●●● ●●●● 4.4 Threading Issues ●●●●● ●●●● ●●●0● ●●●0 o The difficulty with cancellation occurs in situations (1)Resources have been allocated to a canceled thread (2)a thread is canceled while in the midst of updating data which is sharing with other threads o This becomes es pecially troublesome with asynchronous cancellation o Deferred cancellation can be executed at cancellation points when it can be canceled safel25 4.4 Threading Issues ⚫ The difficulty with cancellation occurs in situations （1）Resources have been allocated to a canceled thread （2）A thread is canceled while in the midst of updating data which is sharing with other threads ⚫ This becomes especially troublesome with asynchronous cancellation ⚫ Deferred cancellation can be executed at cancellation points when it can be canceled safely