Freezes in xcb_wait_for_reply64

[vfaronov]

Sometimes the Gunison UI just freezes for no apparent reason. This has happened to me a few times on Linux.

GDB backtrace at the time of freeze

#0  0x00007f8d614e3aff in __GI___poll (fds=0x7ffc40d00188, nfds=1, timeout=-1) at ../sysdeps/unix/sysv/linux/poll.c:29
#1  0x00007f8d60a86c1a in  () at /lib/x86_64-linux-gnu/libxcb.so.1
#2  0x00007f8d60a8861f in  () at /lib/x86_64-linux-gnu/libxcb.so.1
#3  0x00007f8d60a88796 in xcb_wait_for_reply64 () at /lib/x86_64-linux-gnu/libxcb.so.1
#4  0x00007f8d6117fee8 in _XReply () at /lib/x86_64-linux-gnu/libX11.so.6
#5  0x00007f8d6117b7f1 in XSync () at /lib/x86_64-linux-gnu/libX11.so.6
#6  0x00007f8d61856f86 in find_current_serial (xdisplay=0x2667f20) at ../../../../../gdk/x11/gdkgeometry-x11.c:107
#7  gdk_window_queue (new_item=0x2a0c110, window=0x2815c70 [GdkX11Window]) at ../../../../../gdk/x11/gdkgeometry-x11.c:167
#8  _gdk_x11_window_queue_antiexpose (window=0x2815c70 [GdkX11Window], area=<optimized out>) at ../../../../../gdk/x11/gdkgeometry-x11.c:224
#9  0x00007f8d618354a9 in gdk_window_process_updates_internal (window=0x2815c70 [GdkX11Window]) at ../../../../gdk/gdkwindow.c:4018
#10 0x00007f8d61835674 in gdk_window_process_updates_with_mode (recurse_mode=<optimized out>, window=<optimized out>) at ../../../../gdk/gdkwindow.c:4215
#11 gdk_window_process_updates_with_mode (window=<optimized out>, recurse_mode=<optimized out>) at ../../../../gdk/gdkwindow.c:4186
#12 0x00007f8d621d9a56 in _g_closure_invoke_va (closure=0x29502d0, return_value=0x0, instance=0x269e410, args=0x7ffc40d007a0, n_params=0, param_types=0x0)
    at ../../../gobject/gclosure.c:873
#13 0x00007f8d621f8b48 in g_signal_emit_valist (instance=0x269e410, signal_id=<optimized out>, detail=0, var_args=var_args@entry=0x7ffc40d007a0)
    at ../../../gobject/gsignal.c:3408
#14 0x00007f8d621f90f3 in g_signal_emit (instance=instance@entry=0x269e410, signal_id=<optimized out>, detail=detail@entry=0)
    at ../../../gobject/gsignal.c:3555
#15 0x00007f8d6182c3b3 in _gdk_frame_clock_emit_paint (frame_clock=frame_clock@entry=0x269e410 [GdkFrameClockIdle]) at ../../../../gdk/gdkframeclock.c:643
#16 0x00007f8d6182ccf3 in gdk_frame_clock_paint_idle (data=0x269e410) at ../../../../gdk/gdkframeclockidle.c:450
#17 0x00007f8d61816f4d in gdk_threads_dispatch (data=0x2a10400, data@entry=<error reading variable: value has been optimized out>)
    at ../../../../gdk/gdk.c:769
#18 0x00007f8d620eebe8 in g_timeout_dispatch (source=0x2a13d10, callback=<optimized out>, user_data=<optimized out>) at ../../../glib/gmain.c:4800
#19 0x00007f8d620ee04e in g_main_dispatch (context=0x268f9b0) at ../../../glib/gmain.c:3309
#20 g_main_context_dispatch (context=context@entry=0x268f9b0) at ../../../glib/gmain.c:3974
#21 0x00007f8d620ee400 in g_main_context_iterate (context=0x268f9b0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>)
    at ../../../glib/gmain.c:4047
#22 0x00007f8d620ee6f3 in g_main_loop_run (loop=0x2a604b0) at ../../../glib/gmain.c:4241
#23 0x00007f8d61b3937d in gtk_main () at ../../../../gtk/gtkmain.c:1328
#24 0x00000000004eb7f0 in runtime.asmcgocall () at /home/vasiliy/cur/ware/go/1.16/src/runtime/asm_amd64.s:667
#25 0x000000c000010530 in  ()
#26 0x000000000085cfa0 in runtime.m0 ()
#27 0x000000c00013ddd8 in  ()
#28 0x0000000000000001 in  ()
#29 0x000000c00013dde8 in  ()
#30 0x0000000000000120 in  ()
#31 0x000000c000000180 in  ()
#32 0x000000001adfcbda in  ()
#33 0x00000000004bcb80 in runtime.mstart () at /home/vasiliy/cur/ware/go/1.16/src/runtime/signal_unix.go:1035
#34 0x00000000004e9c14 in runtime.rt0_go () at /home/vasiliy/cur/ware/go/1.16/src/runtime/asm_amd64.s:226
#35 0x0000000000000000 in  ()

Go backtrace (on SIGQUIT)

PC=0x7f8d614e3aff m=0 sigcode=0
signal arrived during cgo execution
goroutine 1 [syscall, 3 minutes, locked to thread]:
runtime.cgocall(0x60aa40, 0xc000431f50, 0x0)
        /home/vasiliy/cur/ware/go/1.16/src/runtime/cgocall.go:154 +0x5b fp=0xc000431f20 sp=0xc000431ee8 pc=0x485c3b
github.com/gotk3/gotk3/gtk._Cfunc_gtk_main()
        _cgo_gotypes.go:17384 +0x3c fp=0xc000431f50 sp=0xc000431f20 pc=0x5a549c
github.com/gotk3/gotk3/gtk.Main(...)
        /home/vasiliy/.cache/gopath/pkg/mod/github.com/gotk3/[email protected]/gtk/gtk.go:1241
main.main()
        /home/vasiliy/cur/gunison/gunison/main.go:86 +0xf6 fp=0xc000431f88 sp=0xc000431f50 pc=0x5e5396
runtime.main()
        /home/vasiliy/cur/ware/go/1.16/src/runtime/proc.go:225 +0x256 fp=0xc000431fe0 sp=0xc000431f88 pc=0x4ba0f6
runtime.goexit()
        /home/vasiliy/cur/ware/go/1.16/src/runtime/asm_amd64.s:1371 +0x1 fp=0xc000431fe8 sp=0xc000431fe0 pc=0x4ebb81
goroutine 6 [IO wait, 3 minutes]:
internal/poll.runtime_pollWait(0x7f8d3872ca48, 0x72, 0xffffffffffffffff)
        /home/vasiliy/cur/ware/go/1.16/src/runtime/netpoll.go:222 +0x55
internal/poll.(*pollDesc).wait(0xc000067098, 0x72, 0x10001, 0x10000, 0xffffffffffffffff)
        /home/vasiliy/cur/ware/go/1.16/src/internal/poll/fd_poll_runtime.go:87 +0x45
internal/poll.(*pollDesc).waitRead(...)
        /home/vasiliy/cur/ware/go/1.16/src/internal/poll/fd_poll_runtime.go:92
internal/poll.(*FD).Read(0xc000067080, 0xc00008e000, 0x10000, 0x10000, 0x0, 0x0, 0x0)
        /home/vasiliy/cur/ware/go/1.16/src/internal/poll/fd_unix.go:166 +0x1d5
os.(*File).read(...)
        /home/vasiliy/cur/ware/go/1.16/src/os/file_posix.go:31
os.(*File).Read(0xc000010518, 0xc00008e000, 0x10000, 0x10000, 0x3, 0x0, 0x0)
        /home/vasiliy/cur/ware/go/1.16/src/os/file.go:117 +0x77
main.watchUnison()
        /home/vasiliy/cur/gunison/gunison/main.go:126 +0x8b
created by main.startUnison
        /home/vasiliy/cur/gunison/gunison/main.go:119 +0x4bf
rax    0xfffffffffffffffc
rbx    0x2669180
rcx    0x7f8d614e3aff
rdx    0xffffffff
rdi    0x7ffc40d00188
rsi    0x1
rbp    0x0
rsp    0x7ffc40d00150
r8     0x0
r9     0x7f8d615b9b80
r10    0x7
r11    0x293
r12    0x7ffc40d002a0
r13    0x0
r14    0x2669198
r15    0x7ffc40d00188
rip    0x7f8d614e3aff
rflags 0x293
cs     0x33
fs     0x0
gs     0x0

I also had one lock-up on Windows, which obviously must have had some other cause, but I didn’t get a backtrace.