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chan_sip.c: Fix session timers 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

Change-Id: I6d65269151ba95e0d8fe4e9e611881cde2ab4900
This commit is contained in:
Richard Mudgett
2016-03-08 15:08:19 -06:00
parent 69810b306d
commit 02458cc6fd
2 changed files with 132 additions and 114 deletions
Download Patch File Download Diff File Expand all files Collapse all files

245
channels/chan_sip.c
View File

@@ -1488,7 +1488,6 @@ static void change_t38_state(struct sip_pvt *p, int state);
/*------ Session-Timers functions --------- */
static void proc_422_rsp(struct sip_pvt *p, struct sip_request *rsp);
static int proc_session_timer(const void *vp);
static void stop_session_timer(struct sip_pvt *p);
static void start_session_timer(struct sip_pvt *p);
static void restart_session_timer(struct sip_pvt *p);
@@ -1512,6 +1511,7 @@ 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);
static void do_stop_session_timer(struct sip_pvt *pvt);
/*! \brief Definition of this channel for PBX channel registration */
struct ast_channel_tech sip_tech = {
@@ -3288,7 +3288,8 @@ static void do_dialog_unlink_sched_items(struct sip_pvt *dialog)
dialog_unref(dialog, "Stop scheduled t38id"));
if (dialog->stimer) {
stop_session_timer(dialog);
dialog->stimer->st_active = FALSE;
do_stop_session_timer(dialog);
}
}
@@ -6529,12 +6530,8 @@ static void sip_pvt_dtor(void *vdoomed)
ast_debug(3, "Destroying SIP dialog %s\n", p->callid);
/* Destroy Session-Timers if allocated */
if (p->stimer) {
p->stimer->quit_flag = 1;
stop_session_timer(p);
ast_free(p->stimer);
p->stimer = NULL;
}
ast_free(p->stimer);
p->stimer = NULL;
if (sip_debug_test_pvt(p))
ast_verbose("Really destroying SIP dialog '%s' Method: %s\n", p->callid, sip_methods[p->method].text);
@@ -7166,7 +7163,7 @@ static int sip_hangup(struct ast_channel *ast)
p->invitestate = INV_TERMINATED;
}
} else { /* Call is in UP state, send BYE */
if (p->stimer->st_active == TRUE) {
if (p->stimer) {
stop_session_timer(p);
}
@@ -7339,8 +7336,8 @@ static int sip_answer(struct ast_channel *ast)
ast_set_flag(&p->flags[1], SIP_PAGE2_DIALOG_ESTABLISHED);
/* RFC says the session timer starts counting on 200,
* not on INVITE. */
if (p->stimer->st_active == TRUE) {
start_session_timer(p);
if (p->stimer) {
restart_session_timer(p);
}
}
sip_pvt_unlock(p);
@@ -8732,13 +8729,13 @@ static struct sip_st_dlg* sip_st_alloc(struct sip_pvt *const p)
return p->stimer;
}
if (!(stp = ast_calloc(1, sizeof(struct sip_st_dlg))))
if (!(stp = ast_calloc(1, sizeof(struct sip_st_dlg)))) {
return NULL;
}
stp->st_schedid = -1; /* Session-Timers ast_sched scheduler id */
p->stimer = stp;
stp->st_schedid = -1; /* Session-Timers ast_sched scheduler id */
return p->stimer;
}
@@ -25991,7 +25988,7 @@ static int handle_request_invite(struct sip_pvt *p, struct sip_request *req, str
/* Check if OLI/ANI-II is present in From: */
parse_oli(req, p->owner);
if (reinvite && p->stimer->st_active == TRUE) {
if (reinvite && p->stimer) {
restart_session_timer(p);
}
@@ -29216,42 +29213,111 @@ static void acl_change_stasis_cb(void *data, struct stasis_subscription *sub,
restart_monitor();
}
/*! \brief Session-Timers: Restart session timer */
static void restart_session_timer(struct sip_pvt *p)
/*!
* \brief Session-Timers: Process session refresh timeout event
*
* \note Run by the sched thread.
*/
static int proc_session_timer(const void *vp)
{
if (p->stimer->st_active == TRUE) {
ast_debug(2, "Session timer stopped: %d - %s\n", p->stimer->st_schedid, p->callid);
AST_SCHED_DEL_UNREF(sched, p->stimer->st_schedid,
dialog_unref(p, "Removing session timer ref"));
start_session_timer(p);
struct sip_pvt *p = (struct sip_pvt *) vp;
struct sip_st_dlg *stimer = p->stimer;
int res = 0;
ast_assert(stimer != NULL);
ast_debug(2, "Session timer expired: %d - %s\n", stimer->st_schedid, p->callid);
if (!p->owner) {
goto return_unref;
}
if ((stimer->st_active != TRUE) || (ast_channel_state(p->owner) != AST_STATE_UP)) {
goto return_unref;
}
if (stimer->st_ref == SESSION_TIMER_REFRESHER_US) {
res = 1;
if (T38_ENABLED == p->t38.state) {
transmit_reinvite_with_sdp(p, TRUE, TRUE);
} else {
transmit_reinvite_with_sdp(p, FALSE, TRUE);
}
} else {
struct ast_channel *owner;
ast_log(LOG_WARNING, "Session-Timer expired - %s\n", p->callid);
owner = sip_pvt_lock_full(p);
if (owner) {
send_session_timeout(owner, "SIPSessionTimer");
ast_softhangup_nolock(owner, AST_SOFTHANGUP_DEV);
ast_channel_unlock(owner);
ast_channel_unref(owner);
}
sip_pvt_unlock(p);
}
return_unref:
if (!res) {
/* Session timer processing is no longer needed. */
ast_debug(2, "Session timer stopped: %d - %s\n",
stimer->st_schedid, p->callid);
/* Don't pass go, don't collect $200.. we are the scheduled
* callback. We can rip ourself out here. */
stimer->st_schedid = -1;
stimer->st_active = FALSE;
/* If we are not asking to be rescheduled, then we need to release our
* reference to the dialog. */
dialog_unref(p, "Session timer st_schedid complete");
}
return res;
}
static void do_stop_session_timer(struct sip_pvt *pvt)
{
struct sip_st_dlg *stimer = pvt->stimer;
if (-1 < stimer->st_schedid) {
ast_debug(2, "Session timer stopped: %d - %s\n",
stimer->st_schedid, pvt->callid);
AST_SCHED_DEL_UNREF(sched, stimer->st_schedid,
dialog_unref(pvt, "Stop scheduled session timer st_schedid"));
}
}
/* Run by the sched thread. */
static int __stop_session_timer(const void *data)
{
struct sip_pvt *pvt = (void *) data;
do_stop_session_timer(pvt);
dialog_unref(pvt, "Stop session timer action");
return 0;
}
/*! \brief Session-Timers: Stop session timer */
static void stop_session_timer(struct sip_pvt *p)
static void stop_session_timer(struct sip_pvt *pvt)
{
if (p->stimer->st_active == TRUE) {
p->stimer->st_active = FALSE;
ast_debug(2, "Session timer stopped: %d - %s\n", p->stimer->st_schedid, p->callid);
AST_SCHED_DEL_UNREF(sched, p->stimer->st_schedid,
dialog_unref(p, "removing session timer ref"));
struct sip_st_dlg *stimer = pvt->stimer;
stimer->st_active = FALSE;
dialog_ref(pvt, "Stop session timer action");
if (ast_sched_add(sched, 0, __stop_session_timer, pvt) < 0) {
/* Uh Oh. Expect bad behavior. */
dialog_unref(pvt, "Failed to schedule stop session timer action");
}
}
/*! \brief Session-Timers: Start session timer */
static void start_session_timer(struct sip_pvt *p)
/* Run by the sched thread. */
static int __start_session_timer(const void *data)
{
struct sip_pvt *pvt = (void *) data;
struct sip_st_dlg *stimer = pvt->stimer;
unsigned int timeout_ms;
if (p->stimer->st_schedid > -1) {
/* in the event a timer is already going, stop it */
ast_debug(2, "Session timer stopped: %d - %s\n", p->stimer->st_schedid, p->callid);
AST_SCHED_DEL_UNREF(sched, p->stimer->st_schedid,
dialog_unref(p, "unref stimer->st_schedid from dialog"));
}
/*
* RFC 4028 Section 10
* If the side not performing refreshes does not receive a
@@ -29261,96 +29327,49 @@ static void start_session_timer(struct sip_pvt *p)
* interval is RECOMMENDED.
*/
timeout_ms = (1000 * p->stimer->st_interval);
if (p->stimer->st_ref == SESSION_TIMER_REFRESHER_US) {
timeout_ms = (1000 * stimer->st_interval);
if (stimer->st_ref == SESSION_TIMER_REFRESHER_US) {
timeout_ms /= 2;
} else {
timeout_ms -= MIN(timeout_ms / 3, 32000);
}
p->stimer->st_schedid = ast_sched_add(sched, timeout_ms, proc_session_timer,
dialog_ref(p, "adding session timer ref"));
/* in the event a timer is already going, stop it */
do_stop_session_timer(pvt);
if (p->stimer->st_schedid < 0) {
dialog_unref(p, "removing session timer ref");
ast_log(LOG_ERROR, "ast_sched_add failed - %s\n", p->callid);
dialog_ref(pvt, "Schedule session timer st_schedid");
stimer->st_schedid = ast_sched_add(sched, timeout_ms, proc_session_timer, pvt);
if (stimer->st_schedid < 0) {
dialog_unref(pvt, "Failed to schedule session timer st_schedid");
} else {
p->stimer->st_active = TRUE;
ast_debug(2, "Session timer started: %d - %s %ums\n", p->stimer->st_schedid, p->callid, timeout_ms);
ast_debug(2, "Session timer started: %d - %s %ums\n",
stimer->st_schedid, pvt->callid, timeout_ms);
}
dialog_unref(pvt, "Start session timer action");
return 0;
}
/*! \brief Session-Timers: Process session refresh timeout event */
static int proc_session_timer(const void *vp)
/*! \brief Session-Timers: Start session timer */
static void start_session_timer(struct sip_pvt *pvt)
{
struct sip_pvt *p = (struct sip_pvt *) vp;
int res = 0;
struct sip_st_dlg *stimer = pvt->stimer;
if (!p->stimer) {
ast_log(LOG_WARNING, "Null stimer in proc_session_timer - %s\n", p->callid);
goto return_unref;
stimer->st_active = TRUE;
dialog_ref(pvt, "Start session timer action");
if (ast_sched_add(sched, 0, __start_session_timer, pvt) < 0) {
/* Uh Oh. Expect bad behavior. */
dialog_unref(pvt, "Failed to schedule start session timer action");
}
ast_debug(2, "Session timer expired: %d - %s\n", p->stimer->st_schedid, p->callid);
if (!p->owner) {
goto return_unref;
}
if ((p->stimer->st_active != TRUE) || (ast_channel_state(p->owner) != AST_STATE_UP)) {
goto return_unref;
}
if (p->stimer->st_ref == SESSION_TIMER_REFRESHER_US) {
res = 1;
if (T38_ENABLED == p->t38.state) {
transmit_reinvite_with_sdp(p, TRUE, TRUE);
} else {
transmit_reinvite_with_sdp(p, FALSE, TRUE);
}
} else {
if (p->stimer->quit_flag) {
goto return_unref;
}
ast_log(LOG_WARNING, "Session-Timer expired - %s\n", p->callid);
sip_pvt_lock(p);
while (p->owner && ast_channel_trylock(p->owner)) {
sip_pvt_unlock(p);
usleep(1);
if (p->stimer && p->stimer->quit_flag) {
goto return_unref;
}
sip_pvt_lock(p);
}
send_session_timeout(p->owner, "SIPSessionTimer");
ast_softhangup_nolock(p->owner, AST_SOFTHANGUP_DEV);
ast_channel_unlock(p->owner);
sip_pvt_unlock(p);
}
return_unref:
if (!res) {
/* An error occurred. Stop session timer processing */
if (p->stimer) {
ast_debug(2, "Session timer stopped: %d - %s\n", p->stimer->st_schedid, p->callid);
/* Don't pass go, don't collect $200.. we are the scheduled
* callback. We can rip ourself out here. */
p->stimer->st_schedid = -1;
/* Calling stop_session_timer is nice for consistent debug
* logs. */
stop_session_timer(p);
}
/* If we are not asking to be rescheduled, then we need to release our
* reference to the dialog. */
dialog_unref(p, "removing session timer ref");
}
return res;
}
/*! \brief Session-Timers: Restart session timer */
static void restart_session_timer(struct sip_pvt *p)
{
if (p->stimer->st_active == TRUE) {
start_session_timer(p);
}
}
/*! \brief Session-Timers: Function for parsing Min-SE header */
int parse_minse (const char *p_hdrval, int *const p_interval)

1
channels/sip/include/sip.h
View File

@@ -959,7 +959,6 @@ struct sip_st_dlg {
int st_cached_max_se; /*!< Session-Timers cached Session-Expires */
enum st_mode st_cached_mode; /*!< Session-Timers cached M.O. */
enum st_refresher st_cached_ref; /*!< Session-Timers session refresher */
unsigned char quit_flag:1; /*!< Stop trying to lock; just quit */
};