qemu/queue.h: add QLIST_SAFE_REMOVE()

QLIST_REMOVE() assumes the element is in a list. It also leaves the element's linked list pointers dangling. Introduce a safe version of QLIST_REMOVE() and convert open-coded instances of this pattern. Signed-off-by: Stefan Hajnoczi <[email protected]> Reviewed-by: Sergio Lopez <[email protected]> Message-id: [email protected] Signed-off-by: Stefan Hajnoczi <[email protected]>
stefanha · Feb 22, 2020 · 195ed8c · 195ed8c
1 parent ca8c6b2
commit 195ed8c
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Showing 3 changed files with 16 additions and 7 deletions.
diff --git a/block.c b/block.c
@@ -2636,10 +2636,7 @@ BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs,
 
 static void bdrv_detach_child(BdrvChild *child)
 {
-    if (child->next.le_prev) {
-        QLIST_REMOVE(child, next);
-        child->next.le_prev = NULL;
-    }
+    QLIST_SAFE_REMOVE(child, next);
 
     bdrv_replace_child(child, NULL);
 

diff --git a/chardev/spice.c b/chardev/spice.c
@@ -216,9 +216,7 @@ static void char_spice_finalize(Object *obj)
 
     vmc_unregister_interface(s);
 
-    if (s->next.le_prev) {
-        QLIST_REMOVE(s, next);
-    }
+    QLIST_SAFE_REMOVE(s, next);
 
     g_free((char *)s->sin.subtype);
     g_free((char *)s->sin.portname);

diff --git a/include/qemu/queue.h b/include/qemu/queue.h
@@ -144,6 +144,20 @@ struct {                                                                \
         *(elm)->field.le_prev = (elm)->field.le_next;                   \
 } while (/*CONSTCOND*/0)
 
+/*
+ * Like QLIST_REMOVE() but safe to call when elm is not in a list
+ */
+#define QLIST_SAFE_REMOVE(elm, field) do {                              \
+        if ((elm)->field.le_prev != NULL) {                             \
+                if ((elm)->field.le_next != NULL)                       \
+                        (elm)->field.le_next->field.le_prev =           \
+                            (elm)->field.le_prev;                       \
+                *(elm)->field.le_prev = (elm)->field.le_next;           \
+                (elm)->field.le_next = NULL;                            \
+                (elm)->field.le_prev = NULL;                            \
+        }                                                               \
+} while (/*CONSTCOND*/0)
+
 #define QLIST_FOREACH(var, head, field)                                 \
         for ((var) = ((head)->lh_first);                                \
                 (var);                                                  \