tests/iothread: Always connect iothread GSource to a GMainContext
On older versions of glib (anything prior to glib commit
0f056ebe
from May 2019), the implementation of g_source_ref() and
g_source_unref() is not threadsafe for a GSource which is not
attached to a GMainContext.
QEMU's real iothread.c implementation always attaches its
iothread->ctx's GSource to a GMainContext created for that iothread,
so it is OK, but the simple test framework implementation in
tests/iothread.c was not doing this. This was causing intermittent
assertion failures in the test-aio-multithread subtest
"/aio/multi/mutex/contended" test on the BSD hosts. (It's unclear
why only BSD seems to have been affected -- perhaps a combination of
the specific glib version being used in the VMs and their happening
to run on a host with a lot of CPUs).
Borrow the iothread_init_gcontext() from the real iothread.c
and add the corresponding cleanup code and the calls to
g_main_context_push/pop_thread_default() so we actually use
the GMainContext we create.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Message-id:
20200106144552.7205-1-peter.maydell@linaro.org