From 1d8280c18f96f0cd96d1e7acd62f7250c4da1a84 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Fri, 27 Jan 2017 16:40:12 +0100
Subject: [PATCH] memory: make memory_listener_unregister idempotent
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Make it easy to unregister a MemoryListener without tracking whether it
had been registered before.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 memory.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/memory.c b/memory.c
index 6c58373422..ed8b5aa83e 100644
--- a/memory.c
+++ b/memory.c
@@ -2371,8 +2371,13 @@ void memory_listener_register(MemoryListener *listener, AddressSpace *as)
 
 void memory_listener_unregister(MemoryListener *listener)
 {
+    if (!listener->address_space) {
+        return;
+    }
+
     QTAILQ_REMOVE(&memory_listeners, listener, link);
     QTAILQ_REMOVE(&listener->address_space->listeners, listener, link_as);
+    listener->address_space = NULL;
 }
 
 void address_space_init(AddressSpace *as, MemoryRegion *root, const char *name)
-- 
2.39.2