Frame deferral: Revert API refactoring.

There are several issues with deferring frames that are caused by the
refactoring.

1) The code deferring frames mishandles adding a deferred frame to the
deferred queue.  As a result the deferred queue can only be one frame
long.

2) Deferrable frames can come directly from the channel driver as well as
the read queue.  These frames need to be added to the deferred queue.

3) Whoever is deferring frames is really only doing the __ast_read() to
collect deferred frames and doesn't care about the returned frames except
to detect a hangup event.  When frame deferral is completed we must make
the normal frame processing see the hangup as a frame anyway.  As such,
there is no need to have varying hangup frame deferral methods.  We also
need to be aware of the AST_SOFTHANGUP_ASYNCGOTO hangup that isn't real.
That fake hangup is to cause the PBX thread to break out of loops to go
execute a new dialplan location.

4) To properly deal with deferrable frames from the channel driver as
pointed out by (2) above, means that it is possible to process a dialplan
interception routine while frames are deferred because of the
AST_CONTROL_READ_ACTION control frame.  Deferring frames is not
implemented as a re-entrant operation so you could have the unsupported
case of two sections of code thinking they have control of the media
stream.

A worse problem is because of the bad implementation of the AMI PlayDTMF
action.  It can cause two threads to be deferring frames on the same
channel at the same time.  (ASTERISK_25940)

* Rather than fix all these problems simply revert the API refactoring as
there is going to be only autoservice and safe_sleep deferring frames
anyway.

ASTERISK-26343

ASTERISK-26716 #close

Change-Id: I45069c779aa3a35b6c863f65245a6df2c7865496

1 files changed, 0 insertions, 49 deletions

diff --git a/include/asterisk/channel.h b/include/asterisk/channel.h
index 1b7246b98..9cf313fc4 100644
--- a/include/asterisk/channel.h
+++ b/include/asterisk/channel.h
@@ -967,16 +967,6 @@ enum {
 	 * The channel is executing a subroutine or macro
 	 */
 	AST_FLAG_SUBROUTINE_EXEC = (1 << 27),
-	/*!
-	 * The channel is currently in an operation where
-	 * frames should be deferred.
-	 */
-	AST_FLAG_DEFER_FRAMES = (1 << 28),
-	/*!
-	 * The channel is currently deferring hangup frames
-	 * in addition to other frame types.
-	 */
-	AST_FLAG_DEFER_HANGUP_FRAMES = (1 << 29),
 };
 
 /*! \brief ast_bridge_config flags */
@@ -4727,43 +4717,4 @@ enum ast_channel_error {
  */
 enum ast_channel_error ast_channel_errno(void);
 
-/*!
- * \brief Retrieve the deferred read queue.
- */
-struct ast_readq_list *ast_channel_deferred_readq(struct ast_channel *chan);
-
-/*!
- * \brief Start deferring deferrable frames on this channel
- *
- * Sometimes, a channel gets entered into a mode where a "main" application
- * is tasked with servicing frames on the channel, but that application does
- * not need to act on those frames. However, it would be imprudent to simply
- * drop important frames. This function can be called so that important frames
- * will be deferred, rather than placed in the channel frame queue as normal.
- *
- * Hangups are an interesting frame type. Hangups will always be detectable by
- * a reader when a channel is deferring frames. If the defer_hangups parameter
- * is non-zero, then the hangup frame will also be duplicated and deferred, so
- * that the next reader of the channel will get the hangup frame, too.
- *
- * \pre chan MUST be locked before calling
- *
- * \param chan The channel on which frames should be deferred
- * \param defer_hangups Defer hangups in addition to other deferrable frames
- */
-void ast_channel_start_defer_frames(struct ast_channel *chan, int defer_hangups);
-
-/*!
- * \brief Stop deferring deferrable frames on this channel
- *
- * When it is time to stop deferring frames on the channel, all deferred frames
- * will be queued onto the channel's read queue so that the next servicer of
- * the channel can handle those frames as necessary.
- *
- * \pre chan MUST be locked before calling
- *
- * \param chan The channel on which to stop deferring frames.
- */
-void ast_channel_stop_defer_frames(struct ast_channel *chan);
-
 #endif /* _ASTERISK_CHANNEL_H */