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Commit 67c79c32 authored by Richard Mudgett's avatar Richard Mudgett
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chan_sip.c: Fix provisional_keepalive_sched_id deadlock. 

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

Change-Id: I98a694fd42bc81436c83aa92de03226e6e4e3f48
parent 76be7093
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with 79 additions and 26 deletions
channels/chan_sip.c
+ 79
− 26
View file @ 67c79c32
......@@ -1510,6 +1510,9 @@ 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. */
static void stop_provisional_keepalive(struct sip_pvt *pvt);
/*! \brief Definition of this channel for PBX channel registration */
struct ast_channel_tech sip_tech = {
.type = "SIP",
......@@ -4511,25 +4514,14 @@ static void add_blank(struct sip_request *req)
}
}
 
/* Run by the sched thread. */
static int send_provisional_keepalive_full(struct sip_pvt *pvt, int with_sdp)
{
const char *msg = NULL;
struct ast_channel *chan;
int res = 0;
int old_sched_id = pvt->provisional_keepalive_sched_id;
 
chan = sip_pvt_lock_full(pvt);
/* Check that nothing has changed while we were waiting for the lock */
if (old_sched_id != pvt->provisional_keepalive_sched_id) {
/* Keepalive has been cancelled or rescheduled, clean up and leave */
if (chan) {
ast_channel_unlock(chan);
chan = ast_channel_unref(chan);
}
sip_pvt_unlock(pvt);
dialog_unref(pvt, "dialog ref for provisional keepalive");
return 0;
}
 
if (!pvt->last_provisional || !strncasecmp(pvt->last_provisional, "100", 3)) {
msg = "183 Session Progress";
......@@ -4542,25 +4534,23 @@ static int send_provisional_keepalive_full(struct sip_pvt *pvt, int with_sdp)
transmit_response(pvt, S_OR(msg, pvt->last_provisional), &pvt->initreq);
}
res = PROVIS_KEEPALIVE_TIMEOUT;
} else {
pvt->provisional_keepalive_sched_id = -1;
}
 
sip_pvt_unlock(pvt);
if (chan) {
ast_channel_unlock(chan);
chan = ast_channel_unref(chan);
}
if (!res) {
pvt->provisional_keepalive_sched_id = -1;
ast_channel_unref(chan);
}
 
sip_pvt_unlock(pvt);
if (!res) {
dialog_unref(pvt, "dialog ref for provisional keepalive");
dialog_unref(pvt, "Schedule provisional keepalive complete");
}
return res;
}
 
/* Run by the sched thread. */
static int send_provisional_keepalive(const void *data)
{
struct sip_pvt *pvt = (struct sip_pvt *) data;
......@@ -4568,6 +4558,7 @@ static int send_provisional_keepalive(const void *data)
return send_provisional_keepalive_full(pvt, 0);
}
 
/* Run by the sched thread. */
static int send_provisional_keepalive_with_sdp(const void *data)
{
struct sip_pvt *pvt = (void *) data;
......@@ -4575,12 +4566,73 @@ static int send_provisional_keepalive_with_sdp(const void *data)
return send_provisional_keepalive_full(pvt, 1);
}
 
/* Run by the sched thread. */
static int __update_provisional_keepalive_full(struct sip_pvt *pvt, int with_sdp)
{
AST_SCHED_DEL_UNREF(sched, pvt->provisional_keepalive_sched_id,
dialog_unref(pvt, "Stop scheduled provisional keepalive for update"));
sip_pvt_lock(pvt);
if (pvt->invitestate < INV_COMPLETED) {
/* Provisional keepalive is still needed. */
dialog_ref(pvt, "Schedule provisional keepalive");
pvt->provisional_keepalive_sched_id = ast_sched_add(sched, PROVIS_KEEPALIVE_TIMEOUT,
with_sdp ? send_provisional_keepalive_with_sdp : send_provisional_keepalive,
pvt);
if (pvt->provisional_keepalive_sched_id < 0) {
dialog_unref(pvt, "Failed to schedule provisional keepalive");
}
}
sip_pvt_unlock(pvt);
dialog_unref(pvt, "Update provisional keepalive action");
return 0;
}
/* Run by the sched thread. */
static int __update_provisional_keepalive(const void *data)
{
struct sip_pvt *pvt = (void *) data;
return __update_provisional_keepalive_full(pvt, 0);
}
/* Run by the sched thread. */
static int __update_provisional_keepalive_with_sdp(const void *data)
{
struct sip_pvt *pvt = (void *) data;
return __update_provisional_keepalive_full(pvt, 1);
}
static void update_provisional_keepalive(struct sip_pvt *pvt, int with_sdp)
{
AST_SCHED_DEL_UNREF(sched, pvt->provisional_keepalive_sched_id, dialog_unref(pvt, "when you delete the provisional_keepalive_sched_id, you should dec the refcount for the stored dialog ptr"));
dialog_ref(pvt, "Update provisional keepalive action");
if (ast_sched_add(sched, 0,
with_sdp ? __update_provisional_keepalive_with_sdp : __update_provisional_keepalive,
pvt) < 0) {
dialog_unref(pvt, "Failed to schedule update provisional keepalive action");
}
}
/* Run by the sched thread. */
static int __stop_provisional_keepalive(const void *data)
{
struct sip_pvt *pvt = (void *) data;
 
pvt->provisional_keepalive_sched_id = ast_sched_add(sched, PROVIS_KEEPALIVE_TIMEOUT,
with_sdp ? send_provisional_keepalive_with_sdp : send_provisional_keepalive, dialog_ref(pvt, "Increment refcount to pass dialog pointer to sched callback"));
AST_SCHED_DEL_UNREF(sched, pvt->provisional_keepalive_sched_id,
dialog_unref(pvt, "Stop scheduled provisional keepalive"));
dialog_unref(pvt, "Stop provisional keepalive action");
return 0;
}
static void stop_provisional_keepalive(struct sip_pvt *pvt)
{
dialog_ref(pvt, "Stop provisional keepalive action");
if (ast_sched_add(sched, 0, __stop_provisional_keepalive, pvt) < 0) {
/* Uh Oh. Expect bad behavior. */
dialog_unref(pvt, "Failed to schedule stop provisional keepalive action");
}
}
 
static void add_required_respheader(struct sip_request *req)
......@@ -4636,7 +4688,7 @@ static int send_response(struct sip_pvt *p, struct sip_request *req, enum xmitty
 
/* If we are sending a final response to an INVITE, stop retransmitting provisional responses */
if (p->initreq.method == SIP_INVITE && reliable == XMIT_CRITICAL) {
AST_SCHED_DEL_UNREF(sched, p->provisional_keepalive_sched_id, dialog_unref(p, "when you delete the provisional_keepalive_sched_id, you should dec the refcount for the stored dialog ptr"));
stop_provisional_keepalive(p);
}
 
res = (reliable) ?
......@@ -7044,7 +7096,8 @@ static int sip_hangup(struct ast_channel *ast)
}
} else { /* Incoming call, not up */
const char *res;
AST_SCHED_DEL_UNREF(sched, p->provisional_keepalive_sched_id, dialog_unref(p, "when you delete the provisional_keepalive_sched_id, you should dec the refcount for the stored dialog ptr"));
stop_provisional_keepalive(p);
if (p->hangupcause && (res = hangup_cause2sip(p->hangupcause)))
transmit_response_reliable(p, res, &p->initreq);
else
......@@ -9094,7 +9147,7 @@ static void forked_invite_init(struct sip_request *req, const char *new_theirtag
* \post pvt is locked
* \post pvt->owner is locked and its reference count is increased (if pvt->owner is not NULL)
*
* \returns a pointer to the locked and reffed pvt->owner channel if it exists.
* \return a pointer to the locked and reffed pvt->owner channel if it exists.
*/
static struct ast_channel *sip_pvt_lock_full(struct sip_pvt *pvt)
{
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