x11: shutdown deadlock when X window closed

[Saviq]

This may well be a separate shutdown issue that just gets surfaced through this fix.

Here's another deadlock I've found - just close (×, or Alt+F4) the X window when GLMark2 is running.

$ ./bin/mir_performance_tests --gtest_filter=Hosted*
LD_LIBRARY_PATH=./build-Debug/bin/../lib/
MIR_SERVER_PLATFORM_PATH=./build-Debug/bin/../lib/server-modules/
exec=./build-Debug/bin/mir_performance_tests.bin
Running main() from main.cpp
Note: Google Test filter = Hosted*
[==========] Running 2 tests from 1 test suite.
[----------] Global test environment set-up.
[----------] 2 tests from HostedGLMark2Wayland
[ RUN      ] HostedGLMark2Wayland.fullscreen
Saving host output to: /tmp/HostedGLMark2Wayland_fullscreen_host.log
Saving server logs to: /tmp/HostedGLMark2Wayland_fullscreen_server.log
Saving GLMark2 detailed results to: /tmp/HostedGLMark2Wayland_fullscreen.log
^C
[1]    335565 killed     ./build-Debug/bin/mir_performance_tests --gtest_filter=Hosted*

Originally posted by @Saviq in #3030 (comment)

[AlanGriffiths]

I don't think the log with ^c matches the description "close (×, or Alt+F4) the X window"?

The log I get from closing the X window is:

$ cmake-build-release/bin/mir_performance_tests --gtest_filter=Hosted*
LD_LIBRARY_PATH=cmake-build-release/bin/../lib/
MIR_SERVER_PLATFORM_PATH=cmake-build-release/bin/../lib/server-modules/
exec=cmake-build-release/bin/mir_performance_tests.bin
Running main() from main.cpp
Note: Google Test filter = Hosted*
[==========] Running 2 tests from 1 test suite.
[----------] Global test environment set-up.
[----------] 2 tests from HostedGLMark2Wayland
[ RUN      ] HostedGLMark2Wayland.fullscreen
Saving host output to: /tmp/HostedGLMark2Wayland_fullscreen_host.log
Saving server logs to: /tmp/HostedGLMark2Wayland_fullscreen_server.log
Saving GLMark2 detailed results to: /tmp/HostedGLMark2Wayland_fullscreen.log
Mir fatal error: Critical error in Wayland platform: /home/alan/CLionProjects/mir/src/platforms/wayland/display.cpp(290): Throw in function void mir::graphics::wayland::Display::run()
Dynamic exception type: boost::wrapexcept<std::system_error>
std::exception::what: Failed to read Wayland events: Broken pipe


!!! Fatal signal received. Attempting cleanup, but deadlock may occur
Mir fatal error: Unsupported attempt to continue after a fatal signal: SIGABRT
Aborted (core dumped)

Which is less tidy than it should be, but not a deadlock

[Saviq]

The ^C was after the Alt+F4, and the deadlock.