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ensure that hint watchers (subscribers) cannot be added or removed while the dialplan is being modified

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git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.2@16742 65c4cc65-6c06-0410-ace0-fbb531ad65f3
This commit is contained in:
Kevin P. Fleming
2006-03-31 18:24:22 +00:00
parent 65acfca5af
commit 6c0ac0721e
1 changed files with 21 additions and 6 deletions
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27
pbx.c
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@@ -514,6 +514,12 @@ AST_MUTEX_DEFINE_STATIC(applock); /* Lock for the application list */
struct ast_switch *switches = NULL;
AST_MUTEX_DEFINE_STATIC(switchlock); /* Lock for switches */
/* WARNING:
When holding this lock, do _not_ do anything that will cause conlock
to be taken, unless you _already_ hold it. The ast_merge_contexts_and_delete
function will take the locks in conlock/hintlock order, so any other
paths that require both locks must also take them in that order.
*/
AST_MUTEX_DEFINE_STATIC(hintlock); /* Lock for extension state notifys */
static int stateid = 1;
struct ast_hint *hints = NULL;
@@ -3696,9 +3702,20 @@ void ast_merge_contexts_and_delete(struct ast_context **extcontexts, const char
int length;
struct ast_state_cb *thiscb, *prevcb;
/* preserve all watchers for hints associated with this registrar */
AST_LIST_HEAD_INIT(&store);
/* it is very important that this function hold the hintlock _and_ the conlock
during its operation; not only do we need to ensure that the list of contexts
and extensions does not change, but also that no hint callbacks (watchers) are
added or removed during the merge/delete process
in addition, the locks _must_ be taken in this order, because there are already
other code paths that use this order
*/
ast_mutex_lock(&conlock);
ast_mutex_lock(&hintlock);
/* preserve all watchers for hints associated with this registrar */
for (hint = hints; hint; hint = hint->next) {
if (hint->callbacks && !strcmp(registrar, hint->exten->parent->registrar)) {
length = strlen(hint->exten->exten) + strlen(hint->exten->parent->name) + 2 + sizeof(*this);
@@ -3717,10 +3734,8 @@ void ast_merge_contexts_and_delete(struct ast_context **extcontexts, const char
AST_LIST_INSERT_HEAD(&store, this, list);
}
}
ast_mutex_unlock(&hintlock);
tmp = *extcontexts;
ast_mutex_lock(&conlock);
if (registrar) {
__ast_context_destroy(NULL,registrar);
while (tmp) {
@@ -3740,7 +3755,6 @@ void ast_merge_contexts_and_delete(struct ast_context **extcontexts, const char
*extcontexts = NULL;
} else
ast_log(LOG_WARNING, "Requested contexts didn't get merged\n");
ast_mutex_unlock(&conlock);
/* restore the watchers for hints that can be found; notify those that
cannot be restored
@@ -3748,7 +3762,6 @@ void ast_merge_contexts_and_delete(struct ast_context **extcontexts, const char
while ((this = AST_LIST_REMOVE_HEAD(&store, list))) {
exten = ast_hint_extension(NULL, this->context, this->exten);
/* Find the hint in the list of hints */
ast_mutex_lock(&hintlock);
for (hint = hints; hint; hint = hint->next) {
if (hint->exten == exten)
break;
@@ -3771,10 +3784,12 @@ void ast_merge_contexts_and_delete(struct ast_context **extcontexts, const char
hint->callbacks = this->callbacks;
hint->laststate = this->laststate;
}
ast_mutex_unlock(&hintlock);
free(this);
}
ast_mutex_unlock(&hintlock);
ast_mutex_unlock(&conlock);
return;
}