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

1 files changed, 11 insertions, 11 deletions

diff --git a/res/res_pjsip_header_funcs.c b/res/res_pjsip_header_funcs.c
index 6c0f9151d..798a1cde6 100644
--- a/res/res_pjsip_header_funcs.c
+++ b/res/res_pjsip_header_funcs.c
@@ -153,7 +153,7 @@ static const struct ast_datastore_info header_datastore = {
 	.type = "header_datastore",
 };
 
-/*! \brief Data structure used for ast_sip_push_task_synchronous  */
+/*! \brief Data structure used for ast_sip_push_task_wait_serializer  */
 struct header_data {
 	struct ast_sip_channel_pvt *channel;
 	char *header_name;
@@ -480,11 +480,11 @@ static int func_read_header(struct ast_channel *chan, const char *function, char
 	header_data.len = len;
 
 	if (!strcasecmp(args.action, "read")) {
-		return ast_sip_push_task_synchronous(channel->session->serializer, read_header,
-											 &header_data);
+		return ast_sip_push_task_wait_serializer(channel->session->serializer,
+			read_header, &header_data);
 	} else if (!strcasecmp(args.action, "remove")) {
-		return ast_sip_push_task_synchronous(channel->session->serializer, remove_header,
-											 &header_data);
+		return ast_sip_push_task_wait_serializer(channel->session->serializer,
+			remove_header, &header_data);
 	} else {
 		ast_log(AST_LOG_ERROR,
 				"Unknown action '%s' is not valid, must be 'read' or 'remove'.\n",
@@ -539,14 +539,14 @@ static int func_write_header(struct ast_channel *chan, const char *cmd, char *da
 	header_data.len = 0;
 
 	if (!strcasecmp(args.action, "add")) {
-		return ast_sip_push_task_synchronous(channel->session->serializer, add_header,
-											 &header_data);
+		return ast_sip_push_task_wait_serializer(channel->session->serializer,
+			add_header, &header_data);
 	} else if (!strcasecmp(args.action, "update")) {
-		return ast_sip_push_task_synchronous(channel->session->serializer, update_header,
-											 &header_data);
+		return ast_sip_push_task_wait_serializer(channel->session->serializer,
+			update_header, &header_data);
 	} else if (!strcasecmp(args.action, "remove")) {
-		return ast_sip_push_task_synchronous(channel->session->serializer, remove_header,
-											 &header_data);
+		return ast_sip_push_task_wait_serializer(channel->session->serializer,
+			remove_header, &header_data);
 	} else {
 		ast_log(AST_LOG_ERROR,
 				"Unknown action '%s' is not valid, must be 'add', 'update', or 'remove'.\n",