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Revamped joystick locking

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This makes the joystick locking more robust by holding the lock while updating joysticks.

The lock should be held when calling any SDL joystick function on a different thread than the one calling SDL_PumpEvents() and SDL_JoystickUpdate().

It is now possible to hold the lock while reinitializing the joystick subsystem, however any open joysticks will become invalid and potentially cause crashes if used afterwards.

Fixes https://github.com/libsdl-org/SDL/issues/6063
This commit is contained in:
Sam Lantinga
2022-08-30 11:42:13 -07:00
parent ff233fe306
commit 40bd4feedc
5 changed files with 138 additions and 115 deletions
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218
src/joystick/SDL_joystick.c
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@@ -106,13 +106,21 @@ static SDL_JoystickDriver *SDL_joystick_drivers[] = {
&SDL_DUMMY_JoystickDriver
#endif
};
static SDL_bool SDL_joystick_allows_background_events = SDL_FALSE;
static SDL_bool SDL_joysticks_initialized;
static SDL_bool SDL_joysticks_quitting = SDL_FALSE;
static SDL_Joystick *SDL_joysticks = NULL;
static SDL_bool SDL_updating_joystick = SDL_FALSE;
static SDL_mutex *SDL_joystick_lock = NULL; /* This needs to support recursive locks */
static int SDL_joysticks_locked;
static SDL_atomic_t SDL_next_joystick_instance_id;
static int SDL_joystick_player_count = 0;
static SDL_JoystickID *SDL_joystick_players = NULL;
static SDL_bool SDL_joystick_allows_background_events = SDL_FALSE;
SDL_bool
SDL_JoysticksInitialized(void)
{
return SDL_joysticks_initialized;
}
void
SDL_LockJoysticks(void)
@@ -120,21 +128,76 @@ SDL_LockJoysticks(void)
if (SDL_joystick_lock) {
SDL_LockMutex(SDL_joystick_lock);
}
++SDL_joysticks_locked;
}
void
SDL_UnlockJoysticks(void)
{
--SDL_joysticks_locked;
if (SDL_joystick_lock) {
SDL_UnlockMutex(SDL_joystick_lock);
/* The last unlock after joysticks are uninitialized will cleanup the mutex,
* allowing applications to lock joysticks while reinitializing the system.
*/
if (!SDL_joysticks_locked &&
!SDL_joysticks_initialized) {
SDL_DestroyMutex(SDL_joystick_lock);
SDL_joystick_lock = NULL;
}
}
}
static void
SDL_AssertJoysticksLocked(void)
{
SDL_assert(SDL_joysticks_locked > 0);
}
SDL_bool
SDL_JoysticksQuitting(void)
{
return SDL_joysticks_quitting;
}
/*
* Get the driver and device index for an API device index
* This should be called while the joystick lock is held, to prevent another thread from updating the list
*/
static SDL_bool
SDL_GetDriverAndJoystickIndex(int device_index, SDL_JoystickDriver **driver, int *driver_index)
{
int i, num_joysticks, total_joysticks = 0;
SDL_AssertJoysticksLocked();
if (device_index >= 0) {
for (i = 0; i < SDL_arraysize(SDL_joystick_drivers); ++i) {
num_joysticks = SDL_joystick_drivers[i]->GetCount();
if (device_index < num_joysticks) {
*driver = SDL_joystick_drivers[i];
*driver_index = device_index;
return SDL_TRUE;
}
device_index -= num_joysticks;
total_joysticks += num_joysticks;
}
}
SDL_SetError("There are %d joysticks available", total_joysticks);
return SDL_FALSE;
}
static int
SDL_FindFreePlayerIndex()
{
int player_index;
SDL_AssertJoysticksLocked();
for (player_index = 0; player_index < SDL_joystick_player_count; ++player_index) {
if (SDL_joystick_players[player_index] == -1) {
return player_index;
@@ -148,6 +211,8 @@ SDL_GetPlayerIndexForJoystickID(SDL_JoystickID instance_id)
{
int player_index;
SDL_AssertJoysticksLocked();
for (player_index = 0; player_index < SDL_joystick_player_count; ++player_index) {
if (instance_id == SDL_joystick_players[player_index]) {
break;
@@ -162,6 +227,8 @@ SDL_GetPlayerIndexForJoystickID(SDL_JoystickID instance_id)
static SDL_JoystickID
SDL_GetJoystickIDForPlayerIndex(int player_index)
{
SDL_AssertJoysticksLocked();
if (player_index < 0 || player_index >= SDL_joystick_player_count) {
return -1;
}
@@ -176,6 +243,8 @@ SDL_SetJoystickIDForPlayerIndex(int player_index, SDL_JoystickID instance_id)
int device_index;
int existing_player_index;
SDL_AssertJoysticksLocked();
if (player_index >= SDL_joystick_player_count) {
SDL_JoystickID *new_players = (SDL_JoystickID *)SDL_realloc(SDL_joystick_players, (player_index + 1)*sizeof(*SDL_joystick_players));
if (!new_players) {
@@ -229,29 +298,39 @@ SDL_JoystickInit(void)
{
int i, status;
SDL_GameControllerInitMappings();
/* Create the joystick list lock */
if (!SDL_joystick_lock) {
SDL_joystick_lock = SDL_CreateMutex();
}
/* See if we should allow joystick events while in the background */
SDL_AddHintCallback(SDL_HINT_JOYSTICK_ALLOW_BACKGROUND_EVENTS,
SDL_JoystickAllowBackgroundEventsChanged, NULL);
#if !SDL_EVENTS_DISABLED
if (SDL_InitSubSystem(SDL_INIT_EVENTS) < 0) {
return -1;
}
#endif /* !SDL_EVENTS_DISABLED */
SDL_LockJoysticks();
SDL_joysticks_initialized = SDL_TRUE;
SDL_GameControllerInitMappings();
/* See if we should allow joystick events while in the background */
SDL_AddHintCallback(SDL_HINT_JOYSTICK_ALLOW_BACKGROUND_EVENTS,
SDL_JoystickAllowBackgroundEventsChanged, NULL);
status = -1;
for (i = 0; i < SDL_arraysize(SDL_joystick_drivers); ++i) {
if (SDL_joystick_drivers[i]->Init() >= 0) {
status = 0;
}
}
SDL_UnlockJoysticks();
if (status < 0) {
SDL_JoystickQuit();
}
return status;
}
@@ -279,32 +358,6 @@ SDL_JoystickID SDL_GetNextJoystickInstanceID()
return SDL_AtomicIncRef(&SDL_next_joystick_instance_id);
}
/*
* Get the driver and device index for an API device index
* This should be called while the joystick lock is held, to prevent another thread from updating the list
*/
SDL_bool
SDL_GetDriverAndJoystickIndex(int device_index, SDL_JoystickDriver **driver, int *driver_index)
{
int i, num_joysticks, total_joysticks = 0;
if (device_index >= 0) {
for (i = 0; i < SDL_arraysize(SDL_joystick_drivers); ++i) {
num_joysticks = SDL_joystick_drivers[i]->GetCount();
if (device_index < num_joysticks) {
*driver = SDL_joystick_drivers[i];
*driver_index = device_index;
return SDL_TRUE;
}
device_index -= num_joysticks;
total_joysticks += num_joysticks;
}
}
SDL_SetError("There are %d joysticks available", total_joysticks);
return SDL_FALSE;
}
/*
* Get the implementation dependent name of a joystick
*/
@@ -1138,11 +1191,6 @@ SDL_JoystickClose(SDL_Joystick *joystick)
return;
}
if (SDL_updating_joystick) {
SDL_UnlockJoysticks();
return;
}
if (joystick->rumble_expiration) {
SDL_JoystickRumble(joystick, 0, 0, 0);
}
@@ -1194,13 +1242,9 @@ SDL_JoystickQuit(void)
{
int i;
/* Make sure we're not getting called in the middle of updating joysticks */
SDL_LockJoysticks();
while (SDL_updating_joystick) {
SDL_UnlockJoysticks();
SDL_Delay(1);
SDL_LockJoysticks();
}
SDL_joysticks_quitting = SDL_TRUE;
/* Stop the event polling */
while (SDL_joysticks) {
@@ -1218,7 +1262,6 @@ SDL_JoystickQuit(void)
SDL_joystick_players = NULL;
SDL_joystick_player_count = 0;
}
SDL_UnlockJoysticks();
#if !SDL_EVENTS_DISABLED
SDL_QuitSubSystem(SDL_INIT_EVENTS);
@@ -1227,13 +1270,12 @@ SDL_JoystickQuit(void)
SDL_DelHintCallback(SDL_HINT_JOYSTICK_ALLOW_BACKGROUND_EVENTS,
SDL_JoystickAllowBackgroundEventsChanged, NULL);
if (SDL_joystick_lock) {
SDL_mutex *mutex = SDL_joystick_lock;
SDL_joystick_lock = NULL;
SDL_DestroyMutex(mutex);
}
SDL_GameControllerQuitMappings();
SDL_joysticks_quitting = SDL_FALSE;
SDL_joysticks_initialized = SDL_FALSE;
SDL_UnlockJoysticks();
}
@@ -1301,7 +1343,12 @@ void SDL_PrivateJoystickAdded(SDL_JoystickID device_instance)
return;
}
SDL_LockJoysticks();
SDL_AssertJoysticksLocked();
if (SDL_JoysticksQuitting()) {
return;
}
if (SDL_GetDriverAndJoystickIndex(device_index, &driver, &driver_device_index)) {
player_index = driver->GetDevicePlayerIndex(driver_device_index);
}
@@ -1311,7 +1358,6 @@ void SDL_PrivateJoystickAdded(SDL_JoystickID device_instance)
if (player_index >= 0) {
SDL_SetJoystickIDForPlayerIndex(player_index, device_instance);
}
SDL_UnlockJoysticks();
#if !SDL_EVENTS_DISABLED
{
@@ -1425,6 +1471,8 @@ void SDL_PrivateJoystickRemoved(SDL_JoystickID device_instance)
SDL_Event event;
#endif
SDL_AssertJoysticksLocked();
/* Find this joystick... */
device_index = 0;
for (joystick = SDL_joysticks; joystick; joystick = joystick->next) {
@@ -1450,12 +1498,10 @@ void SDL_PrivateJoystickRemoved(SDL_JoystickID device_instance)
UpdateEventsForDeviceRemoval(device_index, SDL_CONTROLLERDEVICEADDED);
#endif /* !SDL_EVENTS_DISABLED */
SDL_LockJoysticks();
player_index = SDL_GetPlayerIndexForJoystickID(device_instance);
if (player_index >= 0) {
SDL_joystick_players[player_index] = -1;
}
SDL_UnlockJoysticks();
}
int
@@ -1464,6 +1510,8 @@ SDL_PrivateJoystickAxis(SDL_Joystick *joystick, Uint8 axis, Sint16 value)
int posted;
SDL_JoystickAxisInfo *info;
SDL_AssertJoysticksLocked();
/* Make sure we're not getting garbage or duplicate events */
if (axis >= joystick->naxes) {
return 0;
@@ -1527,6 +1575,8 @@ SDL_PrivateJoystickHat(SDL_Joystick *joystick, Uint8 hat, Uint8 value)
{
int posted;
SDL_AssertJoysticksLocked();
/* Make sure we're not getting garbage or duplicate events */
if (hat >= joystick->nhats) {
return 0;
@@ -1568,6 +1618,8 @@ SDL_PrivateJoystickBall(SDL_Joystick *joystick, Uint8 ball,
{
int posted;
SDL_AssertJoysticksLocked();
/* Make sure we're not getting garbage events */
if (ball >= joystick->nballs) {
return 0;
@@ -1618,6 +1670,8 @@ SDL_PrivateJoystickButton(SDL_Joystick *joystick, Uint8 button, Uint8 state)
}
#endif /* !SDL_EVENTS_DISABLED */
SDL_AssertJoysticksLocked();
/* Make sure we're not getting garbage or duplicate events */
if (button >= joystick->nbuttons) {
return 0;
@@ -1654,7 +1708,7 @@ void
SDL_JoystickUpdate(void)
{
int i;
SDL_Joystick *joystick, *next;
SDL_Joystick *joystick;
if (!SDL_WasInit(SDL_INIT_JOYSTICK)) {
return;
@@ -1662,17 +1716,6 @@ SDL_JoystickUpdate(void)
SDL_LockJoysticks();
if (SDL_updating_joystick) {
/* The joysticks are already being updated */
SDL_UnlockJoysticks();
return;
}
SDL_updating_joystick = SDL_TRUE;
/* Make sure the list is unlocked while dispatching events to prevent application deadlocks */
SDL_UnlockJoysticks();
#ifdef SDL_JOYSTICK_HIDAPI
/* Special function for HIDAPI devices, as a single device can provide multiple SDL_Joysticks */
HIDAPI_UpdateDevices();
@@ -1680,11 +1723,6 @@ SDL_JoystickUpdate(void)
for (joystick = SDL_joysticks; joystick; joystick = joystick->next) {
if (joystick->attached) {
/* This driver should always be != NULL, but seeing a crash in the wild...? */
if (!joystick->driver) {
continue; /* nothing we can do, and other things use joystick->driver below here. */
}
joystick->driver->Update(joystick);
if (joystick->delayed_guide_button) {
@@ -1692,36 +1730,14 @@ SDL_JoystickUpdate(void)
}
}
if (joystick->rumble_expiration) {
SDL_LockJoysticks();
/* Double check now that the lock is held */
if (joystick->rumble_expiration &&
SDL_TICKS_PASSED(SDL_GetTicks(), joystick->rumble_expiration)) {
SDL_JoystickRumble(joystick, 0, 0, 0);
}
SDL_UnlockJoysticks();
if (joystick->rumble_expiration &&
SDL_TICKS_PASSED(SDL_GetTicks(), joystick->rumble_expiration)) {
SDL_JoystickRumble(joystick, 0, 0, 0);
}
if (joystick->trigger_rumble_expiration) {
SDL_LockJoysticks();
/* Double check now that the lock is held */
if (joystick->trigger_rumble_expiration &&
SDL_TICKS_PASSED(SDL_GetTicks(), joystick->trigger_rumble_expiration)) {
SDL_JoystickRumbleTriggers(joystick, 0, 0, 0);
}
SDL_UnlockJoysticks();
}
}
SDL_LockJoysticks();
SDL_updating_joystick = SDL_FALSE;
/* If any joysticks were closed while updating, free them here */
for (joystick = SDL_joysticks; joystick; joystick = next) {
next = joystick->next;
if (joystick->ref_count <= 0) {
SDL_JoystickClose(joystick);
if (joystick->trigger_rumble_expiration &&
SDL_TICKS_PASSED(SDL_GetTicks(), joystick->trigger_rumble_expiration)) {
SDL_JoystickRumbleTriggers(joystick, 0, 0, 0);
}
}