lib: Add a GPU error detector

If we listen to the uevents from the kernel, we can detect when the GPU
hangs. This requires us to fork a helper process to do so and send a
signal back to the parent.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

tests/gem_exec_whisper.c

@@ -368,6 +368,8 @@ igt_main
 	igt_fixture
 		fd = drm_open_driver_master(DRIVER_INTEL);
 
+	igt_fork_hang_detector(fd);
+
 	for (const struct mode *m = modes; m->name; m++)
 		igt_subtest_f("%s", *m->name ? m->name : "basic")
 			whisper(fd, -1, m->flags);
@@ -382,6 +384,8 @@ igt_main
 				whisper(fd, e->exec_id | e->flags, m->flags);
 	}
 
+	igt_stop_hang_detector();
+
 	igt_fixture
 		close(fd);
 }