channel locking: Add locking for channel snapshot creation

Original commit message by mmichelson (asterisk 12 r403311):

"This adds channel locks around calls to create channel snapshots as well
as other functions which operate on a channel and then end up
creating a channel snapshot. Functions that expect the channel to be
locked prior to being called have had their documentation updated to
indicate such."

The above was initially committed and then reverted at r403398.  The problem
was found to be in core_local.c in the publish_local_bridge_message function.
The ast_unreal_lock_all function locks and adds a reference to the returned
channels and while they were being unlocked they were not being unreffed when
no longer needed.  Fixed by unreffing the channels.

Also in bridge.c a lock was obtained on "other->chan", but then an attempt was
made to unlock "other" and not the previously locked channel.  Fixed by
unlocking "other->chan"

(closes issue ASTERISK-22709)
Reported by: John Bigelow
........

Merged revisions 404237 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@404260 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 21 insertions, 0 deletions

diff --git a/include/asterisk/stasis_bridges.h b/include/asterisk/stasis_bridges.h
index 2d15a3332..72bf59948 100644
--- a/include/asterisk/stasis_bridges.h
+++ b/include/asterisk/stasis_bridges.h
@@ -203,6 +203,9 @@ struct stasis_message_type *ast_channel_left_bridge_type(void);
  * should also be treated as immutable and not modified after it is put into the
  * message.
  *
+ * \pre bridge is locked.
+ * \pre No channels are locked.
+ *
  * \param bridge Channel blob is associated with, or NULL for global/all bridges.
  * \param blob JSON object representing the data.
  * \return \ref ast_bridge_blob message.
@@ -217,6 +220,9 @@ struct stasis_message *ast_bridge_blob_create(struct stasis_message_type *type,
  * \since 12
  * \brief Publish a bridge channel enter event
  *
+ * \pre bridge is locked.
+ * \pre No channels are locked.
+ *
  * \param bridge The bridge a channel entered
  * \param chan The channel that entered the bridge
  * \param swap The channel being swapped out of the bridge
@@ -228,6 +234,9 @@ void ast_bridge_publish_enter(struct ast_bridge *bridge, struct ast_channel *cha
  * \since 12
  * \brief Publish a bridge channel leave event
  *
+ * \pre bridge is locked.
+ * \pre No channels are locked.
+ *
  * \param bridge The bridge a channel left
  * \param chan The channel that left the bridge
  */
@@ -272,6 +281,8 @@ struct stasis_message_type *ast_blind_transfer_type(void);
 /*!
  * \brief Publish a blind transfer event
  *
+ * \pre No channels or bridges are locked
+ *
  * \param is_external Whether the blind transfer was initiated externally (e.g. via AMI or native protocol)
  * \param result The success or failure of the transfer
  * \param to_transferee The bridge between the transferer and transferee plus the transferer channel
@@ -335,6 +346,8 @@ struct stasis_message_type *ast_attended_transfer_type(void);
  * Publish an \ref ast_attended_transfer_message with the dest_type set to
  * \c AST_ATTENDED_TRANSFER_DEST_FAIL.
  *
+ * \pre No channels or bridges are locked
+ *
  * \param is_external Indicates if the transfer was initiated externally
  * \param result The result of the transfer. Will always be a type of failure.
  * \param transferee The bridge between the transferer and transferees as well as the transferer channel from that bridge
@@ -356,6 +369,8 @@ void ast_bridge_publish_attended_transfer_fail(int is_external, enum ast_transfe
  *
  * In either case, two bridges enter, one leaves.
  *
+ * \pre No channels or bridges are locked
+ *
  * \param is_external Indicates if the transfer was initiated externally
  * \param result The result of the transfer.
  * \param transferee The bridge between the transferer and transferees as well as the transferer channel from that bridge
@@ -375,6 +390,8 @@ void ast_bridge_publish_attended_transfer_bridge_merge(int is_external, enum ast
  * this results from merging two bridges together. The difference is that a
  * transferer channel survives the bridge merge
  *
+ * \pre No channels or bridges are locked
+ *
  * \param is_external Indicates if the transfer was initiated externally
  * \param result The result of the transfer.
  * \param transferee The bridge between the transferer and transferees as well as the transferer channel from that bridge
@@ -396,6 +413,8 @@ void ast_bridge_publish_attended_transfer_threeway(int is_external, enum ast_tra
  * \li A transferee channel leaving a bridge to run an app
  * \li A bridge of transferees running an app (via a local channel)
  *
+ * \pre No channels or bridges are locked
+ *
  * \param is_external Indicates if the transfer was initiated externally
  * \param result The result of the transfer.
  * \param transferee The bridge between the transferer and transferees as well as the transferer channel from that bridge
@@ -419,6 +438,8 @@ void ast_bridge_publish_attended_transfer_app(int is_external, enum ast_transfer
  * When this type of transfer occurs, the two bridges continue to exist after the
  * transfer and a local channel is used to link the two bridges together.
  *
+ * \pre No channels or bridges are locked
+ *
  * \param is_external Indicates if the transfer was initiated externally
  * \param result The result of the transfer.
  * \param transferee The bridge between the transferer and transferees as well as the transferer channel from that bridge