Linux中的PCB——tast_struct

PCB的意思是进程控制块，在Linux下的PCB就叫tast_strcut结构体。下面我们就来调研一下这个 tast_strcut里面有什么。
先列出一些总体概括：
1.pid
2.状态：任务状态，退出代码，退出信号等。
3.优先级：相对于其他进程的优先级
4.程序计数器：即将被执行的下一条指令地址
5.内存指针：存放程序代码和数据的指针，还有和其他进程共享内存块的指针。
6.上下文数据：进程执行时处理器的寄存器的数据
7.I/O状态信息：显示的I/O请求，分配给进程的I/O设备
8.记账信息：包括处理器的时间总和，记账号等等。
9.进程地址空间
10.其他信息

下面具体介绍一个重要的内容
一.进程状态（state）

二.进程标识符

三.进程调度信息（优先级）

policy表示进程的调度算法，一般有以下几种：
1.SCHED_NORMAL用于普通进程，通过CFS调度器实现
2.SCHED_BATCH用于非交互的处理器消耗型进程
3.SCHED_IDLE是在系统负载很低时使用
4.SCHED_FIFO（先入先出调度算法）和SCHED_RR（时间片轮转调度算法）都是实时调度策略.

四.进程标记

unsigned int flags; /* per process flags, defined below */ 

它的取值范围如下：

 /** Per process flags*/#define PF_EXITING      0x00000004      /* getting shut down */#define PF_EXITPIDONE   0x00000008      /* pi exit done on shut down */#define PF_VCPU         0x00000010      /* I'm a virtual CPU */#define PF_WQ_WORKER    0x00000020      /* I'm a workqueue worker */#define PF_FORKNOEXEC   0x00000040      /* forked but didn't exec */#define PF_MCE_PROCESS  0x00000080      /* process policy on mce errors */#define PF_SUPERPRIV    0x00000100      /* used super-user privileges */#define PF_DUMPCORE     0x00000200      /* dumped core */#define PF_SIGNALED     0x00000400      /* killed by a signal */#define PF_MEMALLOC     0x00000800      /* Allocating memory */#define PF_NPROC_EXCEEDED 0x00001000    /* set_user noticed that RLIMIT_NPROC was exceeded */#define PF_USED_MATH    0x00002000      /* if unset the fpu must be initialized before use */#define PF_USED_ASYNC   0x00004000      /* used async_schedule*(), used by module init */#define PF_NOFREEZE     0x00008000      /* this thread should not be frozen */#define PF_FROZEN       0x00010000      /* frozen for system suspend */#define PF_FSTRANS      0x00020000      /* inside a filesystem transaction */#define PF_KSWAPD       0x00040000      /* I am kswapd */#define PF_MEMALLOC_NOIO 0x00080000     /* Allocating memory without IO involved */#define PF_LESS_THROTTLE 0x00100000     /* Throttle me less: I clean memory */#define PF_KTHREAD      0x00200000      /* I am a kernel thread */#define PF_RANDOMIZE    0x00400000      /* randomize virtual address space */#define PF_SWAPWRITE    0x00800000      /* Allowed to write to swap */#define PF_NO_SETAFFINITY 0x04000000    /* Userland is not allowed to meddle with cpus_allowed */#define PF_MCE_EARLY    0x08000000      /* Early kill for mce process policy */#define PF_MUTEX_TESTER 0x20000000      /* Thread belongs to the rt mutex tester */#define PF_FREEZER_SKIP 0x40000000      /* Freezer should not count it as freezable */#define PF_SUSPEND_TASK 0x80000000      /* this thread called freeze_processes and should not be frozen */

五.表示进程亲属关系的成员