When a monitor is connected to a Spice chardev, the monitor cleanup can dead-lock: #0 0x00007f43446637fd in __lll_lock_wait () at /lib64/libpthread.so.0 #1 0x00007f434465ccf4 in pthread_mutex_lock () at /lib64/libpthread.so.0 #2 0x0000556dd79f22ba in qemu_mutex_lock_impl (mutex=0x556dd81c9220 <monitor_lock>, file=0x556dd7ae3648 "/home/elmarco/src/qq/monitor.c", line=645) at /home/elmarco/src/qq/util/qemu-thread-posix.c:66 #3 0x0000556dd7431bd5 in monitor_qapi_event_queue (event=QAPI_EVENT_SPICE_DISCONNECTED, qdict=0x556dd9abc850, errp=0x7fffb7bbddd8) at /home/elmarco/src/qq/monitor.c:645 #4 0x0000556dd79d476b in qapi_event_send_spice_disconnected (server=0x556dd98ee760, client=0x556ddaaa8560, errp=0x556dd82180d0 <error_abort>) at qapi/qapi-events-ui.c:149 #5 0x0000556dd7870fc1 in channel_event (event=3, info=0x556ddad1b590) at /home/elmarco/src/qq/ui/spice-core.c:235 #6 0x00007f434560a6bb in reds_handle_channel_event (reds=<optimized out>, event=3, info=0x556ddad1b590) at reds.c:316 #7 0x00007f43455f393b in main_dispatcher_self_handle_channel_event (info=0x556ddad1b590, event=3, self=0x556dd9a7d8c0) at main-dispatcher.c:197 qemu#8 0x00007f43455f393b in main_dispatcher_channel_event (self=0x556dd9a7d8c0, event=event@entry=3, info=0x556ddad1b590) at main-dispatcher.c:197 qemu#9 0x00007f4345612833 in red_stream_push_channel_event (s=s@entry=0x556ddae2ef40, event=event@entry=3) at red-stream.c:414 qemu#10 0x00007f434561286b in red_stream_free (s=0x556ddae2ef40) at red-stream.c:388 qemu#11 0x00007f43455f9ddc in red_channel_client_finalize (object=0x556dd9bb21a0) at red-channel-client.c:347 qemu#12 0x00007f434b5f9fb9 in g_object_unref () at /lib64/libgobject-2.0.so.0 qemu#13 0x00007f43455fc212 in red_channel_client_push (rcc=0x556dd9bb21a0) at red-channel-client.c:1341 qemu#14 0x0000556dd76081ba in spice_port_set_fe_open (chr=0x556dd9925e20, fe_open=0) at /home/elmarco/src/qq/chardev/spice.c:241 qemu#15 0x0000556dd796d74a in qemu_chr_fe_set_open (be=0x556dd9a37c00, fe_open=0) at /home/elmarco/src/qq/chardev/char-fe.c:340 qemu#16 0x0000556dd796d4d9 in qemu_chr_fe_set_handlers (b=0x556dd9a37c00, fd_can_read=0x0, fd_read=0x0, fd_event=0x0, be_change=0x0, opaque=0x0, context=0x0, set_open=true) at /home/elmarco/src/qq/chardev/char-fe.c:280 qemu#17 0x0000556dd796d359 in qemu_chr_fe_deinit (b=0x556dd9a37c00, del=false) at /home/elmarco/src/qq/chardev/char-fe.c:233 qemu#18 0x0000556dd7432240 in monitor_data_destroy (mon=0x556dd9a37c00) at /home/elmarco/src/qq/monitor.c:786 qemu#19 0x0000556dd743b968 in monitor_cleanup () at /home/elmarco/src/qq/monitor.c:4683 qemu#20 0x0000556dd75ce776 in main (argc=3, argv=0x7fffb7bbe458, envp=0x7fffb7bbe478) at /home/elmarco/src/qq/vl.c:4660 Because spice code tries to emit a "disconnected" signal on the monitors. Fix this dead-lock by releasing the monitor lock for flush/destroy. monitor_lock protects mon_list, monitor_qapi_event_state and monitor_destroyed. monitor_flush() and monitor_data_destroy() don't access any of those variables. monitor_cleanup()'s loop is safe because it uses QTAILQ_FOREACH_SAFE(), and no further monitor can be added after calling monitor_cleanup() thanks to monitor_destroyed check in monitor_list_append(). Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Message-Id: <20181205203737.9011-8-marcandre.lureau@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>

R5900 system mode emulation #6

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