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
95 lines
2.4 KiB
C
95 lines
2.4 KiB
C
/*
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* Asterisk -- An open source telephony toolkit.
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*
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* Copyright (C) 2009, Digium, Inc.
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*
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* Mark Michelson <mmichelson@digium.com>
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*
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* See http://www.asterisk.org for more information about
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* the Asterisk project. Please do not directly contact
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* any of the maintainers of this project for assistance;
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* the project provides a web site, mailing lists and IRC
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* channels for your use.
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*
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* This program is free software, distributed under the terms of
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* the GNU General Public License Version 2. See the LICENSE file
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* at the top of the source tree.
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*/
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/*!
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* \file
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* \brief "smart" channels
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*
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* \author Mark Michelson <mmichelson@digium.com>
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*/
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#include "asterisk.h"
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ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
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#include "asterisk/autochan.h"
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#include "asterisk/utils.h"
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#include "asterisk/linkedlists.h"
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#include "asterisk/options.h"
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#include "asterisk/channel.h"
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struct ast_autochan *ast_autochan_setup(struct ast_channel *chan)
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{
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struct ast_autochan *autochan;
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if (!chan) {
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return NULL;
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}
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if (!(autochan = ast_calloc(1, sizeof(*autochan)))) {
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return NULL;
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}
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autochan->chan = ast_channel_ref(chan);
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ast_channel_lock(autochan->chan);
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AST_LIST_INSERT_TAIL(&autochan->chan->autochans, autochan, list);
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ast_channel_unlock(autochan->chan);
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ast_debug(1, "Created autochan %p to hold channel %s (%p)\n", autochan, chan->name, chan);
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return autochan;
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}
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void ast_autochan_destroy(struct ast_autochan *autochan)
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{
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struct ast_autochan *autochan_iter;
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ast_channel_lock(autochan->chan);
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AST_LIST_TRAVERSE_SAFE_BEGIN(&autochan->chan->autochans, autochan_iter, list) {
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if (autochan_iter == autochan) {
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AST_LIST_REMOVE_CURRENT(list);
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ast_debug(1, "Removed autochan %p from the list, about to free it\n", autochan);
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break;
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}
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}
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AST_LIST_TRAVERSE_SAFE_END;
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ast_channel_unlock(autochan->chan);
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autochan->chan = ast_channel_unref(autochan->chan);
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ast_free(autochan);
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}
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void ast_autochan_new_channel(struct ast_channel *old_chan, struct ast_channel *new_chan)
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{
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struct ast_autochan *autochan;
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AST_LIST_APPEND_LIST(&new_chan->autochans, &old_chan->autochans, list);
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AST_LIST_TRAVERSE(&new_chan->autochans, autochan, list) {
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if (autochan->chan == old_chan) {
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autochan->chan = ast_channel_unref(old_chan);
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autochan->chan = ast_channel_ref(new_chan);
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ast_debug(1, "Autochan %p used to hold channel %s (%p) but now holds channel %s (%p)\n",
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autochan, old_chan->name, old_chan, new_chan->name, new_chan);
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}
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}
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}
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