Comment 11 for bug 1211700

The cursor moving actually is not interesting. Hardware cursor movement is a separate thread of the Mir server and drawn separately to the Mir server process. So the Mir compositor can be hung and the hardware cursor will keep moving smoothly.

Turns out my compositor thread is hung deep in the radeon code below eglSwapBuffers, which supports the idea that this is purely GPU flooding/starvation:

#0 pthread_cond_wait@@GLIBC_2.3.2 ()
    at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1 0x00007fffef2624ab in cnd_wait (mtx=0x7ffff7ebd1c8, cond=0x7ffff7ebd1f0)
    at ../../../../include/c11/threads_posix.h:159
#2 util_queue_job_wait (fence=fence@entry=0x7ffff7ebd1c8)
    at ../../../../src/gallium/auxiliary/util/u_queue.c:46
#3 0x00007fffef59770f in radeon_drm_cs_sync_flush (rcs=0x7ffff7e95010)
    at ../../../../../../src/gallium/winsys/radeon/drm/radeon_drm_cs.c:489
#4 radeon_drm_cs_flush (rcs=0x7ffff7e95010, flags=2, pfence=<optimised out>)
    at ../../../../../../src/gallium/winsys/radeon/drm/radeon_drm_cs.c:680
#5 0x00007fffef46cd47 in r600_context_gfx_flush (context=0x555555809b90,
    flags=2, fence=0x7fffe8c94838)
    at ../../../../../src/gallium/drivers/r600/r600_hw_context.c:283
#6 0x00007fffef5b666e in r600_flush_from_st (ctx=0x555555809b90,
    fence=0x7fffe8c948c0, flags=<optimised out>)
    at ../../../../../src/gallium/drivers/radeon/r600_pipe_common.c:357
#7 0x00007fffef0b513a in st_context_flush (stctxi=0x55555581f620, flags=2,
    fence=<optimised out>) at ../../../src/mesa/state_tracker/st_manager.c:506
#8 0x00007fffef1c860c in dri_flush (cPriv=<optimised out>,
    dPriv=<optimised out>, flags=<optimised out>, reason=<optimised out>)
    at ../../../../../src/gallium/state_trackers/dri/dri_drawable.c:532
#9 0x00007ffff4322714 in ?? ()
   from /usr/lib/x86_64-linux-gnu/mesa-egl/libEGL.so.1
#10 0x00007ffff4312faf in eglSwapBuffers ()
   from /usr/lib/x86_64-linux-gnu/mesa-egl/libEGL.so.1
#11 0x00007fffee5c18fb in mir::graphics::mesa::helpers::EGLHelper::swap_buffers
    (this=0x555555807e08)
    at /home/dan/bzr/mir/toy/src/platforms/mesa/server/display_helpers.cpp:402
#12 0x00007fffee5953b3 in mir::graphics::mesa::DisplayBuffer::swap_buffers (
    this=0x555555807d60)
    at /home/dan/bzr/mir/toy/src/platforms/mesa/server/kms/display_buffer.cpp:284
#13 0x00007ffff5e2bbbb in mir::renderer::gl::CurrentRenderTarget::swap_buffers
    (this=0x7fffe40008c8)
    at /home/dan/bzr/mir/toy/src/renderers/gl/renderer.cpp:75
#14 0x00007ffff5e2c878 in mir::renderer::gl::Renderer::render (
    this=0x7fffe40008c0,
    renderables=std::vector of length 2, capacity 2 = {...})
    at /home/dan/bzr/mir/toy/src/renderers/gl/renderer.cpp:217