Process has executed for the maximum allowable time slice
②
I/O interrupt
（
I/O
中断）
③
Memory fault
（内存失效）
Memory address is in virtual memory so it must be brought into main memory
④
Trap
（陷阱）
Error or exception occurred
May cause process to be moved to edit state
⑤
Supervisor call
（系统调用）
Such as file open
3. Illustrated some scenarios where process should blocked?
①
The system fails to apply for resources.
（向系统申请资源时失败）
For example, if A process (A) requests A printer but the printer is in use by another process
(B), process A is blocked.
②
Waiting for an operation.
（等待某种操作）
Process A starts an I/O device. If process A can start an I/O device only after the specified
I/O task is complete, process A automatically blocks after starting the I/O device.
③
New data has not arrived.
（新数据尚未到达）
For cooperative processes, if a process needs to obtain data from another process before it
can process the data, it will enter the blocking state as long as the data has not arrived.
④
Waiting for a new task to arrive.
（等待新任务的到达）
Each time the process completes its task
4. Suppose there are three processes running in an operating system with
multithreading as following:
If the multithreading is supported by user-level implementation（用户级）
and thread T11 is blocked, which thread may be scheduled to run next?
One of T21,T22,T31,T32
If the multithreading is supported by kernel-level implementation（内核级）,
which thread may be scheduled to run next?
One of T12,T21,T22,T31,T32
原因：内核级的实现，
OS
才知道
A
中有
T12
5. What is race condition? Give a program implementation to demonstrate the
mutual exclusion enforced by Test and Set (or exchange) instruction or by
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