Merged revisions 351182 via svnmerge from

https://origsvn.digium.com/svn/asterisk/branches/1.8

........
  r351182 | russell | 2012-01-16 20:37:03 -0500 (Mon, 16 Jan 2012) | 22 lines
  
  Add some missing locking in chan_sip.
  
  This patch adds some missing locking to the function 
  send_provisional_keepalive_full().  This function is called from the scheduler,
  which is processed in the SIP monitor thread.  The associated channel (or pbx)
  thread will also be using the same sip_pvt and ast_channel so locking must be
  used.  The sip_pvt_lock_full() function is used to ensure proper locking order
  in a safe manner.
  
  In passing, document a suspected reference counting error in this function.
  The "fix" is left commented out because when the "fix" is present, crashes
  occur.  My theory is that fixing it is exposing a reference counting error
  elsewhere, but I don't know where.  (Or my analysis of this being a problem
  could have been completely wrong in the first place).  Leave the comment in
  the code for so that someone may investigate it again in the future.
  
  Also add a bit of doxygen to transmit_provisional_response().
  
  (closes issue ASTERISK-18979)
  
  Review: https://reviewboard.asterisk.org/r/1648
........


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/10@351183 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -4096,6 +4096,10 @@ static void add_blank(struct sip_request *req)
 static int send_provisional_keepalive_full(struct sip_pvt *pvt, int with_sdp)
 {
 	const char *msg = NULL;
+	struct ast_channel *chan;
+	int res = 0;
+
+	chan = sip_pvt_lock_full(pvt);
 
 	if (!pvt->last_provisional || !strncasecmp(pvt->last_provisional, "100", 3)) {
 		msg = "183 Session Progress";
@@ -4107,10 +4111,35 @@ static int send_provisional_keepalive_full(struct sip_pvt *pvt, int with_sdp)
 		} else {
 			transmit_response(pvt, S_OR(msg, pvt->last_provisional), &pvt->initreq);
 		}
-		return PROVIS_KEEPALIVE_TIMEOUT;
+		res = PROVIS_KEEPALIVE_TIMEOUT;
 	}
 
-	return 0;
+	if (chan) {
+		ast_channel_unlock(chan);
+		chan = ast_channel_unref(chan);
+	}
+
+	if (!res) {
+		pvt->provisional_keepalive_sched_id = -1;
+	}
+
+	sip_pvt_unlock(pvt);
+
+#if 0
+	/*
+	 * XXX BUG TODO
+	 *
+	 * Without this code, it appears as if this function is leaking its
+	 * reference to the sip_pvt.  However, adding it introduces a crash.
+	 * This points to some sort of reference count imbalance elsewhere,
+	 * but I'm not sure where ...
+	 */
+	if (!res) {
+		dialog_unref(pvt, "dialog ref for provisional keepalive");
+	}
+#endif
+
+	return res;
 }
 
 static int send_provisional_keepalive(const void *data) {
@@ -10898,7 +10927,13 @@ static void get_realm(struct sip_pvt *p, const struct sip_request *req)
 	ast_string_field_set(p, realm, sip_cfg.realm);
 }
 
-/* Only use a static string for the msg, here! */
+/*!
+ * \internal
+ *
+ * \arg msg Only use a string constant for the msg, here, it is shallow copied
+ *
+ * \note assumes the sip_pvt is locked.
+ */
 static int transmit_provisional_response(struct sip_pvt *p, const char *msg, const struct sip_request *req, int with_sdp)
 {
 	int res;