From f93033b8ee08ad290af1dfdcabf071ef777eb28d Mon Sep 17 00:00:00 2001
From: alecdavis <alecdavis@f38db490-d61c-443f-a65b-d21fe96a405b>
Date: Fri, 25 Feb 2011 18:58:10 +0000
Subject: [PATCH] Merged revisions 308945 via svnmerge from
 https://origsvn.digium.com/svn/asterisk/branches/1.8

........
  r308945 | alecdavis | 2011-02-26 07:52:53 +1300 (Sat, 26 Feb 2011) | 21 lines

  Fix Deadlock with attended transfer of SIP call

  Call path
    sip_set_rtp_peer (locks chan then pvt)
     transmit_reinvite_with_sdp
      try_suggested_sip_codec
       pbx_builtin_getvar_helper (locks p->owner)

  But by the time p->owner lock was attempted, seems as though chan and p->owner were different.

  So in sip_set_rtp_peer, lock pvt first then lock p->owner using deadlocking methods.

  (closes issue #18837)
  Reported by: alecdavis
  Patches:
        bug18837-trunk.diff3.txt uploaded by alecdavis (license 585)
  Tested by: alecdavis, Irontec, ZX81, cmaj

  Review: [https://reviewboard.asterisk.org/r/1126/]
........


git-svn-id: http://svn.digium.com/svn/asterisk/trunk@308946 f38db490-d61c-443f-a65b-d21fe96a405b
---
 channels/chan_sip.c | 35 +++++++++++++++++++++++++++++++----
 1 file changed, 31 insertions(+), 4 deletions(-)

diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index e9ef2d695..79e570b39 100644
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -27966,7 +27966,20 @@ static int sip_set_udptl_peer(struct ast_channel *chan, struct ast_udptl *udptl)
 	if (!p) {
 		return -1;
 	}
+	/*
+	 * Lock both the pvt and it's owner safely.
+	 */
 	sip_pvt_lock(p);
+	while (p->owner && ast_channel_trylock(p->owner)) {
+		sip_pvt_unlock(p);
+		usleep(1);
+		sip_pvt_lock(p);
+	}
+
+	if (!p->owner) {
+		sip_pvt_unlock(p);
+		return 0;
+	}
 	if (udptl) {
 		ast_udptl_get_peer(udptl, &p->udptlredirip);
 	} else {
@@ -27985,6 +27998,7 @@ static int sip_set_udptl_peer(struct ast_channel *chan, struct ast_udptl *udptl)
 	}
 	/* Reset lastrtprx timer */
 	p->lastrtprx = p->lastrtptx = time(NULL);
+	ast_channel_unlock(p->owner);
 	sip_pvt_unlock(p);
 	return 0;
 }
@@ -28102,12 +28116,25 @@ static int sip_set_rtp_peer(struct ast_channel *chan, struct ast_rtp_instance *i
 		return 0;
 	}
 
-	ast_channel_lock(chan);
+	/*
+	 * Lock both the pvt and it's owner safely.
+	 */
 	sip_pvt_lock(p);
+	while (p->owner && ast_channel_trylock(p->owner)) {
+		sip_pvt_unlock(p);
+		usleep(1);
+		sip_pvt_lock(p);
+	}
+
+	if (!p->owner) {
+		sip_pvt_unlock(p);
+		return 0;
+	}
+
 	if (p->alreadygone) {
 		/* If we're destroyed, don't bother */
+		ast_channel_unlock(p->owner);
 		sip_pvt_unlock(p);
-		ast_channel_unlock(chan);
 		return 0;
 	}
 
@@ -28115,8 +28142,8 @@ static int sip_set_rtp_peer(struct ast_channel *chan, struct ast_rtp_instance *i
 	   that are known to be behind a NAT, then stop the process now
 	*/
 	if (nat_active && !ast_test_flag(&p->flags[0], SIP_DIRECT_MEDIA_NAT)) {
+		ast_channel_unlock(p->owner);
 		sip_pvt_unlock(p);
-		ast_channel_unlock(chan);
 		return 0;
 	}
 
@@ -28158,8 +28185,8 @@ static int sip_set_rtp_peer(struct ast_channel *chan, struct ast_rtp_instance *i
 	}
 	/* Reset lastrtprx timer */
 	p->lastrtprx = p->lastrtptx = time(NULL);
+	ast_channel_unlock(p->owner);
 	sip_pvt_unlock(p);
-	ast_channel_unlock(chan);
 	return 0;
 }