From c11f4d9df6342635987cca10e8c0bae1f329669b Mon Sep 17 00:00:00 2001
From: Mark Spencer <markster@digium.com>
Date: Wed, 9 Jul 2003 22:41:51 +0000
Subject: Fix race in Agents

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@1173 65c4cc65-6c06-0410-ace0-fbb531ad65f3
---
 channels/chan_agent.c | 44 ++++++++++++++++++++++++++++++++++++--------
 1 file changed, 36 insertions(+), 8 deletions(-)

diff --git a/channels/chan_agent.c b/channels/chan_agent.c
index d487428e5..b514043fb 100755
--- a/channels/chan_agent.c
+++ b/channels/chan_agent.c
@@ -79,6 +79,7 @@ static struct agent_pvt {
 	pthread_mutex_t lock;				/* Channel private lock */
 	int dead;							/* Poised for destruction? */
 	int pending;						/* Not a real agent -- just pending a match */
+	int abouttograb;					/* About to grab */
 	unsigned int group;					/* Group memberships */
 	char moh[80];						/* Which music on hold */
 	char agent[AST_MAX_AGENT];			/* Agent ID */
@@ -175,6 +176,21 @@ static struct agent_pvt *add_agent(char *agent, int pending)
 	return p;
 }
 
+static int agent_cleanup(struct agent_pvt *p)
+{
+	struct ast_channel *chan = p->owner;
+	p->owner = NULL;
+	chan->pvt->pvt = NULL;
+	p->app_sleep_cond = 1;
+	/* Release ownership of the agent to other threads (presumably running the login app). */
+	ast_pthread_mutex_unlock(&p->app_lock);
+	if (chan)
+		ast_channel_free(chan);
+	if (p->dead)
+		free(p);
+	return 0;
+}
+
 static int check_availability(struct agent_pvt *newlyavailable, int needlock);
 
 static int agent_answer(struct ast_channel *ast)
@@ -352,9 +368,13 @@ static int agent_hangup(struct ast_channel *ast)
 		agent_unlink(p);
 		ast_pthread_mutex_unlock(&agentlock);
 	}
-	if (p->dead)
+	if (p->abouttograb) {
+		/* Let the "about to grab" thread know this isn't valid anymore, and let it
+		   kill it later */
+		p->abouttograb = 0;
+	} else if (p->dead) {
 		free(p);
-	else {
+	} else {
 		/* Not dead -- check availability now */
 		ast_pthread_mutex_lock(&p->lock);
 		check_availability(p, 1);
@@ -549,6 +569,7 @@ static int check_availability(struct agent_pvt *newlyavailable, int needlock)
 			/* We found a pending call, time to merge */
 			chan = agent_new(newlyavailable, AST_STATE_DOWN);
 			parent = p->owner;
+			p->abouttograb = 1;
 			ast_pthread_mutex_unlock(&p->lock);
 			break;
 		}
@@ -566,13 +587,20 @@ static int check_availability(struct agent_pvt *newlyavailable, int needlock)
 			ast_log( LOG_DEBUG, "Waited for stream, result '%d'\n", res);
 		}
 		if (!res) {
-			ast_setstate(parent, AST_STATE_UP);
-			ast_setstate(chan, AST_STATE_UP);
-			ast_channel_masquerade(parent, chan);
-			ast_hangup(chan);
+			/* Note -- parent may have disappeared */
+			if (p->abouttograb) {
+				ast_setstate(parent, AST_STATE_UP);
+				ast_setstate(chan, AST_STATE_UP);
+				ast_channel_masquerade(parent, chan);
+				p->abouttograb = 0;
+				ast_hangup(chan);
+			} else {
+				ast_log(LOG_DEBUG, "Sneaky, parent disappeared in the mean time...\n");
+				agent_cleanup(newlyavailable);
+			}
 		} else {
-			ast_log(LOG_NOTICE, "Not sure this will always work..\n");
-			ast_hangup(chan);
+			ast_log(LOG_DEBUG, "Ugh...  Agent hung up at exactly the wrong time\n");
+			agent_cleanup(newlyavailable);
 		}
 	}
 	return 0;
-- 
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