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obs-scripting: Make callback "removed" variable atomic

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Makes the callback variable "removed" atomic, and on script unload,
first sets all callbacks to removed before actually unloading the script
out of a safety precaution. (See note at the bottom for further details)

This minimizes the possibility of a race condition where the script
callback could be called while those callbacks were being removed.

Big note for this change, this change should eventually be replaced with
a reference counting ownership method where script callbacks can hold a
reference and share ownership of the script if it's still alive while
the script callback is being called. That way the script callbacks can
safely execute. May require a fair amount of reworking of the script
object.
This commit is contained in:
jp9000
2022-03-01 03:04:37 -08:00
parent fbcb053cfa
commit 6d3b1998ef
6 changed files with 71 additions and 29 deletions
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deps/obs-scripting/obs-scripting-python.c
Vendored
+29 -11
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@@ -431,7 +431,7 @@ static void timer_call(struct script_callback *p_cb)
{
struct python_obs_callback *cb = (struct python_obs_callback *)p_cb;
if (p_cb->removed)
if (script_callback_removed(p_cb))
return;
lock_callback(cb);
@@ -476,7 +476,7 @@ static void obs_python_tick_callback(void *priv, float seconds)
{
struct python_obs_callback *cb = priv;
if (cb->base.removed) {
if (script_callback_removed(&cb->base)) {
obs_remove_tick_callback(obs_python_tick_callback, cb);
return;
}
@@ -546,7 +546,7 @@ static void calldata_signal_callback(void *priv, calldata_t *cd)
{
struct python_obs_callback *cb = priv;
if (cb->base.removed) {
if (script_callback_removed(&cb->base)) {
signal_handler_remove_current();
return;
}
@@ -652,7 +652,7 @@ static void calldata_signal_callback_global(void *priv, const char *signal,
{
struct python_obs_callback *cb = priv;
if (cb->base.removed) {
if (script_callback_removed(&cb->base)) {
signal_handler_remove_current();
return;
}
@@ -767,7 +767,7 @@ static void hotkey_pressed(void *p_cb, bool pressed)
{
struct python_obs_callback *cb = p_cb;
if (cb->base.removed)
if (script_callback_removed(&cb->base))
return;
lock_callback(cb);
@@ -803,7 +803,7 @@ static void hotkey_callback(void *p_cb, obs_hotkey_id id, obs_hotkey_t *hotkey,
{
struct python_obs_callback *cb = p_cb;
if (cb->base.removed)
if (script_callback_removed(&cb->base))
return;
if (pressed)
@@ -873,7 +873,7 @@ static bool button_prop_clicked(obs_properties_t *props, obs_property_t *p,
struct python_obs_callback *cb = p_cb;
bool ret = false;
if (cb->base.removed)
if (script_callback_removed(&cb->base))
return false;
lock_callback(cb);
@@ -937,7 +937,7 @@ static bool modified_callback(void *p_cb, obs_properties_t *props,
struct python_obs_callback *cb = p_cb;
bool ret = false;
if (cb->base.removed)
if (script_callback_removed(&cb->base))
return false;
lock_callback(cb);
@@ -1333,6 +1333,24 @@ void obs_python_script_unload(obs_script_t *s)
if (!s->loaded || !python_loaded)
return;
/* ---------------------------- */
/* mark callbacks as removed */
lock_python();
/* XXX: scripts can potentially make callbacks when this happens, so
* this probably still isn't ideal as we can't predict how the
* processor or operating system is going to schedule things. a more
* ideal method would be to reference count the script objects and
* atomically share ownership with callbacks when they're called. */
struct script_callback *cb = data->first_callback;
while (cb) {
os_atomic_set_bool(&cb->removed, true);
cb = cb->next;
}
unlock_python();
/* ---------------------------- */
/* unhook tick function */
@@ -1350,7 +1368,7 @@ void obs_python_script_unload(obs_script_t *s)
data->next_tick = NULL;
}
lock_python();
relock_python();
Py_XDECREF(data->tick);
Py_XDECREF(data->save);
@@ -1364,7 +1382,7 @@ void obs_python_script_unload(obs_script_t *s)
/* ---------------------------- */
/* remove all callbacks */
struct script_callback *cb = data->first_callback;
cb = data->first_callback;
while (cb) {
struct script_callback *next = cb->next;
remove_script_callback(cb);
@@ -1532,7 +1550,7 @@ static void python_tick(void *param, float seconds)
struct python_obs_timer *next = timer->next;
struct python_obs_callback *cb = python_obs_timer_cb(timer);
if (cb->base.removed) {
if (script_callback_removed(&cb->base)) {
python_obs_timer_remove(timer);
} else {
uint64_t elapsed = ts - timer->last_ts;