Summary of operating system interview questions (updated from time to time)

1. Talk about threads and processes , The difference between them ？

process ： A process is an independent unit of the system for resource allocation and scheduling , Is the unit of concurrent execution in a system .

Threads ： A thread is an entity of a process , It's also CPU Basic unit of dispatch and dispatch , It's a smaller, independent, basic unit than a process , It is sometimes called lightweight process or lightweight process .

difference ：

（1） A process is the smallest unit of resource allocation , And the thread is CPU Minimum unit of scheduling ;

（2） Create process or undo process , The system has to allocate or recycle resources , The operating system overhead is much greater than the overhead when creating or undoing threads ;

（3） The address spaces of different processes are independent of each other , Threads in the same process share the same address space . The thread of one process is invisible within another process ;

（4） Processes don't interact with each other , A thread that hangs may cause the entire process to hang up ; 

2. The mechanism of thread synchronization ？

Thread synchronization mechanism _ Game cat blog -CSDN Blog _ Synchronization of threads

3. The difference between synchronous and asynchronous ？

Sync ： When a synchronous call is made , The caller has to wait for the result to be returned . Upon receipt of the notice , Then we can carry out the follow-up execution .（ Execute in order ）

asynchronous ： When an asynchronous procedure call is issued , The caller cannot get the return result immediately . The part that actually handles this call is done , Passing state 、 Notifications and callbacks to notify callers .（ Each executive ）

4. The difference between blocking and non blocking ？

The difference between blocking and non blocking - Mai Fei - Blog Garden (cnblogs.com)

5. Four necessary conditions for deadlock in operating system ？