mirscreencast utility crashes on android devices

There is a subtle threading issue happening. For some unkown reason, the EGL context goes bad after waiting on a future in the main thread - the EGL context was made current in the main thread and should remain so.

Possibly a TLS issue.

....
 while (running)
    {
        //EGL context is good here - all gl calls made here work fine.
        frame_written_future.wait();
        //EGL context is not valid here anymore all gl calls fail after this wait
        auto format = read_pixels(frame_size, frame_data.data());
        frame_written_future = write_frame_to_file(frame_data, frame_number, format);

        egl_setup.swap_buffers();
        ++frame_number;
    }

Submitted an issue in libhybris:

https://github.com/libhybris/libhybris/issues/212

Fix committed into lp:mir/devel at revision None, scheduled for release in mir, milestone Unknown

Debugging further, I noticed that the gl android dispatcher table uses a fixed TLS slot ( slot 6 - offset #24 bytes).

The gnu linker/glibc libraries are not aware of this, so collisions can occur when using std::async or other c++11 constructs which uses thread local storage, which is why allocating dummy thread_local variables helps, since it pushes the slots used by std::async and others away from stomping over slot 6.

I don't think this can be solved in libhybris, short of rewriting the complete android gl dispatcher table.

This bug was fixed in the package mir - 0.1.6+14.04.20140310-0ubuntu1
---------------
mir (0.1.6+14.04.20140310-0ubuntu1) trusty; urgency=medium