Mir clients freeze in advance_buffer if you Alt+Tab too much

[Daniel van Vugt]

TEST CASE:
1. Start mir_demo_server_shell
2. Start mir_demo_client_eglplasma
3. Start mir_demo_client_egltriangle
4. Alt+Tab slowly, making sure you can switch between clients.
5. Hold down Alt+Tab to switch rapidly.

Expected: Clients switch rapidly and keep running.
Observed: Clients switch rapidly but eventually freeze (stop rendering), one by one. The shell continues to respond to input, but once a client is frozen, it stays that way until restarted.

[Daniel van Vugt (vanvugt)]

The hang is predictably under swap buffers:

[Switching to thread 1 (Thread 0x7f4a09f2b780 (LWP 32448))]
#0 pthread_cond_wait@@GLIBC_2.3.2 ()
    at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
185 in ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S
#0 pthread_cond_wait@@GLIBC_2.3.2 ()
    at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1 0x00007f4a07ef21ec in std::condition_variable::wait(std::unique_lock<std::mutex>&) () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#2 0x00007f4a09a8aeb9 in MirWaitHandle::wait_for_all (this=0x14847d0)
    at /home/dan/bzr/mir/dev/src/client/mir_wait_handle.cpp:54
#3 0x00007f4a09a8249f in mir_wait_for (wait_handle=0x14847d0)
    at /home/dan/bzr/mir/dev/src/client/mir_client_library.cpp:367
#4 0x00007f4a09a7c612 in mir::client::gbm::GBMNativeSurface::advance_buffer (
    this=0x7f4a00001c50, buffer_package=0x7fff5d22c070)
    at /home/dan/bzr/mir/dev/src/client/gbm/gbm_native_surface.cpp:63
#5 0x00007f4a09a7c510 in (anonymous namespace)::advance_buffer_static (
    surface=0x7f4a00001c50, buffer_package=0x7fff5d22c070)
    at /home/dan/bzr/mir/dev/src/client/gbm/gbm_native_surface.cpp:31
#6 0x00007f4a0971b447 in mir_advance_colour_buffer (surf=<optimised out>,
    surf=<optimised out>)
    at ../../../../../../src/egl/drivers/dri2/platform_mir.c:139
#7 0x00007f4a0971b509 in dri2_swap_buffers (drv=<optimised out>,
    disp=<optimised out>, draw=0x14a1930)
    at ../../../../../../src/egl/drivers/dri2/platform_mir.c:265
#8 0x00007f4a0970d496 in eglSwapBuffers (dpy=0x14a0c70,
    surface=<optimised out>) at ../../../../../src/egl/main/eglapi.c:698
#9 0x0000000000401f4e in mir_eglapp_swap_buffers ()
    at /home/dan/bzr/mir/dev/examples/eglapp.c:80
#10 0x0000000000401e35 in main (argc=1, argv=0x7fff5d22d148)
    at /home/dan/bzr/mir/dev/examples/eglplasma.c:155

---

[Switching to thread 1 (Thread 0x7f1170e1b780 (LWP 32443))]
#0 pthread_cond_wait@@GLIBC_2.3.2 ()
    at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
185 in ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S
#0 pthread_cond_wait@@GLIBC_2.3.2 ()
    at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1 0x00007f116ede21ec in std::condition_variable::wait(std::unique_lock<std::mutex>&) () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#2 0x00007f117097aeb9 in MirWaitHandle::wait_for_all (this=0x7c27d0)
    at /home/dan/bzr/mir/dev/src/client/mir_wait_handle.cpp:54
#3 0x00007f117097249f in mir_wait_for (wait_handle=0x7c27d0)
    at /home/dan/bzr/mir/dev/src/client/mir_client_library.cpp:367
#4 0x00007f117096c612 in mir::client::gbm::GBMNativeSurface::advance_buffer (
    this=0x7f1168001c50, buffer_package=0x7fffcfc06750)
    at /home/dan/bzr/mir/dev/src/client/gbm/gbm_native_surface.cpp:63
#5 0x00007f117096c510 in (anonymous namespace)::advance_buffer_static (
    surface=0x7f1168001c50, buffer_package=0x7fffcfc06750)
    at /home/dan/bzr/mir/dev/src/client/gbm/gbm_native_surface.cpp:31
#6 0x00007f117060b447 in mir_advance_colour_buffer (surf=<optimised out>,
    surf=<optimised out>)
    at ../../../../../../src/egl/drivers/dri2/platform_mir.c:...

[Daniel van Vugt (vanvugt)]

Can't reproduce it now... !?

[kevin gunn (kgunn72)]

bug seems overcome by events, moving to invalid...reactivate if you can repro

[Daniel van Vugt (vanvugt)]

It was definitely a very bad bug when I was seeing it. I'd rather it expired naturally. "Invalid" means it's not a bug, which is untrue.

[Launchpad Janitor (janitor)]

[Expired for Mir because there has been no activity for 60 days.]