diff options
Diffstat (limited to 'pbx.c')
-rw-r--r-- | pbx.c | 27 |
1 files changed, 21 insertions, 6 deletions
@@ -514,6 +514,12 @@ AST_MUTEX_DEFINE_STATIC(applock); /* Lock for the application list */ struct ast_switch *switches = NULL; AST_MUTEX_DEFINE_STATIC(switchlock); /* Lock for switches */ +/* WARNING: + When holding this lock, do _not_ do anything that will cause conlock + to be taken, unless you _already_ hold it. The ast_merge_contexts_and_delete + function will take the locks in conlock/hintlock order, so any other + paths that require both locks must also take them in that order. +*/ AST_MUTEX_DEFINE_STATIC(hintlock); /* Lock for extension state notifys */ static int stateid = 1; struct ast_hint *hints = NULL; @@ -3696,9 +3702,20 @@ void ast_merge_contexts_and_delete(struct ast_context **extcontexts, const char int length; struct ast_state_cb *thiscb, *prevcb; - /* preserve all watchers for hints associated with this registrar */ AST_LIST_HEAD_INIT(&store); + + /* it is very important that this function hold the hintlock _and_ the conlock + during its operation; not only do we need to ensure that the list of contexts + and extensions does not change, but also that no hint callbacks (watchers) are + added or removed during the merge/delete process + + in addition, the locks _must_ be taken in this order, because there are already + other code paths that use this order + */ + ast_mutex_lock(&conlock); ast_mutex_lock(&hintlock); + + /* preserve all watchers for hints associated with this registrar */ for (hint = hints; hint; hint = hint->next) { if (hint->callbacks && !strcmp(registrar, hint->exten->parent->registrar)) { length = strlen(hint->exten->exten) + strlen(hint->exten->parent->name) + 2 + sizeof(*this); @@ -3717,10 +3734,8 @@ void ast_merge_contexts_and_delete(struct ast_context **extcontexts, const char AST_LIST_INSERT_HEAD(&store, this, list); } } - ast_mutex_unlock(&hintlock); tmp = *extcontexts; - ast_mutex_lock(&conlock); if (registrar) { __ast_context_destroy(NULL,registrar); while (tmp) { @@ -3740,7 +3755,6 @@ void ast_merge_contexts_and_delete(struct ast_context **extcontexts, const char *extcontexts = NULL; } else ast_log(LOG_WARNING, "Requested contexts didn't get merged\n"); - ast_mutex_unlock(&conlock); /* restore the watchers for hints that can be found; notify those that cannot be restored @@ -3748,7 +3762,6 @@ void ast_merge_contexts_and_delete(struct ast_context **extcontexts, const char while ((this = AST_LIST_REMOVE_HEAD(&store, list))) { exten = ast_hint_extension(NULL, this->context, this->exten); /* Find the hint in the list of hints */ - ast_mutex_lock(&hintlock); for (hint = hints; hint; hint = hint->next) { if (hint->exten == exten) break; @@ -3771,10 +3784,12 @@ void ast_merge_contexts_and_delete(struct ast_context **extcontexts, const char hint->callbacks = this->callbacks; hint->laststate = this->laststate; } - ast_mutex_unlock(&hintlock); free(this); } + ast_mutex_unlock(&hintlock); + ast_mutex_unlock(&conlock); + return; } |