Crash inside Unity IconLoader

[Thomi Richards]

I'm running unity from trunk under gdb. While running autopilot, unity crashed inside the IconLoader. Here's the stack trace:

#0 0x00007fffafde62e0 in ?? ()
#1 0x00007fffe6ae85a6 in ?? () from /usr/lib/x86_64-linux-gnu/libpixman-1.so.0
#2 0x00007fffe6b144f2 in ?? () from /usr/lib/x86_64-linux-gnu/libpixman-1.so.0
#3 0x00007fffe6aaf488 in pixman_image_composite32 () from /usr/lib/x86_64-linux-gnu/libpixman-1.so.0
#4 0x00007fffe6d5489d in ?? () from /usr/lib/x86_64-linux-gnu/libcairo.so.2
#5 0x00007fffe6d5630c in ?? () from /usr/lib/x86_64-linux-gnu/libcairo.so.2
#6 0x00007fffe6d5762b in ?? () from /usr/lib/x86_64-linux-gnu/libcairo.so.2
#7 0x00007fffe6d578a9 in ?? () from /usr/lib/x86_64-linux-gnu/libcairo.so.2
#8 0x00007fffe6d75704 in ?? () from /usr/lib/x86_64-linux-gnu/libcairo.so.2
#9 0x00007fffe6d4f3ed in ?? () from /usr/lib/x86_64-linux-gnu/libcairo.so.2
#10 0x00007fffe6d46290 in cairo_fill_preserve () from /usr/lib/x86_64-linux-gnu/libcairo.so.2
#11 0x00007fffe6d462a9 in cairo_fill () from /usr/lib/x86_64-linux-gnu/libcairo.so.2
#12 0x00007fffcbdf48a5 in ?? () from /usr/lib/x86_64-linux-gnu/librsvg-2.so.2
#13 0x00007fffcbdf12ca in ?? () from /usr/lib/x86_64-linux-gnu/librsvg-2.so.2
#14 0x00007fffcbde8cd3 in ?? () from /usr/lib/x86_64-linux-gnu/librsvg-2.so.2
#15 0x00007fffcbde90dc in ?? () from /usr/lib/x86_64-linux-gnu/librsvg-2.so.2
#16 0x00007fffcbde8cd3 in ?? () from /usr/lib/x86_64-linux-gnu/librsvg-2.so.2
#17 0x00007fffcbdf5478 in rsvg_handle_render_cairo_sub () from /usr/lib/x86_64-linux-gnu/librsvg-2.so.2
#18 0x00007fffcbdf5943 in rsvg_handle_get_pixbuf_sub () from /usr/lib/x86_64-linux-gnu/librsvg-2.so.2
#19 0x00007fffd806cd2b in ?? () from /usr/lib/x86_64-linux-gnu/gdk-pixbuf-2.0/2.10.0/loaders/libpixbufloader-svg.so
#20 0x00007fffe537b6f1 in gdk_pixbuf_loader_close () from /usr/lib/x86_64-linux-gnu/libgdk_pixbuf-2.0.so.0
#21 0x00007fffe53779f9 in ?? () from /usr/lib/x86_64-linux-gnu/libgdk_pixbuf-2.0.so.0
#22 0x00007fffe5379241 in gdk_pixbuf_new_from_stream_at_scale () from /usr/lib/x86_64-linux-gnu/libgdk_pixbuf-2.0.so.0
#23 0x00007fffe221a098 in ?? () from /usr/lib/x86_64-linux-gnu/libgtk-3.so.0
#24 0x00007fffe221cc72 in gtk_icon_info_load_icon () from /usr/lib/x86_64-linux-gnu/libgtk-3.so.0
#25 0x00007fffe34a3fb8 in unity::IconLoader::Impl::LoaderJobFunc (job=0xd8e6d70, canc=0x0, task=0x8ae80f0)
    at /home/thomi/code/canonical/unity/trunk/plugins/unityshell/src/IconLoader.cpp:468
#26 0x00007ffff1b7a12e in ?? () from /usr/lib/x86_64-linux-gnu/libgio-2.0.so.0
#27 0x00007ffff5bcb218 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#28 0x00007ffff5bca9b5 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#29 0x00007ffff703de9a in start_thread (arg=0x7fffafdf8700) at pthread_create.c:308
#30 0x00007ffff73454bd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#31 0x0000000000000000 in ?? ()

As you can see, the crash is deep within the pixbuf/svg/pixman libraries. At frame 25, everything seems normal enough:

#25 0x00007fffe34a3fb8 in unity::IconLoader::Impl::LoaderJobFunc (job=0xd8e6d70, canc=0x0, task=0x8ae80f0)
    at /home/thomi/code/canonical/unity/trunk/plugins/unityshell/src/IconLoader.cpp:468
468 task->result = gtk_icon_info_load_icon(task->icon_info, &task->error);
(gdb) l
463 IconLoaderTask *task)
464 {
465 // careful here this is running in non-main thread
466 if (task->icon_info)
467 {
468 task->result = gtk_icon_info_load_icon(task->icon_info, &task->error);
469
470 gtk_icon_info_free (task->icon_info);
471 task->icon_info = NULL;
472 }

(gdb) print task
$1 = (unity::IconLoader::Impl::IconLoaderTask *) 0x8ae80f0

(gdb) print task->icon_info
$4 = (GtkIconInfo *) 0x6dbd0c0

This comment from the source code:

// careful here this is running in non-main thread

...makes me suspect this is a threading issue. However, inspecting the running threads in gdb does not reveal anything enlightening (at least, not to me).