Improved sensor thread-safety
This fixes an issue where the main thread would hang indefinitely when polling events if sensors were initialized and shutdown on another thread.
This commit is contained in:
Sam Lantinga
parent
4ee0e5a984
commit
6b93e788fa
4 changed files with 204 additions and 112 deletions
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@ -49,18 +49,79 @@ static SDL_SensorDriver *SDL_sensor_drivers[] = {
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&SDL_DUMMY_SensorDriver
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#endif
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};
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static SDL_Mutex *SDL_sensor_lock = NULL; /* This needs to support recursive locks */
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#ifndef SDL_THREAD_SAFETY_ANALYSIS
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static
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#endif
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SDL_Mutex *SDL_sensor_lock = NULL; /* This needs to support recursive locks */
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static SDL_AtomicInt SDL_sensor_lock_pending;
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static int SDL_sensors_locked;
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static SDL_bool SDL_sensors_initialized;
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static SDL_Sensor *SDL_sensors SDL_GUARDED_BY(SDL_sensor_lock) = NULL;
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static SDL_AtomicInt SDL_last_sensor_instance_id SDL_GUARDED_BY(SDL_sensor_lock);
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char SDL_sensor_magic;
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void SDL_LockSensors(void) SDL_ACQUIRE(SDL_sensor_lock)
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#define CHECK_SENSOR_MAGIC(sensor, retval) \
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if (!sensor || sensor->magic != &SDL_sensor_magic) { \
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SDL_InvalidParamError("sensor"); \
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SDL_UnlockSensors(); \
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return retval; \
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}
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SDL_bool SDL_SensorsInitialized(void)
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{
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SDL_LockMutex(SDL_sensor_lock);
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return SDL_sensors_initialized;
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}
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void SDL_UnlockSensors(void) SDL_RELEASE(SDL_sensor_lock)
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void SDL_LockSensors(void)
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{
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SDL_UnlockMutex(SDL_sensor_lock);
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(void)SDL_AtomicIncRef(&SDL_sensor_lock_pending);
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SDL_LockMutex(SDL_sensor_lock);
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(void)SDL_AtomicDecRef(&SDL_sensor_lock_pending);
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++SDL_sensors_locked;
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}
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void SDL_UnlockSensors(void)
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{
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SDL_bool last_unlock = SDL_FALSE;
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--SDL_sensors_locked;
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if (!SDL_sensors_initialized) {
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/* NOTE: There's a small window here where another thread could lock the mutex after we've checked for pending locks */
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if (!SDL_sensors_locked && SDL_AtomicGet(&SDL_sensor_lock_pending) == 0) {
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last_unlock = SDL_TRUE;
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}
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}
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/* The last unlock after sensors are uninitialized will cleanup the mutex,
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* allowing applications to lock sensors while reinitializing the system.
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*/
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if (last_unlock) {
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SDL_Mutex *sensor_lock = SDL_sensor_lock;
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SDL_LockMutex(sensor_lock);
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{
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SDL_UnlockMutex(SDL_sensor_lock);
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SDL_sensor_lock = NULL;
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}
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SDL_UnlockMutex(sensor_lock);
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SDL_DestroyMutex(sensor_lock);
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} else {
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SDL_UnlockMutex(SDL_sensor_lock);
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}
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}
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SDL_bool SDL_SensorsLocked(void)
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{
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return (SDL_sensors_locked > 0) ? SDL_TRUE : SDL_FALSE;
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}
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void SDL_AssertSensorsLocked(void)
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{
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SDL_assert(SDL_SensorsLocked());
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}
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int SDL_InitSensors(void)
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@ -78,12 +139,23 @@ int SDL_InitSensors(void)
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}
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#endif /* !SDL_EVENTS_DISABLED */
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SDL_LockSensors();
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SDL_sensors_initialized = SDL_TRUE;
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status = -1;
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for (i = 0; i < SDL_arraysize(SDL_sensor_drivers); ++i) {
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if (SDL_sensor_drivers[i]->Init() >= 0) {
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status = 0;
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}
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}
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SDL_UnlockSensors();
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if (status < 0) {
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SDL_QuitSensors();
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}
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return status;
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}
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@ -320,33 +392,22 @@ SDL_Sensor *SDL_GetSensorFromInstanceID(SDL_SensorID instance_id)
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return sensor;
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}
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/*
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* Checks to make sure the sensor is valid.
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*/
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static int SDL_IsSensorValid(SDL_Sensor *sensor)
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{
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int valid;
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if (sensor == NULL) {
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SDL_SetError("Sensor hasn't been opened yet");
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valid = 0;
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} else {
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valid = 1;
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}
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return valid;
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}
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/*
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* Get the friendly name of this sensor
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*/
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const char *SDL_GetSensorName(SDL_Sensor *sensor)
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{
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if (!SDL_IsSensorValid(sensor)) {
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return NULL;
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}
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const char *retval;
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return sensor->name;
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SDL_LockSensors();
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{
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CHECK_SENSOR_MAGIC(sensor, NULL);
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retval = sensor->name;
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}
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SDL_UnlockSensors();
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return retval;
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}
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/*
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@ -354,11 +415,17 @@ const char *SDL_GetSensorName(SDL_Sensor *sensor)
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*/
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SDL_SensorType SDL_GetSensorType(SDL_Sensor *sensor)
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{
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if (!SDL_IsSensorValid(sensor)) {
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return SDL_SENSOR_INVALID;
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}
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SDL_SensorType retval;
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return sensor->type;
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SDL_LockSensors();
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{
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CHECK_SENSOR_MAGIC(sensor, SDL_SENSOR_INVALID);
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retval = sensor->type;
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}
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SDL_UnlockSensors();
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return retval;
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}
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/*
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@ -366,11 +433,17 @@ SDL_SensorType SDL_GetSensorType(SDL_Sensor *sensor)
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*/
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int SDL_GetSensorNonPortableType(SDL_Sensor *sensor)
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{
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if (!SDL_IsSensorValid(sensor)) {
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return -1;
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}
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int retval;
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return sensor->non_portable_type;
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SDL_LockSensors();
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{
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CHECK_SENSOR_MAGIC(sensor, -1);
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retval = sensor->non_portable_type;
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}
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SDL_UnlockSensors();
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return retval;
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}
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/*
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@ -378,11 +451,17 @@ int SDL_GetSensorNonPortableType(SDL_Sensor *sensor)
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*/
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SDL_SensorID SDL_GetSensorInstanceID(SDL_Sensor *sensor)
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{
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if (!SDL_IsSensorValid(sensor)) {
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return 0;
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}
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SDL_SensorID retval;
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return sensor->instance_id;
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SDL_LockSensors();
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{
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CHECK_SENSOR_MAGIC(sensor, 0);
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retval = sensor->instance_id;
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}
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SDL_UnlockSensors();
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return retval;
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}
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/*
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@ -390,12 +469,15 @@ SDL_SensorID SDL_GetSensorInstanceID(SDL_Sensor *sensor)
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*/
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int SDL_GetSensorData(SDL_Sensor *sensor, float *data, int num_values)
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{
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if (!SDL_IsSensorValid(sensor)) {
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return -1;
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}
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SDL_LockSensors();
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{
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CHECK_SENSOR_MAGIC(sensor, -1);
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num_values = SDL_min(num_values, SDL_arraysize(sensor->data));
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SDL_memcpy(data, sensor->data, num_values * sizeof(*data));
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}
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SDL_UnlockSensors();
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num_values = SDL_min(num_values, SDL_arraysize(sensor->data));
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SDL_memcpy(data, sensor->data, num_values * sizeof(*data));
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return 0;
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}
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@ -407,42 +489,39 @@ void SDL_CloseSensor(SDL_Sensor *sensor)
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SDL_Sensor *sensorlist;
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SDL_Sensor *sensorlistprev;
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if (!SDL_IsSensorValid(sensor)) {
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return;
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}
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SDL_LockSensors();
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{
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CHECK_SENSOR_MAGIC(sensor,);
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/* First decrement ref count */
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if (--sensor->ref_count > 0) {
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SDL_UnlockSensors();
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return;
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}
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sensor->driver->Close(sensor);
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sensor->hwdata = NULL;
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sensorlist = SDL_sensors;
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sensorlistprev = NULL;
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while (sensorlist) {
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if (sensor == sensorlist) {
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if (sensorlistprev) {
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/* unlink this entry */
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sensorlistprev->next = sensorlist->next;
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} else {
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SDL_sensors = sensor->next;
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}
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break;
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/* First decrement ref count */
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if (--sensor->ref_count > 0) {
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SDL_UnlockSensors();
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return;
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}
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sensorlistprev = sensorlist;
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sensorlist = sensorlist->next;
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sensor->driver->Close(sensor);
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sensor->hwdata = NULL;
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sensorlist = SDL_sensors;
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sensorlistprev = NULL;
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while (sensorlist) {
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if (sensor == sensorlist) {
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if (sensorlistprev) {
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/* unlink this entry */
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sensorlistprev->next = sensorlist->next;
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} else {
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SDL_sensors = sensor->next;
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}
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break;
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}
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sensorlistprev = sensorlist;
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sensorlist = sensorlist->next;
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}
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/* Free the data associated with this sensor */
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SDL_free(sensor->name);
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SDL_free(sensor);
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}
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SDL_free(sensor->name);
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/* Free the data associated with this sensor */
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SDL_free(sensor);
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SDL_UnlockSensors();
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}
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@ -463,16 +542,13 @@ void SDL_QuitSensors(void)
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SDL_sensor_drivers[i]->Quit();
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}
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SDL_UnlockSensors();
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#ifndef SDL_EVENTS_DISABLED
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SDL_QuitSubSystem(SDL_INIT_EVENTS);
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#endif
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if (SDL_sensor_lock) {
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SDL_DestroyMutex(SDL_sensor_lock);
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SDL_sensor_lock = NULL;
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}
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SDL_sensors_initialized = SDL_FALSE;
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SDL_UnlockSensors();
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}
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/* These are global for SDL_syssensor.c and SDL_events.c */
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@ -481,6 +557,8 @@ int SDL_SendSensorUpdate(Uint64 timestamp, SDL_Sensor *sensor, Uint64 sensor_tim
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{
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int posted;
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SDL_AssertSensorsLocked();
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/* Allow duplicate events, for things like steps and heartbeats */
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/* Update internal sensor state */
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@ -510,7 +588,13 @@ int SDL_SendSensorUpdate(Uint64 timestamp, SDL_Sensor *sensor, Uint64 sensor_tim
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void SDL_UpdateSensor(SDL_Sensor *sensor)
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{
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sensor->driver->Update(sensor);
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SDL_LockSensors();
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{
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CHECK_SENSOR_MAGIC(sensor,);
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sensor->driver->Update(sensor);
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}
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SDL_UnlockSensors();
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}
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void SDL_UpdateSensors(void)
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