[asterisk-commits] jrose: branch 1.8 r353999 - /branches/1.8/channels/chan_agent.c
SVN commits to the Asterisk project
asterisk-commits at lists.digium.com
Fri Feb 3 15:24:49 CST 2012
Author: jrose
Date: Fri Feb 3 15:24:45 2012
New Revision: 353999
URL: http://svnview.digium.com/svn/asterisk?view=rev&rev=353999
Log:
Fixes deadlocks occuring in chan_agent due to r335976
Bad locking order was added to chan_agent to prevent segfaults from having no locking
in a patch by irroot. This patch addresses the bad locking order by releasing locks before
getting the right locking order to stop deadlocks from occuring when doing multiple
interactions with agents.
(closes issue ASTERISK-19285)
Reported by: Alex Villacis Lasso
Review: https://reviewboard.asterisk.org/r/1708/
Modified:
branches/1.8/channels/chan_agent.c
Modified: branches/1.8/channels/chan_agent.c
URL: http://svnview.digium.com/svn/asterisk/branches/1.8/channels/chan_agent.c?view=diff&rev=353999&r1=353998&r2=353999
==============================================================================
--- branches/1.8/channels/chan_agent.c (original)
+++ branches/1.8/channels/chan_agent.c Fri Feb 3 15:24:45 2012
@@ -1,7 +1,7 @@
/*
* Asterisk -- An open source telephony toolkit.
*
- * Copyright (C) 1999 - 2006, Digium, Inc.
+ * Copyright (C) 1999 - 2012, Digium, Inc.
*
* Mark Spencer <markster at digium.com>
*
@@ -375,6 +375,43 @@
};
/*!
+ * \brief Locks the owning channel for a LOCKED pvt while obeying locking order. The pvt
+ * must enter this function locked and will be returned locked, but this function will
+ * unlock the pvt for a short time, so it can't be used while expecting the pvt to remain
+ * static. If function returns a non NULL channel, it will need to be unlocked and
+ * unrefed once it is no longer needed.
+ *
+ * \param pvt Pointer to the LOCKED agent_pvt for which the owner is needed
+ * \ret locked channel which owns the pvt at the time of completion. NULL if not available.
+ */
+static struct ast_channel *agent_lock_owner(struct agent_pvt *pvt)
+{
+ struct ast_channel *owner;
+
+ for (;;) {
+ if (!pvt->owner) { /* No owner. Nothing to do. */
+ return NULL;
+ }
+
+ /* If we don't ref the owner, it could be killed when we unlock the pvt. */
+ owner = ast_channel_ref(pvt->owner);
+
+ /* Locking order requires us to lock channel, then pvt. */
+ ast_mutex_unlock(&pvt->lock);
+ ast_channel_lock(owner);
+ ast_mutex_lock(&pvt->lock);
+
+ /* Check if owner changed during pvt unlock period */
+ if (owner != pvt->owner) { /* Channel changed. Unref and do another pass. */
+ ast_channel_unlock(owner);
+ owner = ast_channel_unref(owner);
+ } else { /* Channel stayed the same. Return it. */
+ return owner;
+ }
+ }
+}
+
+/*!
* Adds an agent to the global list of agents.
*
* \param agent A string with the username, password and real name of an agent. As defined in agents.conf. Example: "13,169,John Smith"
@@ -554,7 +591,11 @@
struct ast_frame *f = NULL;
static struct ast_frame answer_frame = { AST_FRAME_CONTROL, { AST_CONTROL_ANSWER } };
int cur_time = time(NULL);
+ struct ast_channel *owner;
+
ast_mutex_lock(&p->lock);
+ owner = agent_lock_owner(p);
+
CHECK_FORMATS(ast, p);
if (!p->start) {
p->start = cur_time;
@@ -584,13 +625,11 @@
int howlong = cur_time - p->start;
if (p->autologoff && (howlong >= p->autologoff)) {
ast_log(LOG_NOTICE, "Agent '%s' didn't answer/confirm within %d seconds (waited %d)\n", p->name, p->autologoff, howlong);
- if (p->owner || p->chan) {
- while (p->owner && ast_channel_trylock(p->owner)) {
- DEADLOCK_AVOIDANCE(&p->lock);
- }
- if (p->owner) {
- ast_softhangup(p->owner, AST_SOFTHANGUP_EXPLICIT);
- ast_channel_unlock(p->owner);
+ if (owner || p->chan) {
+ if (owner) {
+ ast_softhangup(owner, AST_SOFTHANGUP_EXPLICIT);
+ ast_channel_unlock(owner);
+ owner = ast_channel_unref(owner);
}
while (p->chan && ast_channel_trylock(p->chan)) {
@@ -652,6 +691,11 @@
}
}
+ if (owner) {
+ ast_channel_unlock(owner);
+ owner = ast_channel_unref(owner);
+ }
+
CLEANUP(ast,p);
if (p->chan && !p->chan->_bridge) {
if (strcasecmp(p->chan->tech->type, "Local")) {
@@ -887,6 +931,14 @@
static int agent_hangup(struct ast_channel *ast)
{
struct agent_pvt *p = ast->tech_pvt;
+ struct ast_channel *indicate_chan = NULL;
+ char *tmp_moh; /* moh buffer for indicating after unlocking p */
+
+ if (p->pending) {
+ AST_LIST_LOCK(&agents);
+ AST_LIST_REMOVE(&agents, p, list);
+ AST_LIST_UNLOCK(&agents);
+ }
ast_mutex_lock(&p->lock);
p->owner = NULL;
@@ -909,7 +961,7 @@
if (p->start && (ast->_state != AST_STATE_UP)) {
p->start = 0;
} else
- p->start = 0;
+ p->start = 0;
if (p->chan) {
p->chan->_bridge = NULL;
/* If they're dead, go ahead and hang up on the agent now */
@@ -918,14 +970,20 @@
ast_softhangup(p->chan, AST_SOFTHANGUP_EXPLICIT);
ast_channel_unlock(p->chan);
} else if (p->loginstart) {
- ast_channel_lock(p->chan);
- ast_indicate_data(p->chan, AST_CONTROL_HOLD,
- S_OR(p->moh, NULL),
- !ast_strlen_zero(p->moh) ? strlen(p->moh) + 1 : 0);
- ast_channel_unlock(p->chan);
+ indicate_chan = ast_channel_ref(p->chan);
+ tmp_moh = ast_strdupa(p->moh);
}
}
ast_mutex_unlock(&p->lock);
+
+ if (indicate_chan) {
+ ast_channel_lock(indicate_chan);
+ ast_indicate_data(indicate_chan, AST_CONTROL_HOLD,
+ S_OR(tmp_moh, NULL),
+ !ast_strlen_zero(tmp_moh) ? strlen(tmp_moh) + 1 : 0);
+ ast_channel_unlock(indicate_chan);
+ indicate_chan = ast_channel_unref(indicate_chan);
+ }
/* Only register a device state change if the agent is still logged in */
if (!p->loginstart) {
@@ -934,11 +992,6 @@
ast_devstate_changed(AST_DEVICE_NOT_INUSE, "Agent/%s", p->agent);
}
- if (p->pending) {
- AST_LIST_LOCK(&agents);
- AST_LIST_REMOVE(&agents, p, list);
- AST_LIST_UNLOCK(&agents);
- }
if (p->abouttograb) {
/* Let the "about to grab" thread know this isn't valid anymore, and let it
kill it later */
@@ -1491,6 +1544,8 @@
/*!
* Lists agents and their status to the Manager API.
* It is registered on load_module() and it gets called by the manager backend.
+ * This function locks both the pvt and the channel that owns it for a while, but
+ * does not keep these locks.
* \param s
* \param m
* \returns
@@ -1513,7 +1568,9 @@
astman_send_ack(s, m, "Agents will follow");
AST_LIST_LOCK(&agents);
AST_LIST_TRAVERSE(&agents, p, list) {
- ast_mutex_lock(&p->lock);
+ struct ast_channel *owner;
+ ast_mutex_lock(&p->lock);
+ owner = agent_lock_owner(p);
/* Status Values:
AGENT_LOGGEDOFF - Agent isn't logged in
@@ -1528,16 +1585,14 @@
if (p->chan) {
loginChan = ast_strdupa(p->chan->name);
- if (p->owner && p->owner->_bridge) {
+ if (owner && owner->_bridge) {
talkingto = S_COR(p->chan->caller.id.number.valid,
p->chan->caller.id.number.str, "n/a");
- ast_channel_lock(p->owner);
- if ((bridge = ast_bridged_channel(p->owner))) {
+ if ((bridge = ast_bridged_channel(owner))) {
talkingtoChan = ast_strdupa(bridge->name);
} else {
talkingtoChan = "n/a";
}
- ast_channel_unlock(p->owner);
status = "AGENT_ONCALL";
} else {
talkingto = "n/a";
@@ -1549,6 +1604,11 @@
talkingto = "n/a";
talkingtoChan = "n/a";
status = "AGENT_LOGGEDOFF";
+ }
+
+ if (owner) {
+ ast_channel_unlock(owner);
+ owner = ast_channel_unref(owner);
}
astman_append(s, "Event: Agents\r\n"
@@ -1582,14 +1642,14 @@
ret = 0;
if (p->owner || p->chan) {
if (!soft) {
+ struct ast_channel *owner;
ast_mutex_lock(&p->lock);
-
- while (p->owner && ast_channel_trylock(p->owner)) {
- DEADLOCK_AVOIDANCE(&p->lock);
- }
- if (p->owner) {
- ast_softhangup(p->owner, AST_SOFTHANGUP_EXPLICIT);
- ast_channel_unlock(p->owner);
+ owner = agent_lock_owner(p);
+
+ if (owner) {
+ ast_softhangup(owner, AST_SOFTHANGUP_EXPLICIT);
+ ast_channel_unlock(owner);
+ owner = ast_channel_unref(owner);
}
while (p->chan && ast_channel_trylock(p->chan)) {
@@ -1726,7 +1786,9 @@
AST_LIST_LOCK(&agents);
AST_LIST_TRAVERSE(&agents, p, list) {
+ struct ast_channel *owner;
ast_mutex_lock(&p->lock);
+ owner = agent_lock_owner(p);
if (p->pending) {
if (p->group)
ast_cli(a->fd, "-- Pending call to group %d\n", powerof(p->group));
@@ -1739,10 +1801,11 @@
username[0] = '\0';
if (p->chan) {
snprintf(location, sizeof(location), "logged in on %s", p->chan->name);
- if (p->owner && ast_bridged_channel(p->owner))
+ if (owner && ast_bridged_channel(owner)) {
snprintf(talkingto, sizeof(talkingto), " talking to %s", ast_bridged_channel(p->owner)->name);
- else
+ } else {
strcpy(talkingto, " is idle");
+ }
online_agents++;
} else {
strcpy(location, "not logged in");
@@ -1755,6 +1818,11 @@
username, location, talkingto, music);
count_agents++;
}
+
+ if (owner) {
+ ast_channel_unlock(owner);
+ owner = ast_channel_unref(owner);
+ }
ast_mutex_unlock(&p->lock);
}
AST_LIST_UNLOCK(&agents);
@@ -1795,21 +1863,32 @@
AST_LIST_LOCK(&agents);
AST_LIST_TRAVERSE(&agents, p, list) {
+ struct ast_channel *owner;
+
agent_status = 0; /* reset it to offline */
ast_mutex_lock(&p->lock);
+ owner = agent_lock_owner(p);
+
if (!ast_strlen_zero(p->name))
snprintf(username, sizeof(username), "(%s) ", p->name);
else
username[0] = '\0';
if (p->chan) {
snprintf(location, sizeof(location), "logged in on %s", p->chan->name);
- if (p->owner && ast_bridged_channel(p->owner))
- snprintf(talkingto, sizeof(talkingto), " talking to %s", ast_bridged_channel(p->owner)->name);
- else
+ if (owner && ast_bridged_channel(owner)) {
+ snprintf(talkingto, sizeof(talkingto), " talking to %s", ast_bridged_channel(owner)->name);
+ } else {
strcpy(talkingto, " is idle");
+ }
agent_status = 1;
online_agents++;
}
+
+ if (owner) {
+ ast_channel_unlock(owner);
+ owner = ast_channel_unref(owner);
+ }
+
if (!ast_strlen_zero(p->moh))
snprintf(music, sizeof(music), " (musiconhold is '%s')", p->moh);
if (agent_status)
@@ -2381,12 +2460,16 @@
AST_LIST_LOCK(&agents);
AST_LIST_TRAVERSE(&agents, p, list) {
+ struct ast_channel *owner;
+
data_agent = ast_data_add_node(data_root, "agent");
if (!data_agent) {
continue;
}
ast_mutex_lock(&p->lock);
+ owner = agent_lock_owner(p);
+
if (!(p->pending)) {
ast_data_add_str(data_agent, "id", p->agent);
ast_data_add_structure(agent_pvt, data_agent, p);
@@ -2397,17 +2480,25 @@
if (!data_channel) {
ast_mutex_unlock(&p->lock);
ast_data_remove_node(data_root, data_agent);
+ if (owner) {
+ ast_channel_unlock(owner);
+ owner = ast_channel_unref(owner);
+ }
continue;
}
ast_channel_data_add_structure(data_channel, p->chan, 0);
- if (p->owner && ast_bridged_channel(p->owner)) {
+ if (owner && ast_bridged_channel(owner)) {
data_talkingto = ast_data_add_node(data_agent, "talkingto");
if (!data_talkingto) {
ast_mutex_unlock(&p->lock);
ast_data_remove_node(data_root, data_agent);
+ if (owner) {
+ ast_channel_unlock(owner);
+ owner = ast_channel_unref(owner);
+ }
continue;
}
- ast_channel_data_add_structure(data_talkingto, ast_bridged_channel(p->owner), 0);
+ ast_channel_data_add_structure(data_talkingto, ast_bridged_channel(owner), 0);
}
} else {
ast_data_add_node(data_agent, "talkingto");
@@ -2415,6 +2506,12 @@
}
ast_data_add_str(data_agent, "musiconhold", p->moh);
}
+
+ if (owner) {
+ ast_channel_unlock(owner);
+ owner = ast_channel_unref(owner);
+ }
+
ast_mutex_unlock(&p->lock);
/* if this agent doesn't match remove the added agent. */
More information about the asterisk-commits
mailing list