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Prevent BLF subscriptions from causing deadlocks

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Fix a locking inversion in sip_send_mwi_to_peer that was causing deadlocks.
This function now requires that both the peer and associated pvt be unlocked
before it is called for cases where peer and peer->mwipvt form a circular
reference.

(closes issue ASTERISK-18663)
Review: https://reviewboard.asterisk.org/r/1563/


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@343621 65c4cc65-6c06-0410-ace0-fbb531ad65f3
This commit is contained in:
Kinsey Moore
2011-11-07 20:27:38 +00:00
parent 3864c4083c
commit dc3ca68670
1 changed files with 33 additions and 10 deletions
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43
channels/chan_sip.c
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@@ -24345,7 +24345,9 @@ static int handle_request_subscribe(struct sip_pvt *p, struct sip_request *req,
p->subscribed = MWI_NOTIFICATION;
if (ast_test_flag(&authpeer->flags[1], SIP_PAGE2_SUBSCRIBEMWIONLY)) {
ao2_unlock(p);
add_peer_mwi_subs(authpeer);
ao2_lock(p);
}
if (authpeer->mwipvt && authpeer->mwipvt != p) { /* Destroy old PVT if this is a new one */
/* We only allow one subscription per peer */
@@ -24421,7 +24423,12 @@ static int handle_request_subscribe(struct sip_pvt *p, struct sip_request *req,
ast_set_flag(&p->flags[1], SIP_PAGE2_DIALOG_ESTABLISHED);
transmit_response(p, "200 OK", req);
if (p->relatedpeer) { /* Send first notification */
sip_send_mwi_to_peer(p->relatedpeer, 0);
struct sip_peer *peer = p->relatedpeer;
ref_peer(peer, "ensure a peer ref is held during MWI sending");
ao2_unlock(p);
sip_send_mwi_to_peer(peer, 0);
ao2_lock(p);
unref_peer(peer, "release a peer ref now that MWI is sent");
}
} else if (p->subscribed != CALL_COMPLETION) {
if ((firststate = ast_extension_state(NULL, p->context, p->exten)) < 0) {
@@ -25132,36 +25139,49 @@ static int get_cached_mwi(struct sip_peer *peer, int *new, int *old)
return in_cache;
}
/*! \brief Send message waiting indication to alert peer that they've got voicemail */
/*! \brief Send message waiting indication to alert peer that they've got voicemail
* \note Both peer and associated sip_pvt must be unlocked prior to calling this function
*/
static int sip_send_mwi_to_peer(struct sip_peer *peer, int cache_only)
{
/* Called with peerl lock, but releases it */
struct sip_pvt *p;
int newmsgs = 0, oldmsgs = 0;
const char *vmexten;
if (ast_test_flag((&peer->flags[1]), SIP_PAGE2_SUBSCRIBEMWIONLY) && !peer->mwipvt)
ao2_lock(peer);
vmexten = ast_strdupa(peer->vmexten);
if (ast_test_flag((&peer->flags[1]), SIP_PAGE2_SUBSCRIBEMWIONLY) && !peer->mwipvt) {
ao2_unlock(peer);
return 0;
}
/* Do we have an IP address? If not, skip this peer */
if (ast_sockaddr_isnull(&peer->addr) && ast_sockaddr_isnull(&peer->defaddr))
if (ast_sockaddr_isnull(&peer->addr) && ast_sockaddr_isnull(&peer->defaddr)) {
ao2_unlock(peer);
return 0;
}
/* Attempt to use cached mwi to get message counts. */
if (!get_cached_mwi(peer, &newmsgs, &oldmsgs) && !cache_only) {
/* Fall back to manually checking the mailbox if not cache_only and get_cached_mwi failed */
struct ast_str *mailbox_str = ast_str_alloca(512);
peer_mailboxes_to_str(&mailbox_str, peer);
ao2_unlock(peer);
ast_app_inboxcount(mailbox_str->str, &newmsgs, &oldmsgs);
ao2_lock(peer);
}
ao2_lock(peer);
if (peer->mwipvt) {
/* Base message on subscription */
p = dialog_ref(peer->mwipvt, "sip_send_mwi_to_peer: Setting dialog ptr p from peer->mwipvt-- should this be done?");
p = dialog_ref(peer->mwipvt, "sip_send_mwi_to_peer: Setting dialog ptr p from peer->mwipvt");
ao2_unlock(peer);
} else {
ao2_unlock(peer);
/* Build temporary dialog for this message */
if (!(p = sip_alloc(NULL, NULL, 0, SIP_NOTIFY, NULL))) {
ao2_unlock(peer);
return -1;
}
@@ -25175,7 +25195,6 @@ static int sip_send_mwi_to_peer(struct sip_peer *peer, int cache_only)
dialog_unlink_all(p);
dialog_unref(p, "unref dialog p just created via sip_alloc");
/* sip_destroy(p); */
ao2_unlock(peer);
return 0;
}
/* Recalculate our side, and recalculate Call ID */
@@ -25183,11 +25202,15 @@ static int sip_send_mwi_to_peer(struct sip_peer *peer, int cache_only)
build_via(p);
ao2_t_unlink(dialogs, p, "About to change the callid -- remove the old name");
build_callid_pvt(p);
ao2_lock(peer);
if (!ast_strlen_zero(peer->mwi_from)) {
ast_string_field_set(p, mwi_from, peer->mwi_from);
} else if (!ast_strlen_zero(default_mwi_from)) {
ast_string_field_set(p, mwi_from, default_mwi_from);
}
ao2_unlock(peer);
ao2_t_link(dialogs, p, "Linking in under new name");
/* Destroy this session after 32 secs */
sip_scheddestroy(p, DEFAULT_TRANS_TIMEOUT);
@@ -25200,10 +25223,10 @@ static int sip_send_mwi_to_peer(struct sip_peer *peer, int cache_only)
/* Send MWI */
ast_set_flag(&p->flags[0], SIP_OUTGOING);
/* the following will decrement the refcount on p as it finishes */
transmit_notify_with_mwi(p, newmsgs, oldmsgs, peer->vmexten);
transmit_notify_with_mwi(p, newmsgs, oldmsgs, vmexten);
sip_pvt_unlock(p);
dialog_unref(p, "unref dialog ptr p just before it goes out of scope at the end of sip_send_mwi_to_peer.");
ao2_unlock(peer);
return 0;
}