Backport crash fix from trunk to 1.4, whereby 'core show gracefully' could crash...

(closes issue #16470)
 Reported by: kjotte

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@248012 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/main/loader.c b/main/loader.c
index 98284b178797a0e417694348f380db64038a9b68..5d79e53714741a849d5405a96716270cf8e778b0 100644 (file)
--- a/main/loader.c
+++ b/main/loader.c
@@ -449,26 +449,39 @@ static struct ast_module *load_dynamic_module(const char *resource_in, enum modu
 void ast_module_shutdown(void)
 {
        struct ast_module *mod;
-       AST_LIST_HEAD_NOLOCK_STATIC(local_module_list, ast_module);
-
-       /* We have to call the unload() callbacks in reverse order that the modules
-        * exist in the module list so it is the reverse order of how they were
-        * loaded. */
+       int somethingchanged = 1, final = 0;
 
        AST_LIST_LOCK(&module_list);
-       while ((mod = AST_LIST_REMOVE_HEAD(&module_list, entry)))
-               AST_LIST_INSERT_HEAD(&local_module_list, mod, entry);
-       AST_LIST_UNLOCK(&module_list);
 
-       while ((mod = AST_LIST_REMOVE_HEAD(&local_module_list, entry))) {
-               if (mod->info->unload)
-                       mod->info->unload();
-               /* Since this should only be called when shutting down "gracefully",
-                * all channels should be down before we get to this point, meaning
-                * there will be no module users left. */
-               AST_LIST_HEAD_DESTROY(&mod->users);
-               free(mod);
-       }
+       /*!\note Some resources, like timers, are started up dynamically, and thus
+        * may be still in use, even if all channels are dead.  We must therefore
+        * check the usecount before asking modules to unload. */
+       do {
+               if (!somethingchanged) {
+                       /*!\note If we go through the entire list without changing
+                        * anything, ignore the usecounts and unload, then exit. */
+                       final = 1;
+               }
+
+               /* Reset flag before traversing the list */
+               somethingchanged = 0;
+
+               AST_LIST_TRAVERSE_SAFE_BEGIN(&module_list, mod, entry) {
+                       if (!final && mod->usecount) {
+                               continue;
+                       }
+                       AST_LIST_REMOVE_CURRENT(&module_list, entry);
+                       if (mod->info->unload) {
+                               mod->info->unload();
+                       }
+                       AST_LIST_HEAD_DESTROY(&mod->users);
+                       free(mod);
+                       somethingchanged = 1;
+               }
+               AST_LIST_TRAVERSE_SAFE_END;
+       } while (somethingchanged && !final);
+
+       AST_LIST_UNLOCK(&module_list);
 }
 
 int ast_unload_resource(const char *resource_name, enum ast_module_unload_mode force)