What is the significance of __releases & __acquires in rpm_callback() of power/runtime.c ?

While going thro’ run time power management code in K39 power/runtime.c file, am seeing a function definition as given below. Any idea, what “__releases” & “__acquires” are doing in this function definition?   static int rpm_callback(int (*cb)(struct device *), struct device *dev)                 __releases(&dev->power.lock) __acquires(&dev->power.lock) {                 int retval;                 ….                 return retval; }