(gdb) bt
#0  0x00007f6ed83c286d in nanosleep () from /lib64/libpthread.so.0
#1  0x00007f6ed86269fe in SDL_Delay () from /lib64/libSDL-1.2.so.0
#2  0x00007f6ed86127de in X11_GrabInputNoLock () from /lib64/libSDL-1.2.so.0
#3  0x00007f6ed8612912 in X11_GrabInput () from /lib64/libSDL-1.2.so.0
#4  0x00007f6ed85fd077 in SDL_WM_GrabInputRaw () from /lib64/libSDL-1.2.so.0
#5  0x00007f6eda3f6396 in sdl_grab_start () at ui/sdl.c:387
#6  sdl_grab_start () at ui/sdl.c:371
#7  0x00007f6eda3f6485 in absolute_mouse_grab () at ui/sdl.c:407
#8  0x00007f6eda4f9874 in notifier_list_notify (list=list@entry=0x7f6edad0a8e0 <mouse_mode_notifiers>, data=data@entry=0x0) at util/notify.c:39
#9  0x00007f6eda3f39c8 in check_mode_change () at ui/input.c:341
#10 0x00007f6eda3f3d23 in qemu_activate_mouse_event_handler (entry=<optimized out>) at ui/input.c:375
#11 0x00007f6eda38c4ea in usb_wacom_poll (s=s@entry=0x7f6edc72baf0, buf=buf@entry=0x7f6edc72bbdc "\002\002\061", len=len@entry=2) at hw/usb/dev-wacom.c:213
#12 0x00007f6eda38c8e6 in usb_wacom_handle_control (index=<optimized out>, data=0x7f6edc72bbdc "\002\002\061", length=2, value=770, request=41217, p=0x7f6edc4f1160, dev=0x7f6edc72baf0) at hw/usb/dev-wacom.c:285
#13 usb_wacom_handle_control (dev=0x7f6edc72baf0, p=0x7f6edc4f1160, request=41217, value=770, index=<optimized out>, length=2, data=0x7f6edc72bbdc "\002\002\061") at hw/usb/dev-wacom.c:256
#14 0x00007f6eda380abe in do_token_setup (p=0x7f6edc4f1160, s=0x7f6edc72baf0) at hw/usb/core.c:119
#15 usb_process_one (p=0x7f6edc4f1160) at hw/usb/core.c:362
#16 0x00007f6eda380cc8 in usb_handle_packet (dev=<optimized out>, p=p@entry=0x7f6edc4f1160) at hw/usb/core.c:407
#17 0x00007f6eda395dbe in uhci_handle_td (s=s@entry=0x7f6edc4dd870, q=0x7f6edc8f25a0, q@entry=0x0, qh_addr=qh_addr@entry=10515490, td=td@entry=0x7fff85655d90, td_addr=<optimized out>,
    int_mask=int_mask@entry=0x7fff85655d7c) at hw/usb/hcd-uhci.c:897
#18 0x00007f6eda396301 in uhci_process_frame (s=s@entry=0x7f6edc4dd870) at hw/usb/hcd-uhci.c:1084
#19 0x00007f6eda396545 in uhci_frame_timer (opaque=0x7f6edc4dd870) at hw/usb/hcd-uhci.c:1183
#20 uhci_frame_timer (opaque=0x7f6edc4dd870) at hw/usb/hcd-uhci.c:1143
#21 0x00007f6eda3d351b in qemu_run_timers (clock=0x7f6edc042cd0) at qemu-timer.c:394
#22 qemu_run_timers (clock=0x7f6edc042cd0) at qemu-timer.c:375
#23 0x00007f6eda3d377e in qemu_run_all_timers () at qemu-timer.c:452
#24 0x00007f6eda3a5b8c in main_loop_wait (nonblocking=<optimized out>) at main-loop.c:470
#25 0x00007f6eda28b6d5 in main_loop () at vl.c:2029
#26 main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at vl.c:4419
(gdb)