chan_sip.c: Adjust how dialog_unlink_all() stops scheduled events.

This patch is part of a series to resolve deadlocks in chan_sip.c.

* Make dialog_unlink_all() unschedule all items at once in the sched
thread.

ASTERISK-25023

Change-Id: I7743072fb228836e8228b72f6dc46c8cc50b3fb4

diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index 2719372089e30a396bfdab10df18a91eb167cd84..b9facff0c224c636530a57a6d39ec797702a9f4c 100644 (file)
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -3245,6 +3245,60 @@ static void ref_proxy(struct sip_pvt *pvt, struct sip_proxy *proxy)
        }
 }
 
+static void do_dialog_unlink_sched_items(struct sip_pvt *dialog)
+{
+       struct sip_pkt *cp;
+
+       /* remove all current packets in this dialog */
+       sip_pvt_lock(dialog);
+       while ((cp = dialog->packets)) {
+               /* Unlink the node from the list. */
+               dialog->packets = dialog->packets->next;
+
+               /* Destroy the packet object. */
+               AST_SCHED_DEL(sched, cp->retransid);
+               dialog_unref(cp->owner, "Unlink dialog removing all retransmitable packets");
+               ast_free(cp->data);
+               ast_free(cp);
+       }
+       sip_pvt_unlock(dialog);
+
+       AST_SCHED_DEL_UNREF(sched, dialog->waitid,
+               dialog_unref(dialog, "Stop scheduled waitid"));
+
+       AST_SCHED_DEL_UNREF(sched, dialog->initid,
+               dialog_unref(dialog, "Stop scheduled initid"));
+
+       AST_SCHED_DEL_UNREF(sched, dialog->reinviteid,
+               dialog_unref(dialog, "Stop scheduled reinviteid"));
+
+       AST_SCHED_DEL_UNREF(sched, dialog->autokillid,
+               dialog_unref(dialog, "Stop scheduled autokillid"));
+
+       AST_SCHED_DEL_UNREF(sched, dialog->request_queue_sched_id,
+               dialog_unref(dialog, "Stop scheduled request_queue_sched_id"));
+
+       AST_SCHED_DEL_UNREF(sched, dialog->provisional_keepalive_sched_id,
+               dialog_unref(dialog, "Stop scheduled provisional keepalive"));
+
+       AST_SCHED_DEL_UNREF(sched, dialog->t38id,
+               dialog_unref(dialog, "Stop scheduled t38id"));
+
+       if (dialog->stimer) {
+               stop_session_timer(dialog);
+       }
+}
+
+/* Run by the sched thread. */
+static int __dialog_unlink_sched_items(const void *data)
+{
+       struct sip_pvt *dialog = (void *) data;
+
+       do_dialog_unlink_sched_items(dialog);
+       dialog_unref(dialog, "Stop scheduled items for unlink action");
+       return 0;
+}
+
 /*!
  * \brief Unlink a dialog from the dialogs container, as well as any other places
  * that it may be currently stored.
@@ -3254,7 +3308,6 @@ static void ref_proxy(struct sip_pvt *pvt, struct sip_proxy *proxy)
  */
 void dialog_unlink_all(struct sip_pvt *dialog)
 {
-       struct sip_pkt *cp;
        struct ast_channel *owner;
 
        dialog_ref(dialog, "Let's bump the count in the unlink so it doesn't accidentally become dead before we are done");
@@ -3292,41 +3345,14 @@ void dialog_unlink_all(struct sip_pvt *dialog)
                dialog->relatedpeer->call = dialog_unref(dialog->relatedpeer->call, "unset the relatedpeer->call field in tandem with relatedpeer field itself");
        }
 
-       /* remove all current packets in this dialog */
-       while((cp = dialog->packets)) {
-               dialog->packets = dialog->packets->next;
-               AST_SCHED_DEL(sched, cp->retransid);
-               dialog_unref(cp->owner, "remove all current packets in this dialog, and the pointer to the dialog too as part of __sip_destroy");
-               if (cp->data) {
-                       ast_free(cp->data);
-               }
-               ast_free(cp);
-       }
-
-       AST_SCHED_DEL_UNREF(sched, dialog->waitid, dialog_unref(dialog, "when you delete the waitid sched, you should dec the refcount for the stored dialog ptr"));
-
-       AST_SCHED_DEL_UNREF(sched, dialog->initid, dialog_unref(dialog, "when you delete the initid sched, you should dec the refcount for the stored dialog ptr"));
-
-       if (dialog->reinviteid > -1) {
-               AST_SCHED_DEL_UNREF(sched, dialog->reinviteid, dialog_unref(dialog, "clear ref for reinvite_timeout"));
-       }
-
-       if (dialog->autokillid > -1) {
-               AST_SCHED_DEL_UNREF(sched, dialog->autokillid, dialog_unref(dialog, "when you delete the autokillid sched, you should dec the refcount for the stored dialog ptr"));
-       }
-
-       if (dialog->request_queue_sched_id > -1) {
-               AST_SCHED_DEL_UNREF(sched, dialog->request_queue_sched_id, dialog_unref(dialog, "when you delete the request_queue_sched_id sched, you should dec the refcount for the stored dialog ptr"));
-       }
-
-       AST_SCHED_DEL_UNREF(sched, dialog->provisional_keepalive_sched_id, dialog_unref(dialog, "when you delete the provisional_keepalive_sched_id, you should dec the refcount for the stored dialog ptr"));
-
-       if (dialog->t38id > -1) {
-               AST_SCHED_DEL_UNREF(sched, dialog->t38id, dialog_unref(dialog, "when you delete the t38id sched, you should dec the refcount for the stored dialog ptr"));
-       }
-
-       if (dialog->stimer) {
-               stop_session_timer(dialog);
+       dialog_ref(dialog, "Stop scheduled items for unlink action");
+       if (ast_sched_add(sched, 0, __dialog_unlink_sched_items, dialog) < 0) {
+               /*
+                * Uh Oh.  Fall back to unscheduling things immediately
+                * despite the potential deadlock risk.
+                */
+               dialog_unref(dialog, "Failed to schedule stop scheduled items for unlink action");
+               do_dialog_unlink_sched_items(dialog);
        }
 
        dialog_unref(dialog, "Let's unbump the count in the unlink so the poor pvt can disappear if it is time");