From fd3101e8ad320848e966d09f8b64f51628855257 Mon Sep 17 00:00:00 2001
From: Corey Farrell <git@cfware.com>
Date: Tue, 10 Oct 2017 16:09:14 -0400
Subject: [PATCH] astobj2: Run weakproxy callbacks outside of lock.
Copy the list of weakproxy callbacks to temporary memory so they can be
run without holding the weakproxy lock.
Change-Id: Ib167622a8a0f873fd73938f7611b2a5914308047
---
include/asterisk/astobj2.h | 4 ++++
main/astobj2.c | 41 ++++++++++++++++++++------------------
2 files changed, 26 insertions(+), 19 deletions(-)
diff --git a/include/asterisk/astobj2.h b/include/asterisk/astobj2.h
index 484e1e35ca..9b5ec123bc 100644
--- a/include/asterisk/astobj2.h
+++ b/include/asterisk/astobj2.h
@@ -671,6 +671,10 @@ int ao2_weakproxy_subscribe(void *weakproxy, ao2_weakproxy_notification_cb cb, v
* of the cb / data pair. If it was subscribed multiple times it must be
* unsubscribed as many times. The OBJ_MULTIPLE flag can be used to remove
* matching subscriptions.
+ *
+ * \note When it's time to run callbacks they are copied to a temporary list so the
+ * weakproxy can be unlocked before running. That means it's possible for
+ * this function to find nothing before the callback is run in another thread.
*/
int ao2_weakproxy_unsubscribe(void *weakproxy, ao2_weakproxy_notification_cb cb, void *data, int flags);
diff --git a/main/astobj2.c b/main/astobj2.c
index d534900ddf..da2d44e514 100644
--- a/main/astobj2.c
+++ b/main/astobj2.c
@@ -82,8 +82,6 @@ struct ao2_weakproxy_notification {
AST_LIST_ENTRY(ao2_weakproxy_notification) list;
};
-static void weakproxy_run_callbacks(struct ao2_weakproxy *weakproxy);
-
struct ao2_lock_priv {
ast_mutex_t lock;
};
@@ -469,7 +467,7 @@ int __ao2_ref(void *user_data, int delta,
struct astobj2_lockobj *obj_lockobj;
int current_value;
int ret;
- void *weakproxy = NULL;
+ struct ao2_weakproxy *weakproxy = NULL;
if (obj == NULL) {
if (ref_log && user_data) {
@@ -498,6 +496,8 @@ int __ao2_ref(void *user_data, int delta,
#endif
if (weakproxy) {
+ struct ao2_weakproxy cbs;
+
if (current_value == 1) {
/* The only remaining reference is the one owned by the weak object */
struct astobj2 *internal_weakproxy;
@@ -508,8 +508,9 @@ int __ao2_ref(void *user_data, int delta,
internal_weakproxy->priv_data.weakptr = NULL;
obj->priv_data.weakptr = NULL;
- /* Notify the subscribers that weakproxy now points to NULL. */
- weakproxy_run_callbacks(weakproxy);
+ /* transfer list to local copy so callbacks are run with weakproxy unlocked. */
+ cbs.destroyed_cb = weakproxy->destroyed_cb;
+ AST_LIST_HEAD_INIT_NOLOCK(&weakproxy->destroyed_cb);
/* weak is already unlinked from obj so this won't recurse */
ao2_ref(user_data, -1);
@@ -518,6 +519,14 @@ int __ao2_ref(void *user_data, int delta,
ao2_unlock(weakproxy);
if (current_value == 1) {
+ struct ao2_weakproxy_notification *destroyed_cb;
+
+ /* Notify the subscribers that weakproxy now points to NULL. */
+ while ((destroyed_cb = AST_LIST_REMOVE_HEAD(&cbs.destroyed_cb, list))) {
+ destroyed_cb->cb(weakproxy, destroyed_cb->data);
+ ast_free(destroyed_cb);
+ }
+
ao2_ref(weakproxy, -1);
}
}
@@ -796,16 +805,6 @@ void *__ao2_global_obj_ref(struct ao2_global_obj *holder, const char *tag, const
}
-static void weakproxy_run_callbacks(struct ao2_weakproxy *weakproxy)
-{
- struct ao2_weakproxy_notification *destroyed_cb;
-
- while ((destroyed_cb = AST_LIST_REMOVE_HEAD(&weakproxy->destroyed_cb, list))) {
- destroyed_cb->cb(weakproxy, destroyed_cb->data);
- ast_free(destroyed_cb);
- }
-}
-
void *__ao2_weakproxy_alloc(size_t data_size, ao2_destructor_fn destructor_fn,
const char *tag, const char *file, int line, const char *func)
{
@@ -951,6 +950,7 @@ int ao2_weakproxy_subscribe(void *weakproxy, ao2_weakproxy_notification_cb cb, v
{
struct astobj2 *weakproxy_internal = INTERNAL_OBJ_CHECK(weakproxy);
int ret = -1;
+ int hasobj;
if (!weakproxy_internal || weakproxy_internal->priv_data.magic != AO2_WEAK) {
return -1;
@@ -960,7 +960,8 @@ int ao2_weakproxy_subscribe(void *weakproxy, ao2_weakproxy_notification_cb cb, v
ao2_lock(weakproxy);
}
- if (weakproxy_internal->priv_data.weakptr) {
+ hasobj = weakproxy_internal->priv_data.weakptr != NULL;
+ if (hasobj) {
struct ao2_weakproxy *weak = weakproxy;
struct ao2_weakproxy_notification *sub = ast_calloc(1, sizeof(*sub));
@@ -970,15 +971,17 @@ int ao2_weakproxy_subscribe(void *weakproxy, ao2_weakproxy_notification_cb cb, v
AST_LIST_INSERT_HEAD(&weak->destroyed_cb, sub, list);
ret = 0;
}
- } else {
- cb(weakproxy, data);
- ret = 0;
}
if (!(flags & OBJ_NOLOCK)) {
ao2_unlock(weakproxy);
}
+ if (!hasobj) {
+ cb(weakproxy, data);
+ ret = 0;
+ }
+
return ret;
}
--
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