bridge: Hold off more than one imparting channel at a time.

An earlier patch blocked the ast_bridge_impart() call until the channel
either entered the target bridge or it failed.  Unfortuantely, if the
target bridge is stasis and the imprted channel is not a stasis channel,
stasis bounces the channel out of the bridge to come back into the bridge
as a proper stasis channel.  When the channel is bounced out, that
released the block on ast_bridge_impart() to continue.  If the impart was
a result of a transfer, then it became a race to see if the swap channel
would get hung up before the imparted channel could come back into the
stasis bridge.  If the imparted channel won then everything is fine.  If
the swap channel gets hung up first then the transfer will fail because
the swap channel is leaving the bridge.

* Allow a chain of ast_bridge_impart()'s to happen before any are
unblocked to prevent the race condition described above.  When the channel
finally joins the bridge or completely fails to join the bridge then the
ast_bridge_impart() instances are unblocked.

ASTERISK-25947
Reported by: Richard Mudgett

ASTERISK-24649
Reported by: John Bigelow

ASTERISK-24782
Reported by: John Bigelow

Change-Id: I8fef369171f295f580024ab4971e95c799d0dde1

1 files changed, 5 insertions, 33 deletions

diff --git a/include/asterisk/bridge_channel_internal.h b/include/asterisk/bridge_channel_internal.h
index 7f7d5a88b..fb8e781e8 100644
--- a/include/asterisk/bridge_channel_internal.h
+++ b/include/asterisk/bridge_channel_internal.h
@@ -151,47 +151,20 @@ int bridge_channel_internal_push_full(struct ast_bridge_channel *bridge_channel,
 void bridge_channel_internal_pull(struct ast_bridge_channel *bridge_channel);
 
 /*!
- * \brief Internal bridge channel wait condition and associated result.
- */
-struct bridge_channel_internal_cond {
-	/*! Lock for the data structure */
-	ast_mutex_t lock;
-	/*! Wait condition */
-	ast_cond_t cond;
-	/*! Wait until done */
-	int done;
-	/*! The bridge channel */
-	struct ast_bridge_channel *bridge_channel;
-};
-
-/*!
- * \internal
- * \brief Wait for the expected signal.
- * \since 13.5.0
- *
- * \param cond the wait object
- *
- * \return Nothing
- */
-void bridge_channel_internal_wait(struct bridge_channel_internal_cond *cond);
-
-/*!
- * \internal
- * \brief Signal the condition wait.
- * \since 13.5.0
+ * \brief Signal imparting threads to wake up.
+ * \since 13.9.0
  *
- * \param cond the wait object
+ * \param chan Channel imparted that we need to signal.
  *
  * \return Nothing
  */
-void bridge_channel_internal_signal(struct bridge_channel_internal_cond *cond);
+void bridge_channel_impart_signal(struct ast_channel *chan);
 
 /*!
  * \internal
  * \brief Join the bridge_channel to the bridge (blocking)
  *
  * \param bridge_channel The Channel in the bridge
- * \param cond data used for signaling
  *
  * \note The bridge_channel->swap holds a channel reference for the swap
  * channel going into the bridging system.  The ref ensures that the swap
@@ -206,8 +179,7 @@ void bridge_channel_internal_signal(struct bridge_channel_internal_cond *cond);
  * \retval 0 bridge channel successfully joined the bridge
  * \retval -1 bridge channel failed to join the bridge
  */
-int bridge_channel_internal_join(struct ast_bridge_channel *bridge_channel,
-				 struct bridge_channel_internal_cond *cond);
+int bridge_channel_internal_join(struct ast_bridge_channel *bridge_channel);
 
 /*!
  * \internal