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Reduce the chance of destroying the joystick mutex while it's in use 

Fixes https://github.com/libsdl-org/SDL/issues/7811
main
Sam Lantinga 2023-06-12 15:26:34 -07:00
parent 6ab846b688
commit cdc40ee054
1 changed files with 17 additions and 4 deletions
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21
src/joystick/SDL_joystick.c
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@ -109,6 +109,7 @@ static SDL_JoystickDriver *SDL_joystick_drivers[] = {
static
#endif
SDL_Mutex *SDL_joystick_lock = NULL; /* This needs to support recursive locks */
static SDL_AtomicInt SDL_joystick_lock_pending;
static int SDL_joysticks_locked;
static SDL_bool SDL_joysticks_initialized;
static SDL_bool SDL_joysticks_quitting = SDL_FALSE;
@ -138,23 +139,35 @@ SDL_bool SDL_JoysticksQuitting(void)
void SDL_LockJoysticks(void)
{
SDL_AtomicIncRef(&SDL_joystick_lock_pending);
SDL_LockMutex(SDL_joystick_lock);
SDL_AtomicDecRef(&SDL_joystick_lock_pending);
++SDL_joysticks_locked;
}
void SDL_UnlockJoysticks(void)
{
SDL_Mutex *joystick_lock = SDL_joystick_lock;
SDL_bool last_unlock = SDL_FALSE;
--SDL_joysticks_locked;
SDL_UnlockMutex(SDL_joystick_lock);
if (!SDL_joysticks_initialized) {
if (!SDL_joysticks_locked && SDL_AtomicGet(&SDL_joystick_lock_pending) == 0) {
/* NOTE: There's a small window here where another thread could lock the mutex */
SDL_joystick_lock = NULL;
last_unlock = SDL_TRUE;
}
}
SDL_UnlockMutex(joystick_lock);
/* The last unlock after joysticks are uninitialized will cleanup the mutex,
* allowing applications to lock joysticks while reinitializing the system.
*/
if (SDL_joystick_lock && !SDL_joysticks_locked && !SDL_joysticks_initialized) {
SDL_DestroyMutex(SDL_joystick_lock);
SDL_joystick_lock = NULL;
if (last_unlock) {
SDL_DestroyMutex(joystick_lock);
}
}