[Linux]进程（十二）--task_struct结构体

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struct task_struct {
    volatile long state; /* -1 不可运行, 0 可运行, >0 表示停止 */
    void *stack;
    atomic_t usage;
    unsigned long flags; /* 每进程标志 */
    unsigned long ptrace;
    int lock_depth; /* 大内核锁深度 */
    int prio, static_prio, normal_prio;
    struct list_head run_list;
    const struct sched_class *sched_class;
    struct sched_entity se;
    unsigned short ioprio;
    unsigned long policy;
    cpumask_t cpus_allowed;
    unsigned int time_slice;
#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
    struct sched_info sched_info;
#endif
    struct list_head tasks;
    /*
    * ptrace_list/ptrace_children forms the list of my children
    * that were stolen by a ptracer.
    */
    struct list_head ptrace_children;
    struct list_head ptrace_list;
    struct mm_struct *mm, *active_mm;
/* 进程状态 */
    struct linux_binfmt *binfmt;
    long exit_state;
    int exit_code, exit_signal;
    int pdeath_signal; /* 在父进程终止的时候发送的信号 */
    unsigned int personality;
    unsigned did_exec:1;
    pid_t pid;
    pid_t tgid;
    struct task_struct *real_parent; /* 真正的父进程（被调试的情况下） */
    struct task_struct *parent; /* 父进程 ，parent和real_parent的区别：real_parent是亲爹，调fork的那个，parent呢是干爹，大部分情况下亲爹干爹是一个人，ps看到的是干爹，什么时候亲爹干爹不一样的，比如有一种情况，比如亲爹死了，但是呢又得有一个父进程，比如1号进程就会被当成父进程。但进程不是1号fork出来的。*/
    struct list_head children; /* 子进程链表 */
    struct list_head sibling; /* 连接到父进程的子进程的链表 */
    struct task_struct *group_leader; /* 线程组组长 */
    /* PID与PID散列表的联系*/
    struct pid_link pids[PIDTYPE_MAX];
    struct list_head thread_group;
    struct completion *vfork_done; /* 用于vfork() */
    int __user *set_child_tid; /* CLONE_CHILD_SETTID */
    int __user *clear_child_tid; /* CLONE_CHILD_CLEARTID */
    unsigned long rt_priority;
    cputime_t utime, stime, utimescaled, stimescaled;;
    unsigned long nvcsw, nivcsw; /* 上下文切换计数 */
    struct timespec start_time; /* 单调时间 */
    struct timespec real_start_time; /* 启动以来的时间 */
    unsigned long min_flt, maj_flt;
    cputime_t it_prof_expires, it_virt_expires;
    unsigned long long it_sched_expires;
    struct list_head cpu_timers[3];
/* 进程身份凭据 */
    uid_t uid,euid,suid,fsuid;
    gid_t gid,egid,sgid,fsgid;
    struct group_info *group_info;
    kernel_cap_t cap_effective, cap_inheritable, cap_permitted;
    unsigned keep_capabilities:1;
    struct user_struct *user;
    char comm[TASK_COMM_LEN]; /* 去除路径后的可执行文件名称*/
/* 文件系统信息 */
    int link_count, total_link_count;
/* ipc stuff */
    struct sysv_sem sysvsem;
/* 当前进程特定的cpu信息 */
    struct thread_struct thread;
/* filesystem information */
    struct fs_struct *fs;
/* open file information */
    struct files_struct *files;
/* namespace */
    struct nsproxy *nsproxy;
/* signal handlers */
    struct signal_struct *signal;
    struct sighand_struct *sighand;
    sigset_t blocked, real_blocked;
    sigset_t saved_sigmask; /* To be restored with TIF_RESTORE_SIGMASK */
    struct sigpending pending;
    unsigned long sas_ss_sp;
    size_t sas_ss_size;
    int (*notifier)(void *priv);
    void *notifier_data;
    sigset_t *notifier_mask;
#ifdef CONFIG_SECURITY
v   oid *security;
#endif
/* 线程组跟踪 */
    u32 parent_exec_id;
    u32 self_exec_id;
/* 日志文件系统信息 */
    void *journal_info;
/* 虚拟内存状态 */
    struct reclaim_state *reclaim_state;
    struct backing_dev_info *backing_dev_info;
    struct io_context *io_context;
    unsigned long ptrace_message;
    siginfo_t *last_siginfo; /* For ptrace use. */
...
};

atomic_t usage; 有几个进程正在使用此结构