The Story Behind Processes: Mastering the Heart of Linux OS!

// task_struct structure comments://　　==========================long state // Task running state (-1 not runnable, 0 runnable (ready), >0 stopped).long counter // Task running time count (decrementing) (ticks), running time slice.long priority // Running priority. When the task starts running, counter = priority, the larger it is, the longer it runs.long signal // Signal. It is a bitmap, each bit represents a signal, signal value = bit offset + 1.　　struct sigaction sigaction[32] // Signal execution attribute structure, corresponding to the operation and flag information to be executed for the signal.　　long blocked // Process signal mask (corresponding to signal bitmap).//　　--------------------------　　int exit_code // Exit code when the task execution stops, which will be taken by its parent process.　　unsigned long start_code // Code segment address.　　unsigned long end_code // Code length (in bytes).　　unsigned long end_data // Code length + data length (in bytes).　　unsigned long brk // Total length (in bytes).　　unsigned long start_stack // Stack segment address.　　long pid // Process identifier (process number).　　long father // Parent process number.　　long pgrp // Parent process group number.　　long session // Session number.　　long leader // Session leader.　　unsigned short uid // User identifier (user id).　　unsigned short euid // Effective user id.　　unsigned short suid // Saved user id.　　unsigned short gid // Group identifier (group id).　　unsigned short egid // Effective group id.　　unsigned short sgid // Saved group id.　　long alarm // Alarm timer value (ticks).　　long utime // User mode running time (ticks).　　long stime // System mode running time (ticks).　　long cutime // Child process user mode running time.　　long cstime // Child process system mode running time.　　long start_time // The moment the process starts running.　　unsigned short used_math // Flag: whether a coprocessor has been used.//　　--------------------------　　int tty // The sub-device number of the tty used by the process. -1 means not used.　　unsigned short umask // File creation attribute mask bit.　　struct m_inode * pwd // Current working directory inode structure.　　struct m_inode * root // Root directory inode structure.　　struct m_inode * executable // Executable file inode structure.　　unsigned long close_on_exec // Bitmap flag for closing file handles on execution. (See include/fcntl.h)　　struct file * filp[NR_OPEN] // File table structure used by the process.//　　--------------------------struct desc_struct ldt[3] // Local descriptor table for this task. 0-empty, 1-code segment cs, 2-data and stack segment ds&ss.

    Identifier: Unique identifier describing this process, used to distinguish it from other processes.        State: Task state, exit code, exit signal, etc.        Priority: Priority relative to other processes.        Program counter: Address of the next instruction to be executed in the program.        Memory pointer: Includes pointers to program code and process-related data, as well as pointers to shared memory blocks with other processes.Context data: Data in the processor registers during process execution [Example of rest study, add image CPU, registers].I/O status information: Includes displayed I/O requests, I/O devices allocated to the process, and the list of files used by the process.Accounting information: May include total processor time, total clock counts used, time limits, accounting numbers, and other information.