memory: unregister AddressSpace MemoryListener within BQL

address_space_destroy_dispatch is called from an RCU callback and hence
outside the iothread mutex (BQL).  However, after address_space_destroy
no new accesses can hit the destroyed AddressSpace so it is not necessary
to observe changes to the memory map.  Move the memory_listener_unregister
call earlier, to make it thread-safe again.

Reported-by: Alex Williamson <alex.williamson@redhat.com>
Fixes: 374f2981d1f10bc4307f250f24b2a7ddb9b14be0
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/exec.c b/exec.c
index 6b79ad1d11..6dff7bc43a 100644
--- a/exec.c
+++ b/exec.c
@@ -2059,11 +2059,15 @@ void address_space_init_dispatch(AddressSpace *as)
     memory_listener_register(&as->dispatch_listener, as);
 }
 
+void address_space_unregister(AddressSpace *as)
+{
+    memory_listener_unregister(&as->dispatch_listener);
+}
+
 void address_space_destroy_dispatch(AddressSpace *as)
 {
     AddressSpaceDispatch *d = as->dispatch;
 
-    memory_listener_unregister(&as->dispatch_listener);
     g_free(d);
     as->dispatch = NULL;
 }