Merged revisions 281760 via svnmerge from

https://origsvn.digium.com/svn/asterisk/branches/1.8

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  r281760 | mnicholson | 2010-08-11 12:27:59 -0500 (Wed, 11 Aug 2010) | 4 lines
  
  Avoid a deadlock in add_header_max_forwards().
  
  Related to r276951
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git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@281761 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -9038,8 +9038,16 @@ static int add_header_max_forwards(struct sip_pvt *dialog, struct sip_request *r
 	char clen[10];
 	const char *max = NULL;
 
+	/* deadlock avoidance */
+	while (dialog->owner && ast_channel_trylock(dialog->owner)) {
+		sip_pvt_unlock(dialog);
+		usleep(1);
+		sip_pvt_lock(dialog);
+	}
+
 	if (dialog->owner) {
  		max = pbx_builtin_getvar_helper(dialog->owner, "SIP_MAX_FORWARDS");
+		ast_channel_unlock(dialog->owner);
 	}
 
 	/* The channel variable overrides the peer/channel value */