Bug 741042 – Segfault in wayland move drag after drag is unset

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Bug 741042 - Segfault in wayland move drag after drag is unset


Summary:	Segfault in wayland move drag after drag is unset


Status:	RESOLVED OBSOLETE

Product:	gtk+
Classification:	Platform
Component:	Backend: Wayland
Version:	3.14.x
Hardware:	Other Linux

Importance:	Normal normal
Target Milestone:	---
Assigned To:	gtk-bugs
QA Contact:	gtk-bugs

URL:
Whiteboard:

Depends on:
Blocks:

Reported:	2014-12-02 19:55 UTC by Jonny Lamb
Modified:	2015-11-17 20:40 UTC

See Also:
GNOME target:	---
GNOME version:	---

Attachments
workaround for crasher (435 bytes, patch) 2014-12-03 14:20 UTC, Jonny Lamb	none	Details \| Review

Description Jonny Lamb 2014-12-02 19:55:37 UTC

bug #731380 fixed some problems with touch events but now move drag segfaults, specifically because of 29d9b2f7cfec936b3a923797ac.

(sorry for the lack of debug symbols. not sure why they're not showing, the library is not stripped)

+ Trace 234392

#0 touch_handle_motion
from /usr/lib/libgdk-3.so.0
#1 ffi_call_SYSV
at ../src/arm/sysv.S line 196
#2 ffi_call
at ../src/arm/ffi.c line 250
#3 wl_closure_invoke
at src/connection.c line 934
#4 dispatch_event
at src/wayland-client.c line 1136
#5 dispatch_queue
at src/wayland-client.c line 1261
#6 wl_display_dispatch_queue
at src/wayland-client.c line 1445
#7 _gdk_wayland_display_queue_events
from /usr/lib/libgdk-3.so.0
#8 gdk_display_get_event
from /usr/lib/libgdk-3.so.0
#9 gdk_event_source_dispatch
from /usr/lib/libgdk-3.so.0
#10 g_main_dispatch
at gmain.c line 3064
#11 g_main_context_dispatch
at gmain.c line 3663
#12 g_main_context_iterate
at gmain.c line 3734
#13 g_main_context_iterate
at gmain.c line 3671
#14 g_main_context_iteration
at gmain.c line 3795
#15 g_application_run
at gapplication.c line 2282
#16 main
#0 gdk_wayland_device_unset_touch_grab
from /usr/lib/libgdk-3.so.0
#1 gdk_wayland_window_begin_move_drag
from /usr/lib/libgdk-3.so.0
#2 gdk_window_begin_move_drag_for_device
from /usr/lib/libgdk-3.so.0
#3 multipress_gesture_stopped_cb
from /usr/lib/libgtk-3.so.0
#4 g_cclosure_marshal_VOID__VOIDv
at gmarshal.c line 115
#5 _g_closure_invoke_va
at gclosure.c line 831
#6 g_signal_emit_valist
at gsignal.c line 3218
#7 g_signal_emit
at gsignal.c line 3365
#8 _gtk_gesture_multi_press_stop
from /usr/lib/libgtk-3.so.0
#9 _double_click_timeout_cb
from /usr/lib/libgtk-3.so.0
#10 gdk_threads_dispatch
from /usr/lib/libgdk-3.so.0
#11 g_timeout_dispatch
at gmain.c line 4473
#12 g_main_dispatch
at gmain.c line 3064
#13 g_main_context_dispatch
at gmain.c line 3663
#14 g_main_context_iterate
at gmain.c line 3734
#15 g_main_context_iterate
at gmain.c line 3671
#16 g_main_context_iteration
at gmain.c line 3795
#17 g_application_run
at gapplication.c line 2282
#18 main


I don't really understand why gdk_wayland_device_unset_touch_grab() is being called here but it was explicitly added in the aforementioned commit. Perhaps the fix here is just to ignore the motion event if we don't have a GdkWaylandTouchData (which doesn't appear to cause other issues)?

I don't know enough about this touch stack so I thought I'd just open a bug.

Comment 1 Jonny Lamb 2014-12-02 19:56:59 UTC

(the two backtraces come out badly in bugzilla. click the link to see both separately and with my comment in the middle.)

Comment 2 Jonny Lamb 2014-12-03 14:20:35 UTC

Created attachment 292071 [details] [review]
workaround for crasher

This stops the crash from happening and doesn't seem such a bad fix, but I could be wrong.

Comment 3 Matthias Clasen 2015-11-17 20:40:13 UTC

Can't reproduce a move drag with my touchscreen in a wayland session, so this is probably no longer relevant. Please reopen if it is.