c:318
  #11 0x00007f14fc6f407b in main_dispatcher_self_handle_channel_event 
(info=0x55de6222f4c0, event=3, self=0x55de61a5b0b0) at main-dispatcher.c:191
  #12 0x00007f14fc6f407b in main_dispatcher_channel_event (self=0x55de61a5b0b0, 
event=event@entry=3, info=0x55de6222f4c0) at main-dispatcher.c:191
  #13 0x00007f14fc713cf3 in red_stream_push_channel_event 
(s=s@entry=0x55de6222f400, event=event@entry=3) at red-stream.c:416
  #14 0x00007f14fc713d2b in red_stream_free (s=0x55de6222f400) at 
red-stream.c:390
  #15 0x00007f14fc6fa67c in red_channel_client_finalize (object=0x55de62511360) 
at red-channel-client.c:347
  #16 0x00007f14fe4cfcf0 in g_object_unref () at /lib64/libgobject-2.0.so.0
  #17 0x00007f14fc6fca12 in red_channel_client_push (rcc=0x55de62511360) at 
red-channel-client.c:1340
  #18 0x00007f14fc6fca12 in red_channel_client_push (rcc=0x55de62511360) at 
red-channel-client.c:1303
  #19 0x00007f14fc6cd479 in red_char_device_send_msg_to_client 
(client=<optimized out>, msg=0x55de62512c00, dev=0x55de61a5b3b0) at 
char-device.c:307
  #20 0x00007f14fc6cd479 in red_char_device_send_msg_to_clients 
(msg=0x55de62512c00, dev=0x55de61a5b3b0) at char-device.c:307
  #21 0x00007f14fc6cd479 in red_char_device_read_from_device 
(dev=0x55de61a5b3b0) at char-device.c:355
  #22 0x000055de60a27dba in spice_chr_write (chr=0x55de61924c00, 
buf=0x55de6236c070 "{\"return\": {}, \"id\": 2}\r\n", len=25) at 
/home/elmarco/src/qq/chardev/spice.c:201
  #23 0x000055de60d89e29 in qemu_chr_write_buffer (s=0x55de61924c00, 
buf=0x55de6236c070 "{\"return\": {}, \"id\": 2}\r\n", len=25, 
offset=0x7ffcd5e1a860, write_all=false) at 
/home/elmarco/src/qq/chardev/char.c:113
  #24 0x000055de60d89f96 in qemu_chr_write (s=0x55de61924c00, 
buf=0x55de6236c070 "{\"return\": {}, \"id\": 2}\r\n", len=25, write_all=false) 
at /home/elmarco/src/qq/chardev/char.c:148
  #25 0x000055de60d8cf78 in qemu_chr_fe_write (be=0x55de61859d30, 
buf=0x55de6236c070 "{\"return\": {}, \"id\": 2}\r\n", len=25) at 
/home/elmarco/src/qq/chardev/char-fe.c:42
  #26 0x000055de6085c40f in monitor_flush_locked (mon=0x55de61859d30) at 
/home/elmarco/src/qq/monitor.c:404
  #27 0x000055de6085c614 in monitor_puts (mon=0x55de61859d30, 
str=0x55de622f6a40 "{\"return\": {}, \"id\": 2}\n") at 
/home/elmarco/src/qq/monitor.c:446
  #28 0x000055de6085c85a in qmp_send_response (mon=0x55de61859d30, 
rsp=0x55de61ecf960) at /home/elmarco/src/qq/monitor.c:493
  #29 0x000055de60865902 in monitor_qmp_respond (mon=0x55de61859d30, 
rsp=0x55de61ecf960) at /home/elmarco/src/qq/monitor.c:4128
  #30 0x000055de60865a19 in monitor_qmp_dispatch (mon=0x55de61859d30, 
req=0x55de622ec000) at /home/elmarco/src/qq/monitor.c:4157
  #31 0x000055de60865ce2 in monitor_qmp_bh_dispatcher (data=0x0) at 
/home/elmarco/src/qq/monitor.c:4224

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