Inside exec.c, there is a race:
-------
static bool prepare_mmio_access(MemoryRegion *mr)
{
bool unlocked = !qemu_mutex_iothread_locked();
bool release_lock = false;
if (unlocked && mr->global_locking) {
qemu_mutex_lock_iothread();
------
IMHO, checking for unlocked that way is wrong. Should use some kind
of _trylock instead?
