From 2de95d53bc5f87f7a8ed0cb284229dca35bf4434 Mon Sep 17 00:00:00 2001
From: "Kevin P. Fleming" <kpfleming@digium.com>
Date: Fri, 31 Mar 2006 18:28:52 +0000
Subject: [PATCH] Merged revisions 16742 via svnmerge from
https://origsvn.digium.com/svn/asterisk/branches/1.2
........
r16742 | kpfleming | 2006-03-31 12:24:22 -0600 (Fri, 31 Mar 2006) | 2 lines
ensure that hint watchers (subscribers) cannot be added or removed while the dialplan is being modified
........
git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@16743 65c4cc65-6c06-0410-ace0-fbb531ad65f3
---
pbx.c | 27 +++++++++++++++++++++------
1 file changed, 21 insertions(+), 6 deletions(-)
diff --git a/pbx.c b/pbx.c
index 822155187f..2c478cad26 100644
--- a/pbx.c
+++ b/pbx.c
@@ -470,6 +470,12 @@ struct ast_switch *switches = NULL;
AST_MUTEX_DEFINE_STATIC(switchlock); /*!< Lock for switches */
static int stateid = 1;
+/* WARNING:
+ When holding this list's 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/hints order, so any other
+ paths that require both locks must also take them in that order.
+*/
static AST_LIST_HEAD_STATIC(hints, ast_hint);
struct ast_state_cb *statecbs = NULL;
@@ -3508,9 +3514,20 @@ 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 hint list lock _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_LIST_LOCK(&hints);
+
+ /* preserve all watchers for hints associated with this registrar */
AST_LIST_TRAVERSE(&hints, hint, list) {
if (hint->callbacks && !strcmp(registrar, hint->exten->parent->registrar)) {
length = strlen(hint->exten->exten) + strlen(hint->exten->parent->name) + 2 + sizeof(*this);
@@ -3526,10 +3543,8 @@ void ast_merge_contexts_and_delete(struct ast_context **extcontexts, const char
AST_LIST_INSERT_HEAD(&store, this, list);
}
}
- AST_LIST_UNLOCK(&hints);
tmp = *extcontexts;
- ast_mutex_lock(&conlock);
if (registrar) {
__ast_context_destroy(NULL,registrar);
while (tmp) {
@@ -3549,7 +3564,6 @@ 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
@@ -3557,7 +3571,6 @@ 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_LIST_LOCK(&hints);
AST_LIST_TRAVERSE(&hints, hint, list) {
if (hint->exten == exten)
break;
@@ -3580,10 +3593,12 @@ void ast_merge_contexts_and_delete(struct ast_context **extcontexts, const char
hint->callbacks = this->callbacks;
hint->laststate = this->laststate;
}
- AST_LIST_UNLOCK(&hints);
free(this);
}
+ AST_LIST_UNLOCK(&hints);
+ ast_mutex_unlock(&conlock);
+
return;
}
--
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