The prepare function before unlocking BQL.  There're only three places that can
release the BQL: unlock(), cond_wait() or cond_timedwait().

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 cpus.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/cpus.c b/cpus.c
index 5cbc3f30de..48aa295fea 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1832,20 +1832,27 @@ void qemu_mutex_lock_iothread_impl(const char *file, int line)
     iothread_locked = true;
 }
 
+static void qemu_mutex_unlock_iothread_prepare(void)
+{
+}
+
 void qemu_mutex_unlock_iothread(void)
 {
     g_assert(qemu_mutex_iothread_locked());
     iothread_locked = false;
+    qemu_mutex_unlock_iothread_prepare();
     qemu_mutex_unlock(&qemu_global_mutex);
 }
 
 void qemu_cond_wait_iothread(QemuCond *cond)
 {
+    qemu_mutex_unlock_iothread_prepare();
     qemu_cond_wait(cond, &qemu_global_mutex);
 }
 
 void qemu_cond_timedwait_iothread(QemuCond *cond, int ms)
 {
+    qemu_mutex_unlock_iothread_prepare();
     qemu_cond_timedwait(cond, &qemu_global_mutex, ms);
 }
 
-- 
2.24.1