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Convert device state callbacks to ao2 objects to fix a deadlock in chan_sip.

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Lock scenario presented here:
Thread 1
 holds ast_rdlock_contexts &conlock
 holds handle_statechange hints
 holds handle_statechange hint
  waiting for cb_extensionstate
   Locked Here: chan_sip.c line 7428 (find_call)
Thread 2
 holds handle_request_do &netlock
 holds find_call sip_pvt_ptr
  waiting for ast_rdlock_contexts &conlock
   Locked Here: pbx.c line 9911 (ast_rdlock_contexts)

Chan_sip has an established locking order of locking the sip_pvt and then
getting the context lock. So the as stated by the summary, the operations in
thread 2 have been modified to no longer require the context lock.

(closes issue #18310)
Reported by: one47
Patches: 
      statecbs_ao2.mk2.patch uploaded by one47 (license 23),
      modified by me

Review: https://reviewboard.asterisk.org/r/1072/


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.6.2@302265 65c4cc65-6c06-0410-ace0-fbb531ad65f3
1.6.2
Jeff Peeler 15 years ago
parent f78288c30b
commit 7ca6a0e2bd
1 changed files with 86 additions and 74 deletions
Show Stats Download Patch File Download Diff File

160
main/pbx.c
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@ -886,7 +886,7 @@ struct ast_state_cb {
struct ast_hint {
struct ast_exten *exten; /*!< Extension */
int laststate; /*!< Last known state */
AST_LIST_HEAD_NOLOCK(, ast_state_cb) callbacks; /*!< Callback list for this extension */
struct ao2_container *callbacks; /*!< Callback container for this extension */
};
/* --- Hash tables of various objects --------*/
@ -1145,8 +1145,7 @@ static int stateid = 1;
*/
static struct ao2_container *hints;
/* XXX TODO Convert this to an astobj2 container, too. */
static AST_LIST_HEAD_NOLOCK_STATIC(statecbs, ast_state_cb);
static struct ao2_container *statecbs;
#ifdef CONTEXT_DEBUG
@ -3874,15 +3873,15 @@ static int handle_statechange(void *datap)
struct ast_str *str;
struct statechange *sc = datap;
struct ao2_iterator i;
struct ao2_iterator cb_iter;
if (!(str = ast_str_create(1024))) {
return -1;
}
i = ao2_iterator_init(hints, 0);
for (hint = ao2_iterator_next(&i); hint; ao2_ref(hint, -1), hint = ao2_iterator_next(&i)) {
struct ast_state_cb *cblist;
struct ast_state_cb *state_cb;
char *cur, *parse;
int state;
@ -3908,7 +3907,6 @@ static int handle_statechange(void *datap)
/* Device state changed since last check - notify the watchers */
ast_rdlock_contexts();
ao2_lock(hints);
ao2_lock(hint);
@ -3916,24 +3914,26 @@ static int handle_statechange(void *datap)
/* the extension has been destroyed */
ao2_unlock(hint);
ao2_unlock(hints);
ast_unlock_contexts();
continue;
}
/* For general callbacks */
AST_LIST_TRAVERSE(&statecbs, cblist, entry) {
cblist->callback(hint->exten->parent->name, hint->exten->exten, state, cblist->data);
cb_iter = ao2_iterator_init(statecbs, 0);
for (state_cb = ao2_iterator_next(&cb_iter); state_cb; ao2_ref(state_cb, -1), state_cb = ao2_iterator_next(&cb_iter)) {
state_cb->callback(hint->exten->parent->name, hint->exten->exten, state, state_cb->data);
}
ao2_iterator_destroy(&cb_iter);
/* For extension callbacks */
AST_LIST_TRAVERSE(&hint->callbacks, cblist, entry) {
cblist->callback(hint->exten->parent->name, hint->exten->exten, state, cblist->data);
cb_iter = ao2_iterator_init(hint->callbacks, 0);
for (state_cb = ao2_iterator_next(&cb_iter); state_cb; ao2_ref(state_cb, -1), state_cb = ao2_iterator_next(&cb_iter)) {
state_cb->callback(hint->exten->parent->name, hint->exten->exten, state, state_cb->data);
}
ao2_iterator_destroy(&cb_iter);
hint->laststate = state; /* record we saw the change */
ao2_unlock(hint);
ao2_unlock(hints);
ast_unlock_contexts();
}
ao2_iterator_destroy(&i);
ast_free(str);
@ -3946,31 +3946,32 @@ int ast_extension_state_add(const char *context, const char *exten,
ast_state_cb_type callback, void *data)
{
struct ast_hint *hint;
struct ast_state_cb *cblist;
struct ast_state_cb *state_cb;
struct ast_exten *e;
/* If there's no context and extension: add callback to statecbs list */
if (!context && !exten) {
ao2_lock(hints);
AST_LIST_TRAVERSE(&statecbs, cblist, entry) {
if (cblist->callback == callback) {
cblist->data = data;
ao2_unlock(hints);
return 0;
}
state_cb = ao2_find(statecbs, callback, 0);
if (state_cb) {
state_cb->data = data;
ao2_ref(state_cb, -1);
ao2_unlock(hints);
return 0;
}
/* Now insert the callback */
if (!(cblist = ast_calloc(1, sizeof(*cblist)))) {
if (!(state_cb = ao2_alloc(sizeof(*state_cb), NULL))) {
ao2_unlock(hints);
return -1;
}
cblist->id = 0;
cblist->callback = callback;
cblist->data = data;
state_cb->id = 0;
state_cb->callback = callback;
state_cb->data = data;
AST_LIST_INSERT_HEAD(&statecbs, cblist, entry);
ao2_link(statecbs, state_cb);
ao2_ref(state_cb, -1);
ao2_unlock(hints);
return 0;
@ -4007,35 +4008,35 @@ int ast_extension_state_add(const char *context, const char *exten,
}
/* Now insert the callback in the callback list */
if (!(cblist = ast_calloc(1, sizeof(*cblist)))) {
if (!(state_cb = ao2_alloc(sizeof(*state_cb), NULL))) {
ao2_ref(hint, -1);
return -1;
}
cblist->id = stateid++; /* Unique ID for this callback */
cblist->callback = callback; /* Pointer to callback routine */
cblist->data = data; /* Data for the callback */
state_cb->id = stateid++; /* Unique ID for this callback */
state_cb->callback = callback; /* Pointer to callback routine */
state_cb->data = data; /* Data for the callback */
ao2_lock(hint);
AST_LIST_INSERT_HEAD(&hint->callbacks, cblist, entry);
ao2_link(hint->callbacks, state_cb);
ao2_ref(state_cb, -1);
ao2_unlock(hint);
ao2_ref(hint, -1);
return cblist->id;
return state_cb->id;
}
/*! \brief Remove a watcher from the callback list */
static int find_hint_by_cb_id(void *obj, void *arg, int flags)
{
struct ast_state_cb *state_cb;
const struct ast_hint *hint = obj;
int *id = arg;
struct ast_state_cb *cb;
AST_LIST_TRAVERSE(&hint->callbacks, cb, entry) {
if (cb->id == *id) {
return CMP_MATCH | CMP_STOP;
}
if ((state_cb = ao2_find(hint->callbacks, id, 0))) {
ao2_ref(state_cb, -1);
return CMP_MATCH | CMP_STOP;
}
return 0;
@ -4053,13 +4054,11 @@ int ast_extension_state_del(int id, ast_state_cb_type callback)
if (!id) { /* id == 0 is a callback without extension */
ao2_lock(hints);
AST_LIST_TRAVERSE_SAFE_BEGIN(&statecbs, p_cur, entry) {
if (p_cur->callback == callback) {
AST_LIST_REMOVE_CURRENT(entry);
break;
}
p_cur = ao2_find(statecbs, callback, OBJ_UNLINK);
if (p_cur) {
ret = 0;
ao2_ref(p_cur, -1);
}
AST_LIST_TRAVERSE_SAFE_END;
ao2_unlock(hints);
} else { /* callback with extension, find the callback based on ID */
struct ast_hint *hint;
@ -4068,28 +4067,28 @@ int ast_extension_state_del(int id, ast_state_cb_type callback)
if (hint) {
ao2_lock(hint);
AST_LIST_TRAVERSE_SAFE_BEGIN(&hint->callbacks, p_cur, entry) {
if (p_cur->id == id) {
AST_LIST_REMOVE_CURRENT(entry);
ret = 0;
break;
}
p_cur = ao2_find(hint->callbacks, &id, OBJ_UNLINK);
if (p_cur) {
ret = 0;
ao2_ref(p_cur, -1);
}
AST_LIST_TRAVERSE_SAFE_END;
ao2_unlock(hint);
ao2_ref(hint, -1);
}
}
if (p_cur) {
ast_free(p_cur);
}
return ret;
}
static int hint_id_cmp(void *obj, void *arg, int flags)
{
const struct ast_state_cb *cb = obj;
int *id = arg;
return (cb->id == *id) ? CMP_MATCH | CMP_STOP : 0;
}
/*! \brief Add hint to hint list, check initial extension state */
static int ast_add_hint(struct ast_exten *e)
{
@ -4112,6 +4111,9 @@ static int ast_add_hint(struct ast_exten *e)
if (!(hint = ao2_alloc(sizeof(*hint), NULL))) {
return -1;
}
if (!(hint->callbacks = ao2_container_alloc(1, NULL, hint_id_cmp))) {
return -1;
}
/* Initialize and insert new item at the top */
hint->exten = e;
@ -4148,7 +4150,7 @@ static int ast_remove_hint(struct ast_exten *e)
{
/* Cleanup the Notifys if hint is removed */
struct ast_hint *hint;
struct ast_state_cb *cblist;
struct ast_state_cb *state_cb;
if (!e) {
return -1;
@ -4161,15 +4163,16 @@ static int ast_remove_hint(struct ast_exten *e)
}
ao2_lock(hint);
while ((cblist = AST_LIST_REMOVE_HEAD(&hint->callbacks, entry))) {
while ((state_cb = ao2_callback(hint->callbacks, OBJ_UNLINK, NULL, NULL))) {
/* Notify with -1 and remove all callbacks */
cblist->callback(hint->exten->parent->name, hint->exten->exten,
AST_EXTENSION_DEACTIVATED, cblist->data);
ast_free(cblist);
state_cb->callback(hint->exten->parent->name, hint->exten->exten,
AST_EXTENSION_DEACTIVATED, state_cb->data);
ao2_ref(state_cb, -1);
}
hint->exten = NULL;
ao2_unlink(hints, hint);
ao2_ref(hint->callbacks, -1);
ao2_unlock(hint);
ao2_ref(hint, -1);
@ -5383,7 +5386,6 @@ static char *handle_show_hints(struct ast_cli_entry *e, int cmd, struct ast_cli_
struct ast_hint *hint;
int num = 0;
int watchers;
struct ast_state_cb *watcher;
struct ao2_iterator i;
switch (cmd) {
@ -5407,10 +5409,7 @@ static char *handle_show_hints(struct ast_cli_entry *e, int cmd, struct ast_cli_
i = ao2_iterator_init(hints, 0);
for (hint = ao2_iterator_next(&i); hint; ao2_ref(hint, -1), hint = ao2_iterator_next(&i)) {
watchers = 0;
AST_LIST_TRAVERSE(&hint->callbacks, watcher, entry) {
watchers++;
}
watchers = ao2_container_count(hint->callbacks);
ast_cli(a->fd, " %20s@%-20.20s: %-20.20s State:%-15.15s Watchers %2d\n",
ast_get_extension_name(hint->exten),
ast_get_context_name(ast_get_extension_context(hint->exten)),
@ -5460,7 +5459,6 @@ static char *handle_show_hint(struct ast_cli_entry *e, int cmd, struct ast_cli_a
struct ast_hint *hint;
int watchers;
int num = 0, extenlen;
struct ast_state_cb *watcher;
struct ao2_iterator i;
switch (cmd) {
@ -5487,10 +5485,7 @@ static char *handle_show_hint(struct ast_cli_entry *e, int cmd, struct ast_cli_a
for (hint = ao2_iterator_next(&i); hint; ao2_unlock(hint), ao2_ref(hint, -1), hint = ao2_iterator_next(&i)) {
ao2_lock(hint);
if (!strncasecmp(hint->exten ? ast_get_extension_name(hint->exten) : "", a->argv[3], extenlen)) {
watchers = 0;
AST_LIST_TRAVERSE(&hint->callbacks, watcher, entry) {
watchers++;
}
watchers = ao2_container_count(hint->callbacks);
ast_cli(a->fd, " %20s@%-20.20s: %-20.20s State:%-15.15s Watchers %2d\n",
ast_get_extension_name(hint->exten),
ast_get_context_name(ast_get_extension_context(hint->exten)),
@ -6722,7 +6717,8 @@ void ast_merge_contexts_and_delete(struct ast_context **extcontexts, struct ast_
/* preserve all watchers for hints */
i = ao2_iterator_init(hints, AO2_ITERATOR_DONTLOCK);
for (hint = ao2_iterator_next(&i); hint; ao2_ref(hint, -1), hint = ao2_iterator_next(&i)) {
if (!AST_LIST_EMPTY(&hint->callbacks)) {
if (ao2_container_count(hint->callbacks)) {
length = strlen(hint->exten->exten) + strlen(hint->exten->parent->name) + 2 + sizeof(*this);
if (!(this = ast_calloc(1, length))) {
continue;
@ -6734,8 +6730,12 @@ void ast_merge_contexts_and_delete(struct ast_context **extcontexts, struct ast_
continue;
}
/* this removes all the callbacks from the hint into this. */
AST_LIST_APPEND_LIST(&this->callbacks, &hint->callbacks, entry);
/* this removes all the callbacks from the hint into 'this'. */
while ((thiscb = ao2_callback(hint->callbacks, OBJ_UNLINK, NULL, NULL))) {
AST_LIST_INSERT_TAIL(&this->callbacks, thiscb, entry);
/* We intentionally do not unref thiscb to account for the non-ao2 reference in this->callbacks */
}
this->laststate = hint->laststate;
this->context = this->data;
strcpy(this->data, hint->exten->parent->name);
@ -6777,11 +6777,14 @@ void ast_merge_contexts_and_delete(struct ast_context **extcontexts, struct ast_
/* this hint has been removed, notify the watchers */
while ((thiscb = AST_LIST_REMOVE_HEAD(&this->callbacks, entry))) {
thiscb->callback(this->context, this->exten, AST_EXTENSION_REMOVED, thiscb->data);
ast_free(thiscb);
ao2_ref(thiscb, -1); /* Ref that we added when putting into this->callbacks */
}
} else {
ao2_lock(hint);
AST_LIST_APPEND_LIST(&hint->callbacks, &this->callbacks, entry);
while ((thiscb = AST_LIST_REMOVE_HEAD(&this->callbacks, entry))) {
ao2_link(hint->callbacks, thiscb);
ao2_ref(thiscb, -1); /* Ref that we added when putting into this->callbacks */
}
hint->laststate = this->laststate;
ao2_unlock(hint);
}
@ -9725,9 +9728,18 @@ static int hint_cmp(void *obj, void *arg, int flags)
return (hint->exten == exten) ? CMP_MATCH | CMP_STOP : 0;
}
static int statecbs_cmp(void *obj, void *arg, int flags)
{
const struct ast_state_cb *state_cb = obj;
const struct ast_state_cb *callback = arg;
return (state_cb == callback) ? CMP_MATCH | CMP_STOP : 0;
}
int ast_pbx_init(void)
{
hints = ao2_container_alloc(HASH_EXTENHINT_SIZE, hint_hash, hint_cmp);
statecbs = ao2_container_alloc(HASH_EXTENHINT_SIZE, NULL, statecbs_cmp);
return hints ? 0 : -1;
return (hints && statecbs) ? 0 : -1;
}

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