chan_local: resolve a deadlock.

This patch resolves a fairly complex deadlock that can occur with the
combination of chan_local and a dialplan switch, such as dynamic realtime
extensions, which pulls autoservice into the picture when doing a dialplan
lookup.

(closes issue #18818)
Reported by: nic
Patches:
      issue18818.patch uploaded by jthurman (license 614)
      18818.v1.txt uploaded by russell (license 2)
Tested by: nic, jthurman, kterzi, steve-howes, sysreq, IshMalik

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@315446 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/channels/chan_local.c b/channels/chan_local.c
index 3fac7223e82c18d9f7ff5d359695d629c7349018..c7f81cb6dbac8e895ca3afc37c32f61dd1e1c63e 100644 (file)
--- a/channels/chan_local.c
+++ b/channels/chan_local.c
@@ -737,6 +737,9 @@ static int local_call(struct ast_channel *ast, char *dest, int timeout)
        size_t len, namelen;
        char *reduced_dest = ast_strdupa(dest);
        char *slash;
+       struct ast_channel *chan;
+       const char *exten;
+       const char *context;
 
        if (!p || p->owner != ast) {
                return -1;
@@ -821,21 +824,28 @@ static int local_call(struct ast_channel *ast, char *dest, int timeout)
        }
        ast_set_cc_interfaces_chanvar(p->chan, reduced_dest);
 
-       if (!ast_exists_extension(p->chan, p->chan->context, p->chan->exten, 1,
+       chan = ast_channel_ref(p->chan);
+       ao2_unlock(p);
+       exten = ast_strdupa(chan->exten);
+       context = ast_strdupa(chan->context);
+       ast_channel_unlock(chan);
+
+       if (!ast_exists_extension(chan, context, exten, 1,
                S_COR(p->owner->caller.id.number.valid, p->owner->caller.id.number.str, NULL))) {
-               ast_log(LOG_NOTICE, "No such extension/context %s@%s while calling Local channel\n", p->chan->exten, p->chan->context);
-               ao2_unlock(p);
-               ast_channel_unlock(p->chan);
-               ao2_ref(p, -1);
-               return -1;
+               ast_log(LOG_NOTICE, "No such extension/context %s@%s while calling Local channel\n", exten, context);
+               res = -1;
+               goto return_cleanup;
        }
 
        /* Start switch on sub channel */
-       if (!(res = ast_pbx_start(p->chan)))
+       if (!(res = ast_pbx_start(chan))) {
+               ao2_lock(p);
                ast_set_flag(p, LOCAL_LAUNCHED_PBX);
+               ao2_unlock(p);
+       }
 
-       ao2_unlock(p);
-       ast_channel_unlock(p->chan);
+return_cleanup:
+       ast_channel_unref(chan);
        ao2_ref(p, -1);
        return res;
 }