From 0ad95bc8a048e165148c68c5bdec5555b25218a9 Mon Sep 17 00:00:00 2001 From: Frederic LE FOLL Date: Thu, 8 Jun 2017 19:28:12 +0200 Subject: Core/PBX: Deadlock between dialplan execution and application unregistration. Not easy to reproduce, but we have noticed deadlocks when unloading a module while dialplan is handling a request. The deadlock is between : 1) Dialplan execution: pbx_extension_helper() first taking conlock, then pbx_findapp() [when called] asking for lock on apps list. 2) Application unregistration: ast_unregister_application() first taking lock on apps list, then unreference_cached_app() [when called] asking for conlock. As a protection, I suggest to modify ast_unregister_application(), so that it anticipates the need of conlock, before taking the lock on apps list. The side effect is a longer unavailability of conlock when unregistering an application. ASTERISK-27041 Change-Id: I0db0f1eb320da6a5758cce3a47d765be1face8e2 --- main/pbx_app.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'main') diff --git a/main/pbx_app.c b/main/pbx_app.c index e0609db70..ec6bc7589 100644 --- a/main/pbx_app.c +++ b/main/pbx_app.c @@ -394,6 +394,11 @@ int ast_unregister_application(const char *app) struct ast_app *cur; int cmp; + /* Anticipate need for conlock in unreference_cached_app(), in order to avoid + * possible deadlock with pbx_extension_helper()/pbx_findapp() + */ + ast_rdlock_contexts(); + AST_RWLIST_WRLOCK(&apps); AST_RWLIST_TRAVERSE_SAFE_BEGIN(&apps, cur, list) { cmp = strcasecmp(app, cur->name); @@ -416,6 +421,8 @@ int ast_unregister_application(const char *app) AST_RWLIST_TRAVERSE_SAFE_END; AST_RWLIST_UNLOCK(&apps); + ast_unlock_contexts(); + return cur ? 0 : -1; } -- cgit v1.2.3