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stasis: Don't hold app_registry and session locks unnecessarily

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resource_events:stasis_app_message_handler() was locking the session,
then attempting to determine if the app had debug enabled which
locked the app_registry container.  res_stasis:__stasis_app_register
was locking the app_registry container then calling app_update
which caused app_handler (which locks the session) to run.
The result was a deadlock.

* Updated resource_events:stasis_app_message_handler() to determine
  if debug was set (which locks the app_registry) before obtaining the
  session lock.

* Updated res_stasis:__stasis_app_register to release the app_registry
  container lock before calling app_update (which locks the sesison).

ASTERISK-28423
Reported by Ross Beer

Change-Id: I58c69d08cb372852a63933608e4d6c3e456247b4
This commit is contained in:
George Joseph
2019-11-06 04:47:17 -07:00
parent ad6314c90f
commit 990a91b44a
2 changed files with 38 additions and 25 deletions
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53
res/res_stasis.c
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@@ -1704,7 +1704,7 @@ struct ao2_container *stasis_app_get_all(void)
static int __stasis_app_register(const char *app_name, stasis_app_cb handler, void *data, int all_events)
{
struct stasis_app *app;
RAII_VAR(struct stasis_app *, app, NULL, ao2_cleanup);
if (!apps_registry) {
return -1;
@@ -1713,36 +1713,43 @@ static int __stasis_app_register(const char *app_name, stasis_app_cb handler, vo
ao2_lock(apps_registry);
app = ao2_find(apps_registry, app_name, OBJ_SEARCH_KEY | OBJ_NOLOCK);
if (app) {
/*
* We need to unlock the apps_registry before calling app_update to
* prevent the possibility of a deadlock with the session. We'll still
* run the lazy cleanup first though.
*/
cleanup();
ao2_unlock(apps_registry);
app_update(app, handler, data);
} else {
app = app_create(app_name, handler, data, all_events ? STASIS_APP_SUBSCRIBE_ALL : STASIS_APP_SUBSCRIBE_MANUAL);
if (!app) {
ao2_unlock(apps_registry);
return -1;
}
if (all_events) {
struct stasis_app_event_source *source;
AST_RWLIST_RDLOCK(&event_sources);
AST_LIST_TRAVERSE(&event_sources, source, next) {
if (!source->subscribe) {
continue;
}
source->subscribe(app, NULL);
}
AST_RWLIST_UNLOCK(&event_sources);
}
ao2_link_flags(apps_registry, app, OBJ_NOLOCK);
return 0;
}
app = app_create(app_name, handler, data, all_events ? STASIS_APP_SUBSCRIBE_ALL : STASIS_APP_SUBSCRIBE_MANUAL);
if (!app) {
ao2_unlock(apps_registry);
return -1;
}
if (all_events) {
struct stasis_app_event_source *source;
AST_RWLIST_RDLOCK(&event_sources);
AST_LIST_TRAVERSE(&event_sources, source, next) {
if (!source->subscribe) {
continue;
}
source->subscribe(app, NULL);
}
AST_RWLIST_UNLOCK(&event_sources);
}
ao2_link_flags(apps_registry, app, OBJ_NOLOCK);
/* We lazily clean up the apps_registry, because it's good enough to
* prevent memory leaks, and we're lazy.
*/
cleanup();
ao2_unlock(apps_registry);
ao2_ref(app, -1);
return 0;
}