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Bug 413032 - Locking issue with xcb in IA__gdk_display_sync
Locking issue with xcb in IA__gdk_display_sync
Status: RESOLVED FIXED
Product: gtk+
Classification: Platform
Component: Backend: X11
unspecified
Other Linux
: Normal critical
: ---
Assigned To: gtk-bugs
gtk-bugs
Depends on:
Blocks:
 
 
Reported: 2007-02-28 12:42 UTC by Sebastian Dröge (slomo)
Modified: 2007-03-09 05:33 UTC
See Also:
GNOME target: ---
GNOME version: ---


Description Sebastian Dröge (slomo) 2007-02-28 12:42:27 UTC 
Hi,
with latest gtk 2.10.9 and xcb 1.0 several gtk applications fail with a assertion in XCB's locking code:

xcb_xlib.c:41: xcb_xlib_lock: Assertion `!c->xlib.lock' failed.


Below I'll attach backtraces for xchat and epiphany showing this behaviour. All were produced by having a Gtk window unfocused and dragging some window from the wnck window applet to this window a few times.

nautilus and other's can be crashed the same way.

It wasn't always the application that was dragged or to which was dragged that crashed.

Bye
Comment 1 Sebastian Dröge (slomo) 2007-02-28 12:43:12 UTC 
xchat:

+ Trace 114601







Comment 2


Sebastian Dröge (slomo)





          2007-02-28 12:44:06 UTC
        



epiphany (Thread 1 crashed running the Gtk main loop... for both backtraces):






+
Trace
    114602






Thread 1
          (process 9902)


    

  • 
#0
__kernel_vsyscall

    • 

  • 
#1
raise

    
                from
                /lib/tls/i686/cmov/libc.so.6

    

    • 

  • 
#2
nsProfileLock::FatalSignalHandler

    
                at nsProfileLock.cpp
                  line
                  206

    

    • 

  • 
#3
<signal handler called>

    • 

  • 
#4
__kernel_vsyscall

    • 

  • 
#5
raise

    
                from
                /lib/tls/i686/cmov/libc.so.6

    

    • 

  • 
#6
abort

    
                from
                /lib/tls/i686/cmov/libc.so.6

    

    • 

  • 
#7
__assert_fail

    
                from
                /lib/tls/i686/cmov/libc.so.6

    

    • 

  • 
#8
xcb_xlib_lock

    
                from
                /usr/lib/libxcb-xlib.so.0

    

    • 

  • 
#9
_XCBLockDisplay

    
                at ../../src/xcb_lock.c
                  line
                  20

    

    • 

  • 
#10
XSync

    
                at ../../src/Sync.c
                  line
                  46

    

    • 

  • 
#11
IA__gdk_display_sync

    
                at gdkdisplay-x11.c
                  line
                  635

    

    • 

  • 
#12
xdnd_manage_source_filter

    
                at gdkdnd-x11.c
                  line
                  2595

    

    • 

  • 
#13
gdk_drag_context_finalize

    
                at gdkdnd-x11.c
                  line
                  184

    

    • 

  • 
#14
IA__g_object_unref

    
                at gobject.c
                  line
                  1788

    

    • 

  • 
#15
send_client_message_async_cb

    
                at gdkdnd-x11.c
                  line
                  2157

    

    • 

  • 
#16
send_event_handler

    
                at gdkasync.c
                  line
                  150

    

    • 

  • 
#17
process_responses

    
                at ../../src/xcb_io.c
                  line
                  98

    

    • 

  • 
#18
_XEventsQueued

    
                at ../../src/xcb_io.c
                  line
                  196

    

    • 

  • 
#19
XPending

    
                at ../../src/Pending.c
                  line
                  57

    

    • 

  • 
#20
gdk_check_xpending

    
                at gdkevents-x11.c
                  line
                  148

    

    • 

  • 
#21
gdk_event_check

    
                at gdkevents-x11.c
                  line
                  2292

    

    • 

  • 
#22
IA__g_main_context_check

    
                at gmain.c
                  line
                  2552

    

    • 

  • 
#23
g_main_context_iterate

    
                at gmain.c
                  line
                  2674

    

    • 

  • 
#24
IA__g_main_loop_run

    
                at gmain.c
                  line
                  2881

    

    • 

  • 
#25
IA__gtk_main

    
                at gtkmain.c
                  line
                  1171

    

    • 

  • 
#26
main

    • 













Comment 3


Sebastian Dröge (slomo)





          2007-02-28 12:48:18 UTC
        



Might be related to bug #353842 though this was with normal libX11... probably a deadlock while xcb just asserts for this.






Comment 4


Sebastian Dröge (slomo)





          2007-02-28 16:23:24 UTC
        



Also crashes gnome-panel under some situations, backtrace is different there though and one gets a segfault and no xcb assertions... but at the same time most of the time other apps, like xchat or epiphany for example, crash with the xcb assertion pasted above. Below is the gnome-panel backtrace:





+
Trace
    114656






Thread 1
          (process 7953)


    

  • 
#0
set_icon_stock_pixbuf

    
                at gtkdnd.c
                  line
                  3008

    

    • 

  • 
#1
IA__gtk_drag_set_icon_default

    
                at gtkdnd.c
                  line
                  3204

    

    • 

  • 
#2
wnck_drag_window_destroyed

    
                at pager.c
                  line
                  1472

    

    • 

  • 
#3
weak_refs_notify

    
                at gobject.c
                  line
                  1461

    

    • 

  • 
#4
IA__g_datalist_id_set_data_full

    
                at gdataset.c
                  line
                  242

    

    • 

  • 
#5
g_object_real_dispose

    
                at gobject.c
                  line
                  534

    

    • 

  • 
#6
IA__g_object_unref

    
                at gobject.c
                  line
                  1760

    

    • 

  • 
#7
_wnck_window_destroy

    
                at window.c
                  line
                  443

    

    • 

  • 
#8
do_update_now

    
                at screen.c
                  line
                  1414

    

    • 

  • 
#9
update_idle

    
                at screen.c
                  line
                  1936

    

    • 

  • 
#10
g_idle_dispatch

    
                at gmain.c
                  line
                  3928

    

    • 

  • 
#11
IA__g_main_context_dispatch

    
                at gmain.c
                  line
                  2045

    

    • 

  • 
#12
g_main_context_iterate

    
                at gmain.c
                  line
                  2677

    

    • 

  • 
#13
IA__g_main_loop_run

    
                at gmain.c
                  line
                  2881

    

    • 

  • 
#14
IA__gtk_main

    
                at gtkmain.c
                  line
                  1171

    

    • 

  • 
#15
main

    • 













Comment 5


Chris Rose





          2007-02-28 17:37:37 UTC
        



I can reproduce this also, if any other backtraces are needed.

Ubuntu bug: https://launchpad.net/ubuntu/+source/gtk+2.0/+bug/88608






Comment 6


Sebastian Dröge (slomo)





          2007-02-28 18:32:17 UTC
        



And also happens completely unmotivated, without moving the cursor or typing something. Just happend to me with epiphany...






Comment 7


Matthias Clasen





          2007-03-08 22:27:04 UTC
        



This turns out to be an incompatibility between traditional and xcb-ified
xlib wrt to some semi-internal apis. Old libX11 executed the async callbacks 
outside of the display lock, xcb does it inside the lock. Thus the we deadlock
as soon as the callback calls back into libX11.

Possible fixes:

- rewrite gdkasync.c to use xcb directly, rather than rely on the xcb-emulation
  of internal Xlib apis. This is quite a bit of work, and probably best undertaken
  in the context of an xcb backend for GDK.

- defer the callbacks to an idle.






Comment 8


Matthias Clasen





          2007-03-09 05:33:09 UTC
        



2007-03-08  Matthias Clasen <mclasen@redhat.com>

        * gdk/x11/gdkasync.c (send_event_handler): Defer the callbacks
        to an idle to avoid deadlock with xcb-ified libX11.  (#413032,
        Sebastian Dröge)