qom/object: update class cache atomically
The idiom CPU_GET_CLASS(cpu) is fairly extensively used in various
threads and trips of ThreadSanitizer due to the fact it updates
obj->class->object_cast_cache behind the scenes. As this is just a
fast-path cache there is no need to lock updates.
However to ensure defined C11 behaviour across threads we need to use
the plain atomic_read/set primitives and keep the sanitizer happy.
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <
20160930213106.20186-7-alex.bennee@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>