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chan_sip.c: Fix mwi resub deadlock potential.

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This patch is part of a series to resolve deadlocks in chan_sip.c.

Stopping a scheduled event can result in a deadlock if the scheduled event
is running when you try to stop the event.  If you hold a lock needed by
the scheduled event while trying to stop the scheduled event then a
deadlock can happen.  The general strategy for resolving the deadlock
potential is to push the actual starting and stopping of the scheduled
events off onto the scheduler/do_monitor() thread by scheduling an
immediate one shot scheduled event.  Some restructuring may be needed
because the code may assume that the start/stop of the scheduled events is
immediate.

ASTERISK-25023 #close

Change-Id: I96d429c57a48861fd8bde63dd93db4e92dc3adb6
This commit is contained in:
Richard Mudgett
2016-03-11 12:22:48 -06:00
parent 5f6627a8a4
commit de04308ae4
1 changed files with 92 additions and 33 deletions
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125
channels/chan_sip.c
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@@ -1501,9 +1501,7 @@ static int sip_set_rtp_peer(struct ast_channel *chan, struct ast_rtp_instance *i
/*!--- SIP MWI Subscription support */
static int sip_subscribe_mwi(const char *value, int lineno);
static void sip_subscribe_mwi_destroy(void *data);
static void sip_send_all_mwi_subscriptions(void);
static int sip_subscribe_mwi_do(const void *data);
static int __sip_subscribe_mwi_do(struct sip_subscription_mwi *mwi);
/* Scheduler id start/stop/reschedule functions. */
@@ -6511,12 +6509,12 @@ static void sip_registry_destroy(void *obj)
static void sip_subscribe_mwi_destroy(void *data)
{
struct sip_subscription_mwi *mwi = data;
if (mwi->call) {
mwi->call->mwi = NULL;
mwi->call = dialog_unref(mwi->call, "sip_subscription_mwi destruction");
}
AST_SCHED_DEL(sched, mwi->resub);
ast_string_field_free_memory(mwi);
}
@@ -14645,22 +14643,96 @@ static int transmit_invite(struct sip_pvt *p, int sipmethod, int sdp, int init,
return send_request(p, &req, init ? XMIT_CRITICAL : XMIT_RELIABLE, p->ocseq);
}
/*! \brief Send a subscription or resubscription for MWI */
/*!
* \brief Send a subscription or resubscription for MWI
*
* \note Run by the sched thread.
*/
static int sip_subscribe_mwi_do(const void *data)
{
struct sip_subscription_mwi *mwi = (struct sip_subscription_mwi*)data;
if (!mwi) {
return -1;
}
struct sip_subscription_mwi *mwi = (struct sip_subscription_mwi *) data;
mwi->resub = -1;
__sip_subscribe_mwi_do(mwi);
ao2_t_ref(mwi, -1, "unref mwi to balance ast_sched_add");
ao2_t_ref(mwi, -1, "Scheduled mwi resub complete");
return 0;
}
/* Run by the sched thread. */
static int __shutdown_mwi_subscription(const void *data)
{
struct sip_subscription_mwi *mwi = (void *) data;
AST_SCHED_DEL_UNREF(sched, mwi->resub,
ao2_t_ref(mwi, -1, "Stop scheduled mwi resub"));
if (mwi->dnsmgr) {
ast_dnsmgr_release(mwi->dnsmgr);
mwi->dnsmgr = NULL;
ao2_t_ref(mwi, -1, "dnsmgr release");
}
ao2_t_ref(mwi, -1, "Shutdown MWI subscription action");
return 0;
}
static void shutdown_mwi_subscription(struct sip_subscription_mwi *mwi)
{
ao2_t_ref(mwi, +1, "Shutdown MWI subscription action");
if (ast_sched_add(sched, 0, __shutdown_mwi_subscription, mwi) < 0) {
/* Uh Oh. Expect bad behavior. */
ao2_t_ref(mwi, -1, "Failed to schedule shutdown MWI subscription action");
}
}
struct mwi_subscription_data {
struct sip_subscription_mwi *mwi;
int ms;
};
/* Run by the sched thread. */
static int __start_mwi_subscription(const void *data)
{
struct mwi_subscription_data *sched_data = (void *) data;
struct sip_subscription_mwi *mwi = sched_data->mwi;
int ms = sched_data->ms;
ast_free(sched_data);
AST_SCHED_DEL_UNREF(sched, mwi->resub,
ao2_t_ref(mwi, -1, "Stop scheduled mwi resub"));
ao2_t_ref(mwi, +1, "Schedule mwi resub");
mwi->resub = ast_sched_add(sched, ms, sip_subscribe_mwi_do, mwi);
if (mwi->resub < 0) {
/* Uh Oh. Expect bad behavior. */
ao2_t_ref(mwi, -1, "Failed to schedule mwi resub");
}
ao2_t_ref(mwi, -1, "Start MWI subscription action");
return 0;
}
static void start_mwi_subscription(struct sip_subscription_mwi *mwi, int ms)
{
struct mwi_subscription_data *sched_data;
sched_data = ast_malloc(sizeof(*sched_data));
if (!sched_data) {
/* Uh Oh. Expect bad behavior. */
return;
}
sched_data->mwi = mwi;
sched_data->ms = ms;
ao2_t_ref(mwi, +1, "Start MWI subscription action");
if (ast_sched_add(sched, 0, __start_mwi_subscription, sched_data) < 0) {
/* Uh Oh. Expect bad behavior. */
ao2_t_ref(mwi, -1, "Failed to schedule start MWI subscription action");
ast_free(sched_data);
}
}
static void on_dns_update_registry(struct ast_sockaddr *old, struct ast_sockaddr *new, void *data)
{
struct sip_registry *reg = data;
@@ -17159,6 +17231,7 @@ static void acl_change_event_stasis_unsubscribe(void)
acl_change_sub = stasis_unsubscribe_and_join(acl_change_sub);
}
/* Run by the sched thread. */
static int network_change_sched_cb(const void *data)
{
network_change_sched_id = -1;
@@ -23986,9 +24059,7 @@ static void handle_response_subscribe(struct sip_pvt *p, int resp, const char *r
p->options = NULL;
}
p->mwi->subscribed = 1;
if ((p->mwi->resub = ast_sched_add(sched, mwi_expiry * 1000, sip_subscribe_mwi_do, ao2_t_bump(p->mwi, "mwi ast_sched_add"))) < 0) {
ao2_t_ref(p->mwi, -1, "mwi ast_sched_add < 0");
}
start_mwi_subscription(p->mwi, mwi_expiry * 1000);
break;
case 401:
case 407:
@@ -33560,18 +33631,12 @@ static void sip_send_all_registers(void)
static void sip_send_all_mwi_subscriptions(void)
{
struct ao2_iterator iter;
struct sip_subscription_mwi *iterator;
struct sip_subscription_mwi *mwi;
iter = ao2_iterator_init(subscription_mwi_list, 0);
while ((iterator = ao2_t_iterator_next(&iter, "sip_send_all_mwi_subscriptions iter"))) {
ao2_lock(iterator);
AST_SCHED_DEL(sched, iterator->resub);
ao2_t_ref(iterator, +1, "mwi added to schedule");
if ((iterator->resub = ast_sched_add(sched, 1, sip_subscribe_mwi_do, iterator)) < 0) {
ao2_t_ref(iterator, -1, "mwi failed to schedule");
}
ao2_unlock(iterator);
ao2_t_ref(iterator, -1, "sip_send_all_mwi_subscriptions iter");
while ((mwi = ao2_t_iterator_next(&iter, "sip_send_all_mwi_subscriptions iter"))) {
start_mwi_subscription(mwi, 1);
ao2_t_ref(mwi, -1, "sip_send_all_mwi_subscriptions iter");
}
ao2_iterator_destroy(&iter);
}
@@ -35233,18 +35298,12 @@ static int unload_module(void)
{
struct ao2_iterator iter;
struct sip_subscription_mwi *iterator;
struct sip_subscription_mwi *mwi;
iter = ao2_iterator_init(subscription_mwi_list, 0);
while ((iterator = ao2_t_iterator_next(&iter, "unload_module iter"))) {
ao2_lock(iterator);
if (iterator->dnsmgr) {
ast_dnsmgr_release(iterator->dnsmgr);
iterator->dnsmgr = NULL;
ao2_t_ref(iterator, -1, "dnsmgr release");
}
ao2_unlock(iterator);
ao2_t_ref(iterator, -1, "unload_module iter");
while ((mwi = ao2_t_iterator_next(&iter, "unload_module iter"))) {
shutdown_mwi_subscription(mwi);
ao2_t_ref(mwi, -1, "unload_module iter");
}
ao2_iterator_destroy(&iter);
}