chan_pjsip: Fix deadlock when masquerading PJSIP channels.

Performing a directed call pickup resulted in a deadlock when PJSIP
channels were involved.

A masquerade needs to hold onto the channel locks while it swaps channel
information between the two channels involved in the masquerade.  With
PJSIP channels, the fixup routine needed to push a fixup task onto the
PJSIP channel's serializer.  Unfortunately, if the serializer was also
processing a task that needed to lock the channel, you get deadlock.

* Added a new control frame that is used to notify the channels that a
masquerade is about to start and when it has completed.

* Added the ability to query taskprocessors if the current thread is the
taskprocessor thread.

* Added the ability to suspend/unsuspend the PJSIP serializer thread so a
masquerade could fixup the PJSIP channel without using the serializer.

ASTERISK-24356 #close
Reported by: rmudgett

Review: https://reviewboard.asterisk.org/r/4034/
........

Merged revisions 424471 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/13@424472 65c4cc65-6c06-0410-ace0-fbb531ad65f3

7 files changed, 35 insertions, 25 deletions

diff --git a/channels/chan_iax2.c b/channels/chan_iax2.c
index a3fb34c23..d093438c8 100644
--- a/channels/chan_iax2.c
+++ b/channels/chan_iax2.c
@@ -1421,6 +1421,8 @@ static int iax2_is_control_frame_allowed(int subtype)
 		/* Only meaningful across a bridge on this machine for direct-media exchange. */
 	case AST_CONTROL_PVT_CAUSE_CODE:
 		/* Intended only for the sending machine's local channel structure. */
+	case AST_CONTROL_MASQUERADE_NOTIFY:
+		/* Intended only for masquerades when calling ast_indicate_data(). */
 	case AST_CONTROL_STREAM_STOP:
 	case AST_CONTROL_STREAM_SUSPEND:
 	case AST_CONTROL_STREAM_RESTART:
@@ -5770,6 +5772,7 @@ static int iax2_indicate(struct ast_channel *c, int condition, const void *data,
 		}
 		break;
 	case AST_CONTROL_PVT_CAUSE_CODE:
+	case AST_CONTROL_MASQUERADE_NOTIFY:
 		res = -1;
 		goto done;
 	}
diff --git a/channels/chan_misdn.c b/channels/chan_misdn.c
index f3d540d42..8011b8f28 100644
--- a/channels/chan_misdn.c
+++ b/channels/chan_misdn.c
@@ -7108,6 +7108,7 @@ static int misdn_indication(struct ast_channel *ast, int cond, const void *data,
 		chan_misdn_log(1, p->bc->port, " --> * Unknown Indication:%d pid:%d\n", cond, p->bc->pid);
 		/* fallthrough */
 	case AST_CONTROL_PVT_CAUSE_CODE:
+	case AST_CONTROL_MASQUERADE_NOTIFY:
 		return -1;
 	}
 
diff --git a/channels/chan_motif.c b/channels/chan_motif.c
index 374632ff9..2582a0eeb 100644
--- a/channels/chan_motif.c
+++ b/channels/chan_motif.c
@@ -1805,6 +1805,7 @@ static int jingle_indicate(struct ast_channel *ast, int condition, const void *d
 	case AST_CONTROL_CONNECTED_LINE:
 		break;
 	case AST_CONTROL_PVT_CAUSE_CODE:
+	case AST_CONTROL_MASQUERADE_NOTIFY:
 	case -1:
 		res = -1;
 		break;
diff --git a/channels/chan_pjsip.c b/channels/chan_pjsip.c
index 015cd6448..ea55df799 100644
--- a/channels/chan_pjsip.c
+++ b/channels/chan_pjsip.c
@@ -701,40 +701,24 @@ static int chan_pjsip_write(struct ast_channel *ast, struct ast_frame *frame)
 	return res;
 }
 
-struct fixup_data {
-	struct ast_sip_session *session;
-	struct ast_channel *chan;
-};
-
-static int fixup(void *data)
-{
-	struct fixup_data *fix_data = data;
-	struct ast_sip_channel_pvt *channel = ast_channel_tech_pvt(fix_data->chan);
-	struct chan_pjsip_pvt *pvt = channel->pvt;
-
-	channel->session->channel = fix_data->chan;
-	set_channel_on_rtp_instance(pvt, ast_channel_uniqueid(fix_data->chan));
-
-	return 0;
-}
-
 /*! \brief Function called by core to change the underlying owner channel */
 static int chan_pjsip_fixup(struct ast_channel *oldchan, struct ast_channel *newchan)
 {
 	struct ast_sip_channel_pvt *channel = ast_channel_tech_pvt(newchan);
-	struct fixup_data fix_data;
-
-	fix_data.session = channel->session;
-	fix_data.chan = newchan;
+	struct chan_pjsip_pvt *pvt = channel->pvt;
 
 	if (channel->session->channel != oldchan) {
 		return -1;
 	}
 
-	if (ast_sip_push_task_synchronous(channel->session->serializer, fixup, &fix_data)) {
-		ast_log(LOG_WARNING, "Unable to perform channel fixup\n");
-		return -1;
-	}
+	/*
+	 * The masquerade has suspended the channel's session
+	 * serializer so we can safely change it outside of
+	 * the serializer thread.
+	 */
+	channel->session->channel = newchan;
+
+	set_channel_on_rtp_instance(pvt, ast_channel_uniqueid(newchan));
 
 	return 0;
 }
@@ -1211,6 +1195,24 @@ static int chan_pjsip_indicate(struct ast_channel *ast, int condition, const voi
 	case AST_CONTROL_PVT_CAUSE_CODE:
 		res = -1;
 		break;
+	case AST_CONTROL_MASQUERADE_NOTIFY:
+		ast_assert(datalen == sizeof(int));
+		if (*(int *) data) {
+			/*
+			 * Masquerade is beginning:
+			 * Wait for session serializer to get suspended.
+			 */
+			ast_channel_unlock(ast);
+			ast_sip_session_suspend(channel->session);
+			ast_channel_lock(ast);
+		} else {
+			/*
+			 * Masquerade is complete:
+			 * Unsuspend the session serializer.
+			 */
+			ast_sip_session_unsuspend(channel->session);
+		}
+		break;
 	case AST_CONTROL_HOLD:
 		chan_pjsip_add_hold(ast_channel_uniqueid(ast));
 		device_buf_size = strlen(ast_channel_name(ast)) + 1;
diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index d1ac4ca56..9ea43af99 100644
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -7847,6 +7847,7 @@ static int sip_indicate(struct ast_channel *ast, int condition, const void *data
 		res = -1;
 		break;
 	case AST_CONTROL_PVT_CAUSE_CODE: /* these should be handled by the code in channel.c */
+	case AST_CONTROL_MASQUERADE_NOTIFY:
 	case -1:
 		res = -1;
 		break;
diff --git a/channels/chan_skinny.c b/channels/chan_skinny.c
index a04a63bab..9c074ec6e 100644
--- a/channels/chan_skinny.c
+++ b/channels/chan_skinny.c
@@ -5336,6 +5336,7 @@ static int skinny_indicate(struct ast_channel *ast, int ind, const void *data, s
 		ast_log(LOG_WARNING, "Don't know how to indicate condition %d\n", ind);
 		/* fallthrough */
 	case AST_CONTROL_PVT_CAUSE_CODE:
+	case AST_CONTROL_MASQUERADE_NOTIFY:
 		return -1; /* Tell asterisk to provide inband signalling */
 	}
 	return 0;
diff --git a/channels/chan_unistim.c b/channels/chan_unistim.c
index caa60ad69..7820d051d 100644
--- a/channels/chan_unistim.c
+++ b/channels/chan_unistim.c
@@ -5369,6 +5369,7 @@ static int unistim_indicate(struct ast_channel *ast, int ind, const void *data,
 		ast_log(LOG_WARNING, "Don't know how to indicate condition %d\n", ind);
 		/* fallthrough */
 	case AST_CONTROL_PVT_CAUSE_CODE:
+	case AST_CONTROL_MASQUERADE_NOTIFY:
 		return -1;
 	}