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: http://svn.digium.com/svn/asterisk/trunk@190423 f38db490-d61c-443f-a65b-d21fe96a405b

4 files changed, 134 insertions, 55 deletions

diff --git a/res/res_agi.c b/res/res_agi.c
index efd8549b3..24dd5d0bb 100644
--- a/res/res_agi.c
+++ b/res/res_agi.c
@@ -543,20 +543,27 @@ static char *handle_cli_agi_add_cmd(struct ast_cli_entry *e, int cmd, struct ast
 		return NULL;
 	}
 
-	if (a->argc < 4)
+	if (a->argc < 4) {
 		return CLI_SHOWUSAGE;
-	chan = ast_get_channel_by_name_locked(a->argv[2]);
-	if (!chan) {
+	}
+
+	if (!(chan = ast_channel_get_by_name(a->argv[2]))) {
 		ast_log(LOG_WARNING, "Channel %s does not exists or cannot lock it\n", a->argv[2]);
 		return CLI_FAILURE;
 	}
+
 	if (add_agi_cmd(chan, a->argv[3], (a->argc > 4 ? a->argv[4] : ""))) {
 		ast_log(LOG_WARNING, "failed to add AGI command to queue of channel %s\n", chan->name);
 		ast_channel_unlock(chan);
+		chan = ast_channel_unref(chan);
 		return CLI_FAILURE;
 	}
+
 	ast_log(LOG_DEBUG, "Added AGI command to channel %s queue\n", chan->name);
+
 	ast_channel_unlock(chan);
+	chan = ast_channel_unref(chan);
+
 	return CLI_SUCCESS;
 }
 
@@ -578,24 +585,33 @@ static int action_add_agi_cmd(struct mansession *s, const struct message *m)
 	const char *cmdid   = astman_get_header(m, "CommandID");
 	struct ast_channel *chan;
 	char buf[256];
+
 	if (ast_strlen_zero(channel) || ast_strlen_zero(cmdbuff)) {
 		astman_send_error(s, m, "Both, Channel and Command are *required*");
 		return 0;
 	}
-	chan = ast_get_channel_by_name_locked(channel);
-	if (!chan) {
+
+	if (!(chan = ast_channel_get_by_name(channel))) {
 		snprintf(buf, sizeof(buf), "Channel %s does not exists or cannot get its lock", channel);
 		astman_send_error(s, m, buf);
 		return 0;
 	}
+
+	ast_channel_lock(chan);
+
 	if (add_agi_cmd(chan, cmdbuff, cmdid)) {
 		snprintf(buf, sizeof(buf), "Failed to add AGI command to channel %s queue", chan->name);
 		astman_send_error(s, m, buf);
 		ast_channel_unlock(chan);
+		chan = ast_channel_unref(chan);
 		return 0;
 	}
-	astman_send_ack(s, m, "Added AGI command to queue");
+
 	ast_channel_unlock(chan);
+	chan = ast_channel_unref(chan);
+
+	astman_send_ack(s, m, "Added AGI command to queue");
+
 	return 0;
 }
 
@@ -1679,12 +1695,11 @@ static int handle_hangup(struct ast_channel *chan, AGI *agi, int argc, char **ar
 		return RESULT_SUCCESS;
 	} else if (argc == 2) {
 		/* one argument: look for info on the specified channel */
-		c = ast_get_channel_by_name_locked(argv[1]);
-		if (c) {
+		if ((c = ast_channel_get_by_name(argv[1]))) {
 			/* we have a matching channel */
-			ast_softhangup(c,AST_SOFTHANGUP_EXPLICIT);
+			ast_softhangup(c, AST_SOFTHANGUP_EXPLICIT);
+			c = ast_channel_unref(c);
 			ast_agi_send(agi->fd, chan, "200 result=1\n");
-			ast_channel_unlock(c);
 			return RESULT_SUCCESS;
 		}
 		/* if we get this far no channel name matched the argument given */
@@ -1766,10 +1781,9 @@ static int handle_channelstatus(struct ast_channel *chan, AGI *agi, int argc, ch
 		return RESULT_SUCCESS;
 	} else if (argc == 3) {
 		/* one argument: look for info on the specified channel */
-		c = ast_get_channel_by_name_locked(argv[2]);
-		if (c) {
+		if ((c = ast_channel_get_by_name(argv[2]))) {
 			ast_agi_send(agi->fd, chan, "200 result=%d\n", c->_state);
-			ast_channel_unlock(c);
+			c = ast_channel_unref(c);
 			return RESULT_SUCCESS;
 		}
 		/* if we get this far no channel name matched the argument given */
@@ -1817,21 +1831,27 @@ static int handle_getvariablefull(struct ast_channel *chan, AGI *agi, int argc,
 	char tmp[4096];
 	struct ast_channel *chan2=NULL;
 
-	if ((argc != 4) && (argc != 5))
+	if (argc != 4 && argc != 5) {
 		return RESULT_SHOWUSAGE;
+	}
+
 	if (argc == 5) {
-		chan2 = ast_get_channel_by_name_locked(argv[4]);
+		chan2 = ast_channel_get_by_name(argv[4]);
 	} else {
-		chan2 = chan;
+		chan2 = ast_channel_ref(chan);
 	}
+
 	if (chan2) {
 		pbx_substitute_variables_helper(chan2, argv[3], tmp, sizeof(tmp) - 1);
 		ast_agi_send(agi->fd, chan, "200 result=1 (%s)\n", tmp);
 	} else {
 		ast_agi_send(agi->fd, chan, "200 result=0\n");
 	}
-	if (chan2 && (chan2 != chan))
-		ast_channel_unlock(chan2);
+
+	if (chan2) {
+		chan2 = ast_channel_unref(chan2);
+	}
+
 	return RESULT_SUCCESS;
 }
 
diff --git a/res/res_clioriginate.c b/res/res_clioriginate.c
index 4ed08a44e..beb2522f4 100644
--- a/res/res_clioriginate.c
+++ b/res/res_clioriginate.c
@@ -201,15 +201,14 @@ static char *handle_redirect(struct ast_cli_entry *e, int cmd, struct ast_cli_ar
 	name = a->argv[2];
 	dest = a->argv[3];
 
-	chan = ast_get_channel_by_name_locked(name);
-	if (!chan) {
+	if (!(chan = ast_channel_get_by_name(name))) {
 		ast_cli(a->fd, "Channel '%s' not found\n", name);
 		return CLI_FAILURE;
 	}
 
 	res = ast_async_parseable_goto(chan, dest);
 
-	ast_channel_unlock(chan);
+	chan = ast_channel_unref(chan);
 
 	if (!res) {
 		ast_cli(a->fd, "Channel '%s' successfully redirected to %s\n", name, dest);
diff --git a/res/res_monitor.c b/res/res_monitor.c
index 6bd96fbca..dde35a9be 100644
--- a/res/res_monitor.c
+++ b/res/res_monitor.c
@@ -579,34 +579,41 @@ static int start_monitor_action(struct mansession *s, const struct message *m)
 		astman_send_error(s, m, "No channel specified");
 		return 0;
 	}
-	c = ast_get_channel_by_name_locked(name);
-	if (!c) {
+
+	if (!(c = ast_channel_get_by_name(name))) {
 		astman_send_error(s, m, "No such channel");
 		return 0;
 	}
 
 	if (ast_strlen_zero(fname)) {
-		/* No filename base specified, default to channel name as per CLI */		
+		/* No filename base specified, default to channel name as per CLI */
+		ast_channel_lock(c);
 		fname = ast_strdupa(c->name);
+		ast_channel_unlock(c);
 		/* Channels have the format technology/channel_name - have to replace that /  */
-		if ((d = strchr(fname, '/'))) 
+		if ((d = strchr(fname, '/'))) {
 			*d = '-';
+		}
 	}
 
 	if (ast_monitor_start(c, format, fname, 1, X_REC_IN | X_REC_OUT)) {
 		if (ast_monitor_change_fname(c, fname, 1)) {
 			astman_send_error(s, m, "Could not start monitoring channel");
-			ast_channel_unlock(c);
+			c = ast_channel_unref(c);
 			return 0;
 		}
 	}
 
 	if (ast_true(mix)) {
+		ast_channel_lock(c);
 		ast_monitor_setjoinfiles(c, 1);
+		ast_channel_unlock(c);
 	}
 
-	ast_channel_unlock(c);
+	c = ast_channel_unref(c);
+
 	astman_send_ack(s, m, "Started monitoring channel");
+
 	return 0;
 }
 
@@ -621,22 +628,28 @@ static int stop_monitor_action(struct mansession *s, const struct message *m)
 	struct ast_channel *c = NULL;
 	const char *name = astman_get_header(m, "Channel");
 	int res;
+
 	if (ast_strlen_zero(name)) {
 		astman_send_error(s, m, "No channel specified");
 		return 0;
 	}
-	c = ast_get_channel_by_name_locked(name);
-	if (!c) {
+
+	if (!(c = ast_channel_get_by_name(name))) {
 		astman_send_error(s, m, "No such channel");
 		return 0;
 	}
+
 	res = ast_monitor_stop(c, 1);
-	ast_channel_unlock(c);
+
+	c = ast_channel_unref(c);
+
 	if (res) {
 		astman_send_error(s, m, "Could not stop monitoring channel");
 		return 0;
 	}
+
 	astman_send_ack(s, m, "Stopped monitoring channel");
+
 	return 0;
 }
 
@@ -654,26 +667,32 @@ static int change_monitor_action(struct mansession *s, const struct message *m)
 	struct ast_channel *c = NULL;
 	const char *name = astman_get_header(m, "Channel");
 	const char *fname = astman_get_header(m, "File");
+
 	if (ast_strlen_zero(name)) {
 		astman_send_error(s, m, "No channel specified");
 		return 0;
 	}
+
 	if (ast_strlen_zero(fname)) {
 		astman_send_error(s, m, "No filename specified");
 		return 0;
 	}
-	c = ast_get_channel_by_name_locked(name);
-	if (!c) {
+
+	if (!(c = ast_channel_get_by_name(name))) {
 		astman_send_error(s, m, "No such channel");
 		return 0;
 	}
+
 	if (ast_monitor_change_fname(c, fname, 1)) {
+		c = ast_channel_unref(c);
 		astman_send_error(s, m, "Could not change monitored filename of channel");
-		ast_channel_unlock(c);
 		return 0;
 	}
-	ast_channel_unlock(c);
+
+	c = ast_channel_unref(c);
+
 	astman_send_ack(s, m, "Changed monitor filename");
+
 	return 0;
 }
 
@@ -688,31 +707,33 @@ enum MONITOR_PAUSING_ACTION
 	MONITOR_ACTION_PAUSE,
 	MONITOR_ACTION_UNPAUSE
 };
-	  
+ 
 static int do_pause_or_unpause(struct mansession *s, const struct message *m, int action)
 {
 	struct ast_channel *c = NULL;
 	const char *name = astman_get_header(m, "Channel");
-	
+
 	if (ast_strlen_zero(name)) {
 		astman_send_error(s, m, "No channel specified");
 		return -1;
 	}
-	
-	c = ast_get_channel_by_name_locked(name);
-	if (!c) {
+
+	if (!(c = ast_channel_get_by_name(name))) {
 		astman_send_error(s, m, "No such channel");
 		return -1;
 	}
 
-	if (action == MONITOR_ACTION_PAUSE)
+	if (action == MONITOR_ACTION_PAUSE) {
 		ast_monitor_pause(c);
-	else
+	} else {
 		ast_monitor_unpause(c);
-	
-	ast_channel_unlock(c);
+	}
+
+	c = ast_channel_unref(c);
+
 	astman_send_ack(s, m, (action == MONITOR_ACTION_PAUSE ? "Paused monitoring of the channel" : "Unpaused monitoring of the channel"));
-	return 0;	
+
+	return 0;
 }
 
 static char pause_monitor_action_help[] =
diff --git a/res/snmp/agent.c b/res/snmp/agent.c
index f7e08220d..5a13142d2 100644
--- a/res/snmp/agent.c
+++ b/res/snmp/agent.c
@@ -236,19 +236,32 @@ static u_char *ast_var_channels_table(struct variable *vp, oid *name, size_t *le
 	u_char *ret = NULL;
 	int i, bit;
 	struct ast_str *out = ast_str_alloca(2048);
+	struct ast_channel_iterator *iter;
 
 	if (header_simple_table(vp, name, length, exact, var_len, write_method, ast_active_channels()))
 		return NULL;
 
 	i = name[*length - 1] - 1;
-	for (chan = ast_channel_walk_locked(NULL);
-		 chan && i;
-		 chan = ast_channel_walk_locked(chan), i--)
-		ast_channel_unlock(chan);
-	if (chan == NULL)
+
+	if (!(iter = ast_channel_iterator_all_new(0))) {
 		return NULL;
+	}
+
+	while ((chan = ast_channel_iterator_next(iter)) && i) {
+		ast_channel_unref(chan);
+		i--;
+	}
+
+	iter = ast_channel_iterator_destroy(iter);
+
+	if (chan == NULL) {
+		return NULL;
+	}
+
 	*var_len = sizeof(long_ret);
 
+	ast_channel_lock(chan);
+
 	switch (vp->magic) {
 	case ASTCHANINDEX:
 		long_ret = name[*length - 1];
@@ -503,7 +516,10 @@ static u_char *ast_var_channels_table(struct variable *vp, oid *name, size_t *le
 	default:
 		break;
 	}
+
 	ast_channel_unlock(chan);
+	chan = ast_channel_unref(chan);
+
 	return ret;
 }
 
@@ -567,13 +583,26 @@ static u_char *ast_var_channel_types_table(struct variable *vp, oid *name, size_
 		long_ret = tech->transfer ? 1 : 2;
 		return (u_char *)&long_ret;
 	case ASTCHANTYPECHANNELS:
+	{
+		struct ast_channel_iterator *iter;
+
 		long_ret = 0;
-		for (chan = ast_channel_walk_locked(NULL); chan; chan = ast_channel_walk_locked(chan)) {
-			if (chan->tech == tech)
+
+		if (!(iter = ast_channel_iterator_all_new(0))) {
+			return NULL;
+		}
+
+		while ((chan = ast_channel_iterator_next(iter))) {
+			if (chan->tech == tech) {
 				long_ret++;
-			ast_channel_unlock(chan);
+			}
+			chan = ast_channel_unref(chan);
 		}
+
+		ast_channel_iterator_destroy(iter);
+
 		return (u_char *)&long_ret;
+	}
 	default:
 		break;
 	}
@@ -585,15 +614,25 @@ static u_char *ast_var_channel_bridge(struct variable *vp, oid *name, size_t *le
 {
 	static unsigned long long_ret;
 	struct ast_channel *chan = NULL;
+	struct ast_channel_iterator *iter;
 
 	long_ret = 0;
-	if (header_generic(vp, name, length, exact, var_len, write_method))
+
+	if (header_generic(vp, name, length, exact, var_len, write_method)) {
 		return NULL;
+	}
 
-	while ((chan = ast_channel_walk_locked(chan))) {
-		if (ast_bridged_channel(chan))
+	if (!(iter = ast_channel_iterator_all_new(0))) {
+		return NULL;
+	}
+
+	while ((chan = ast_channel_iterator_next(iter))) {
+		ast_channel_lock(chan);
+		if (ast_bridged_channel(chan)) {
 			long_ret++;
+		}
 		ast_channel_unlock(chan);
+		chan = ast_channel_unref(chan);
 	}
 
 	*var_len = sizeof(long_ret);