core: Cleanup some channel snapshot staging anomalies.

We shouldn't unlock the channel after starting a snapshot staging because
another thread may interfere and do its own snapshot staging.

* app_dial.c:dial_exec_full() made hold the channel lock while setting up
the outgoing channel staging.  Made hold the channel lock after the called
party answers while updating the caller channel staging.

* chan_sip.c:sip_new() completed the channel staging on off-nominal exit.
Also we need to use ast_hangup() instead of ast_channel_unref() at that
location.

* channel.c:__ast_channel_alloc_ap() added a comment about not needing to
complete the channel snapshot staging on off-nominal exit paths.

* rtp_engine.c:ast_rtp_instance_set_stats_vars() made hold the channel
locks while staging the channels for the stats channel variables.

Change-Id: Iefb6336893163f6447bad65568722ad5d5d8212a

apps/app_dial.c

@@ -2541,16 +2541,14 @@ static int dial_exec_full(struct ast_channel *chan, const char *data, struct ast
 			continue;
 		}
 
-		ast_channel_lock(tc);
-		ast_channel_stage_snapshot(tc);
-		ast_channel_unlock(tc);
-
 		ast_channel_get_device_name(tc, device_name, sizeof(device_name));
 		if (!ignore_cc) {
 			ast_cc_extension_monitor_add_dialstring(chan, tmp->interface, device_name);
 		}
 
 		ast_channel_lock_both(tc, chan);
+		ast_channel_stage_snapshot(tc);
+
 		pbx_builtin_setvar_helper(tc, "DIALEDPEERNUMBER", tmp->number);
 
 		/* Setup outgoing SDP to match incoming one */
@@ -2566,7 +2564,6 @@ static int dial_exec_full(struct ast_channel *chan, const char *data, struct ast
 
 		ast_channel_appl_set(tc, "AppDial");
 		ast_channel_data_set(tc, "(Outgoing Line)");
-		ast_channel_publish_snapshot(tc);
 
 		memset(ast_channel_whentohangup(tc), 0, sizeof(*ast_channel_whentohangup(tc)));
 
@@ -2791,15 +2788,14 @@ static int dial_exec_full(struct ast_channel *chan, const char *data, struct ast
 		}
 	} else {
 		const char *number;
+		const char *name;
 		int dial_end_raised = 0;
 		int cause = -1;
 
-		if (ast_test_flag64(&opts, OPT_CALLER_ANSWER))
+		if (ast_test_flag64(&opts, OPT_CALLER_ANSWER)) {
 			ast_answer(chan);
+		}
 
-		strcpy(pa.status, "ANSWER");
-		ast_channel_stage_snapshot(chan);
-		pbx_builtin_setvar_helper(chan, "DIALSTATUS", pa.status);
 		/* Ah ha!  Someone answered within the desired timeframe.  Of course after this
 		   we will always return with -1 so that it is hung up properly after the
 		   conversation.  */
@@ -2821,10 +2817,10 @@ static int dial_exec_full(struct ast_channel *chan, const char *data, struct ast
 		hanguptree(&out_chans, peer, cause >= 0 ? cause : AST_CAUSE_ANSWERED_ELSEWHERE);
 
 		/* If appropriate, log that we have a destination channel and set the answer time */
-		if (ast_channel_name(peer))
-			pbx_builtin_setvar_helper(chan, "DIALEDPEERNAME", ast_channel_name(peer));
 
 		ast_channel_lock(peer);
+		name = ast_strdupa(ast_channel_name(peer));
+
 		number = pbx_builtin_getvar_helper(peer, "DIALEDPEERNUMBER");
 		if (ast_strlen_zero(number)) {
 			number = NULL;
@@ -2832,8 +2828,16 @@ static int dial_exec_full(struct ast_channel *chan, const char *data, struct ast
 			number = ast_strdupa(number);
 		}
 		ast_channel_unlock(peer);
+
 		ast_channel_lock(chan);
+		ast_channel_stage_snapshot(chan);
+
+		strcpy(pa.status, "ANSWER");
+		pbx_builtin_setvar_helper(chan, "DIALSTATUS", pa.status);
+
+		pbx_builtin_setvar_helper(chan, "DIALEDPEERNAME", name);
 		pbx_builtin_setvar_helper(chan, "DIALEDPEERNUMBER", number);
+
 		ast_channel_stage_snapshot_done(chan);
 		ast_channel_unlock(chan);
 

channels/chan_sip.c

@@ -8141,7 +8141,9 @@ static struct ast_channel *sip_new(struct sip_pvt *i, int state, const char *tit
 		if (!fmt) {
 			ast_log(LOG_WARNING, "No compatible formats could be found for %s\n", ast_channel_name(tmp));
 			ao2_ref(caps, -1);
-			tmp = ast_channel_unref(tmp);
+			ast_channel_stage_snapshot_done(tmp);
+			ast_channel_unlock(tmp);
+			ast_hangup(tmp);
 			return NULL;
 		}
 	}

main/channel.c

@@ -823,7 +823,12 @@ __ast_channel_alloc_ap(int needqueue, int state, const char *cid_num, const char
 	ast_channel_stage_snapshot(tmp);
 
 	if (!(nativeformats = ast_format_cap_alloc(AST_FORMAT_CAP_FLAG_DEFAULT))) {
-		/* format capabilities structure allocation failure */
+		/*
+		 * Aborting the channel creation.  We do not need to complete staging
+		 * the channel snapshot because the channel has not been finalized or
+		 * linked into the channels container yet.  Nobody else knows about
+		 * this channel nor will anybody ever know about it.
+		 */
 		return ast_channel_unref(tmp);
 	}
 	ast_format_cap_append(nativeformats, ast_format_none, 0);
@@ -849,6 +854,7 @@ __ast_channel_alloc_ap(int needqueue, int state, const char *cid_num, const char
 
 	if (!(schedctx = ast_sched_context_create())) {
 		ast_log(LOG_WARNING, "Channel allocation failed: Unable to create schedule context\n");
+		/* See earlier channel creation abort comment above. */
 		return ast_channel_unref(tmp);
 	}
 	ast_channel_sched_set(tmp, schedctx);
@@ -863,6 +869,7 @@ __ast_channel_alloc_ap(int needqueue, int state, const char *cid_num, const char
 		ast_channel_caller(tmp)->id.name.valid = 1;
 		ast_channel_caller(tmp)->id.name.str = ast_strdup(cid_name);
 		if (!ast_channel_caller(tmp)->id.name.str) {
+			/* See earlier channel creation abort comment above. */
 			return ast_channel_unref(tmp);
 		}
 	}
@@ -870,6 +877,7 @@ __ast_channel_alloc_ap(int needqueue, int state, const char *cid_num, const char
 		ast_channel_caller(tmp)->id.number.valid = 1;
 		ast_channel_caller(tmp)->id.number.str = ast_strdup(cid_num);
 		if (!ast_channel_caller(tmp)->id.number.str) {
+			/* See earlier channel creation abort comment above. */
 			return ast_channel_unref(tmp);
 		}
 	}
@@ -883,6 +891,7 @@ __ast_channel_alloc_ap(int needqueue, int state, const char *cid_num, const char
 	}
 
 	if (needqueue && ast_channel_internal_alertpipe_init(tmp)) {
+		/* See earlier channel creation abort comment above. */
 		return ast_channel_unref(tmp);
 	}
 
@@ -974,20 +983,14 @@ __ast_channel_alloc_ap(int needqueue, int state, const char *cid_num, const char
 	if (assignedids && (does_id_conflict(assignedids->uniqueid) || does_id_conflict(assignedids->uniqueid2))) {
 		ast_channel_internal_errno_set(AST_CHANNEL_ERROR_ID_EXISTS);
 		ao2_unlock(channels);
-		/* This is a bit unorthodox, but we can't just call ast_channel_stage_snapshot_done()
-		 * because that will result in attempting to publish the channel snapshot. That causes
-		 * badness in some places, such as CDRs. So we need to manually clear the flag on the
-		 * channel that says that a snapshot is being cleared.
-		 */
-		ast_clear_flag(ast_channel_flags(tmp), AST_FLAG_SNAPSHOT_STAGE);
 		ast_channel_unlock(tmp);
+		/* See earlier channel creation abort comment above. */
 		return ast_channel_unref(tmp);
 	}
 
+	/* Finalize and link into the channels container. */
 	ast_channel_internal_finalize(tmp);
-
 	ast_atomic_fetchadd_int(&chancount, +1);
-
 	ao2_link_flags(channels, tmp, OBJ_NOLOCK);
 
 	ao2_unlock(channels);

main/rtp_engine.c

@@ -1899,16 +1899,16 @@ void ast_rtp_instance_set_stats_vars(struct ast_channel *chan, struct ast_rtp_in
 {
 	char quality_buf[AST_MAX_USER_FIELD];
 	char *quality;
-	struct ast_channel *bridge = ast_channel_bridge_peer(chan);
+	struct ast_channel *bridge;
 
-	ast_channel_lock(chan);
+	bridge = ast_channel_bridge_peer(chan);
-	ast_channel_stage_snapshot(chan);
-	ast_channel_unlock(chan);
 	if (bridge) {
-		ast_channel_lock(bridge);
+		ast_channel_lock_both(chan, bridge);
 		ast_channel_stage_snapshot(bridge);
-		ast_channel_unlock(bridge);
+	} else {
+		ast_channel_lock(chan);
 	}
+	ast_channel_stage_snapshot(chan);
 
 	quality = ast_rtp_instance_get_quality(instance, AST_RTP_INSTANCE_STAT_FIELD_QUALITY,
 		quality_buf, sizeof(quality_buf));
@@ -1946,11 +1946,9 @@ void ast_rtp_instance_set_stats_vars(struct ast_channel *chan, struct ast_rtp_in
 		}
 	}
 
-	ast_channel_lock(chan);
 	ast_channel_stage_snapshot_done(chan);
 	ast_channel_unlock(chan);
 	if (bridge) {
-		ast_channel_lock(bridge);
 		ast_channel_stage_snapshot_done(bridge);
 		ast_channel_unlock(bridge);
 		ast_channel_unref(bridge);