Convert the ast_channel data structure over to the astobj2 framework.
authorRussell Bryant <russell@russellbryant.com>
Fri, 24 Apr 2009 14:04:26 +0000 (14:04 +0000)
committerRussell Bryant <russell@russellbryant.com>
Fri, 24 Apr 2009 14:04:26 +0000 (14:04 +0000)
commitcba19c8a671c76a3969a7d36bc43444792a13a81
tree1812569845aaf29df5f2a18285e73bc1fcc6268c
parentf314c5f13fd84bc2084e183e39b0d1fbec4b9a5a
Convert the ast_channel data structure over to the astobj2 framework.

There is a lot that could be said about this, but the patch is a big
improvement for performance, stability, code maintainability,
and ease of future code development.

The channel list is no longer an unsorted linked list.  The main container
for channels is an astobj2 hash table.  All of the code related to searching
for channels or iterating active channels has been rewritten.  Let n be
the number of active channels.  Iterating the channel list has gone from
O(n^2) to O(n).  Searching for a channel by name went from O(n) to O(1).
Searching for a channel by extension is still O(n), but uses a new method
for doing so, which is more efficient.

The ast_channel object is now a reference counted object.  The benefits
here are plentiful.  Some benefits directly related to issues in the
previous code include:

1) When threads other than the channel thread owning a channel wanted
   access to a channel, it had to hold the lock on it to ensure that it didn't
   go away.  This is no longer a requirement.  Holding a reference is
   sufficient.

2) There are places that now require less dealing with channel locks.

3) There are places where channel locks are held for much shorter periods
   of time.

4) There are places where dealing with more than one channel at a time becomes
   _MUCH_ easier.  ChanSpy is a great example of this.  Writing code in the
   future that deals with multiple channels will be much easier.

Some additional information regarding channel locking and reference count
handling can be found in channel.h, where a new section has been added that
discusses some of the rules associated with it.

Mark Michelson also assisted with the development of this patch.  He did the
conversion of ChanSpy and introduced a new API, ast_autochan, which makes it
much easier to deal with holding on to a channel pointer for an extended period
of time and having it get automatically updated if the channel gets masqueraded.
Mark was also a huge help in the code review process.

Thanks to David Vossel for his assistance with this branch, as well.  David
did the conversion of the DAHDIScan application by making it become a wrapper
for ChanSpy internally.

The changes come from the svn/asterisk/team/russell/ast_channel_ao2 branch.

Review: http://reviewboard.digium.com/r/203/

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@190423 65c4cc65-6c06-0410-ace0-fbb531ad65f3
42 files changed:
CHANGES
UPGRADE.txt
apps/app_channelredirect.c
apps/app_chanspy.c
apps/app_dahdiscan.c [deleted file]
apps/app_directed_pickup.c
apps/app_minivm.c
apps/app_mixmonitor.c
apps/app_senddtmf.c
apps/app_softhangup.c
apps/app_voicemail.c
build_tools/cflags.xml
channels/chan_agent.c
channels/chan_bridge.c
channels/chan_dahdi.c
channels/chan_gtalk.c
channels/chan_iax2.c
channels/chan_local.c
channels/chan_mgcp.c
channels/chan_misdn.c
channels/chan_sip.c
channels/chan_unistim.c
funcs/func_channel.c
funcs/func_global.c
funcs/func_logic.c
funcs/func_odbc.c
include/asterisk/autochan.h [new file with mode: 0644]
include/asterisk/channel.h
include/asterisk/lock.h
main/Makefile
main/autochan.c [new file with mode: 0644]
main/channel.c
main/cli.c
main/devicestate.c
main/features.c
main/logger.c
main/manager.c
main/pbx.c
res/res_agi.c
res/res_clioriginate.c
res/res_monitor.c
res/snmp/agent.c