res_pjsip.c: Split ast_sip_push_task_synchronous() to fit expectations.

ast_sip_push_task_synchronous() did not necessarily execute the passed in
task under the specified serializer.  If the current thread is any
registered pjsip thread then it would execute the task immediately instead
of under the specified serializer.  Reentrancy issues could result if the
task does not execute with the right serializer.

The original reason ast_sip_push_task_synchronous() checked to see if the
current thread was a registered pjsip thread was because of a deadlock
with masquerades and the channel technology's fixup callback
(ASTERISK_22936).  A subsequent masquerade deadlock fix (ASTERISK_24356)
involving call pickups avoided the original deadlock situation entirely.
The PJSIP channel technology's fixup callback no longer needed to call
ast_sip_push_task_synchronous().

However, there are a few places where this unexpected behavior is still
required to avoid deadlocks.  The pjsip monitor thread executes callbacks
that do calls to ast_sip_push_task_synchronous() that would deadlock if
the task were actually pushed to the specified serializer.  I ran into one
dealing with the pubsub subscriptions where an ao2 destructor called
ast_sip_push_task_synchronous().

* Split ast_sip_push_task_synchronous() into
ast_sip_push_task_wait_servant() and ast_sip_push_task_wait_serializer().
ast_sip_push_task_wait_servant() has the old behavior of
ast_sip_push_task_synchronous().  ast_sip_push_task_wait_serializer() has
the new behavior where the task is always executed by the specified
serializer or a picked serializer if one is not passed in.  Both functions
behave the same if the current thread is not a SIP servant.

* Redirected ast_sip_push_task_synchronous() to
ast_sip_push_task_wait_servant() to preserve API for released branches.

ASTERISK_26806

Change-Id: Id040fa42c0e5972f4c8deef380921461d213b9f3

2 files changed, 7 insertions, 7 deletions

diff --git a/channels/chan_pjsip.c b/channels/chan_pjsip.c
index 6b2664819..dde7416c3 100644
--- a/channels/chan_pjsip.c
+++ b/channels/chan_pjsip.c
@@ -718,7 +718,7 @@ static int chan_pjsip_answer(struct ast_channel *ast)
 	   can occur between this thread and bridging (specifically when native bridging
 	   attempts to do direct media) */
 	ast_channel_unlock(ast);
-	res = ast_sip_push_task_synchronous(session->serializer, answer, session);
+	res = ast_sip_push_task_wait_serializer(session->serializer, answer, session);
 	if (res) {
 		if (res == -1) {
 			ast_log(LOG_ERROR,"Cannot answer '%s': Unable to push answer task to the threadpool.\n",
@@ -2502,10 +2502,10 @@ static struct ast_channel *chan_pjsip_request_with_stream_topology(const char *t
 
 	req_data.topology = topology;
 	req_data.dest = data;
-	/* Default failure value in case ast_sip_push_task_synchronous() itself fails. */
+	/* Default failure value in case ast_sip_push_task_wait_servant() itself fails. */
 	req_data.cause = AST_CAUSE_FAILURE;
 
-	if (ast_sip_push_task_synchronous(NULL, request, &req_data)) {
+	if (ast_sip_push_task_wait_servant(NULL, request, &req_data)) {
 		*cause = req_data.cause;
 		return NULL;
 	}
diff --git a/channels/pjsip/dialplan_functions.c b/channels/pjsip/dialplan_functions.c
index aa376f892..ce347dcd9 100644
--- a/channels/pjsip/dialplan_functions.c
+++ b/channels/pjsip/dialplan_functions.c
@@ -897,7 +897,7 @@ int pjsip_acf_channel_read(struct ast_channel *chan, const char *cmd, char *data
 	func_args.field = args.field;
 	func_args.buf = buf;
 	func_args.len = len;
-	if (ast_sip_push_task_synchronous(func_args.session->serializer, read_pjsip, &func_args)) {
+	if (ast_sip_push_task_wait_serializer(func_args.session->serializer, read_pjsip, &func_args)) {
 		ast_log(LOG_WARNING, "Unable to read properties of channel %s: failed to push task\n", ast_channel_name(chan));
 		ao2_ref(func_args.session, -1);
 		return -1;
@@ -1219,7 +1219,7 @@ int pjsip_acf_media_offer_write(struct ast_channel *chan, const char *cmd, char
 		mdata.media_type = AST_MEDIA_TYPE_VIDEO;
 	}
 
-	return ast_sip_push_task_synchronous(channel->session->serializer, media_offer_write_av, &mdata);
+	return ast_sip_push_task_wait_serializer(channel->session->serializer, media_offer_write_av, &mdata);
 }
 
 int pjsip_acf_dtmf_mode_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
@@ -1390,7 +1390,7 @@ int pjsip_acf_dtmf_mode_write(struct ast_channel *chan, const char *cmd, char *d
 
 	ast_channel_unlock(chan);
 
-	return ast_sip_push_task_synchronous(channel->session->serializer, dtmf_mode_refresh_cb, &rdata);
+	return ast_sip_push_task_wait_serializer(channel->session->serializer, dtmf_mode_refresh_cb, &rdata);
 }
 
 static int refresh_write_cb(void *obj)
@@ -1438,5 +1438,5 @@ int pjsip_acf_session_refresh_write(struct ast_channel *chan, const char *cmd, c
 		rdata.method = AST_SIP_SESSION_REFRESH_METHOD_UPDATE;
 	}
 
-	return ast_sip_push_task_synchronous(channel->session->serializer, refresh_write_cb, &rdata);
+	return ast_sip_push_task_wait_serializer(channel->session->serializer, refresh_write_cb, &rdata);
 }