struct task_struct {
  volatile long state;  /* -1 unrunnable, 0 runnable, >0 stopped */
  void *stack;
  atomic_t usage;
  unsigned int flags; /* per process flags, defined below */
  unsigned int ptrace;

  int lock_depth;   /* BKL lock depth */

  int oncpu;

  int prio, static_prio, normal_prio;
  unsigned int rt_priority;
  const struct sched_class *sched_class;
  struct sched_entity se;
  struct sched_rt_entity rt;

  /* list of struct preempt_notifier: */
  struct hlist_head preempt_notifiers;

   * fpu_counter contains the number of consecutive context switches
   * that the FPU is used. If this is over a threshold, the lazy fpu
   * saving becomes unlazy to save the trap. This is an unsigned char
   * so that after 256 times the counter wraps and the behavior turns
   * lazy again; this to deal with bursty apps that only use FPU for
   * a short time
  unsigned char fpu_counter;
  unsigned int btrace_seq;

  unsigned int policy;
  cpumask_t cpus_allowed;

  int rcu_read_lock_nesting;
  char rcu_read_unlock_special;
  struct list_head rcu_node_entry;
#endif /* #ifdef CONFIG_PREEMPT_RCU */
  struct rcu_node *rcu_blocked_node;
#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
  struct rt_mutex *rcu_boost_mutex;
#endif /* #ifdef CONFIG_RCU_BOOST */

  struct sched_info sched_info;

  struct list_head tasks;
  struct plist_node pushable_tasks;

  struct mm_struct *mm, *active_mm;
  struct task_rss_stat  rss_stat;
/* task state */
  int exit_state;
  int exit_code, exit_signal;
  int pdeath_signal;  /*  The signal sent when the parent dies  */
  /* ??? */
  unsigned int personality;
  unsigned did_exec:1;
  unsigned in_execve:1; /* Tell the LSMs that the process is doing an
         * execve */
  unsigned in_iowait:1;

  /* Revert to default priority/policy when forking */
  unsigned sched_reset_on_fork:1;

  pid_t pid;
  pid_t tgid;

  /* Canary value for the -fstack-protector gcc feature */
  unsigned long stack_canary;

   * pointers to (original) parent process, youngest child, younger sibling,
   * older sibling, respectively.  (p->father can be replaced with 
   * p->real_parent->pid)
  struct task_struct *real_parent; /* real parent process */
  struct task_struct *parent; /* recipient of SIGCHLD, wait4() reports */
   * children/sibling forms the list of my natural children
  struct list_head children;  /* list of my children */
  struct list_head sibling; /* linkage in my parent's children list */
  struct task_struct *group_leader; /* threadgroup leader */

   * ptraced is the list of tasks this task is using ptrace on.
   * This includes both natural children and PTRACE_ATTACH targets.
   * p->ptrace_entry is p's link on the p->parent->ptraced list.
  struct list_head ptraced;
  struct list_head ptrace_entry;

  /* PID/PID hash table linkage. */
  struct pid_link pids[PIDTYPE_MAX];
  struct list_head thread_group;

  struct completion *vfork_done;    /* for vfork() */
  int __user *set_child_tid;    /* CLONE_CHILD_SETTID */
  int __user *clear_child_tid;    /* CLONE_CHILD_CLEARTID */

  cputime_t utime, stime, utimescaled, stimescaled;
  cputime_t gtime;
  cputime_t prev_utime, prev_stime;
  unsigned long nvcsw, nivcsw; /* context switch counts */
  struct timespec start_time;     /* monotonic time */
  struct timespec real_start_time;  /* boot based time */
/* mm fault and swap info: this can arguably be seen as either mm-specific or thread-specific */
  unsigned long min_flt, maj_flt;

  struct task_cputime cputime_expires;
  struct list_head cpu_timers[3];

/* process credentials */
  const struct cred __rcu *real_cred; /* objective and real subjective task
           * credentials (COW) */
  const struct cred __rcu *cred;  /* effective (overridable) subjective task
           * credentials (COW) */
  struct cred *replacement_session_keyring; /* for KEYCTL_SESSION_TO_PARENT */

  char comm[TASK_COMM_LEN]; /* executable name excluding path
             - access with [gs]et_task_comm (which lock
               it with task_lock())
             - initialized normally by setup_new_exec */
/* file system info */
  int link_count, total_link_count;
/* ipc stuff */
  struct sysv_sem sysvsem;
/* hung task detection */
  unsigned long last_switch_count;
/* CPU-specific state of this task */
  struct thread_struct thread;
/* filesystem information */
  struct fs_struct *fs;
/* open file information */
  struct files_struct *files;
/* namespaces */
  struct nsproxy *nsproxy;
/* signal handlers */
  struct signal_struct *signal;
  struct sighand_struct *sighand;

  sigset_t blocked, real_blocked;
  sigset_t saved_sigmask; /* restored if set_restore_sigmask() was used */
  struct sigpending pending;

  unsigned long sas_ss_sp;
  size_t sas_ss_size;
  int (*notifier)(void *priv);
  void *notifier_data;
  sigset_t *notifier_mask;
  struct audit_context *audit_context;
  uid_t loginuid;
  unsigned int sessionid;
  seccomp_t seccomp;

/* Thread group tracking */
    u32 parent_exec_id;
    u32 self_exec_id;
/* Protection of (de-)allocation: mm, files, fs, tty, keyrings, mems_allowed,
 * mempolicy */
  spinlock_t alloc_lock;

  /* IRQ handler threads */
  struct irqaction *irqaction;

  /* Protection of the PI data structures: */
  raw_spinlock_t pi_lock;

  /* PI waiters blocked on a rt_mutex held by this task */
  struct plist_head pi_waiters;
  /* Deadlock detection and priority inheritance handling */
  struct rt_mutex_waiter *pi_blocked_on;

  /* mutex deadlock detection */
  struct mutex_waiter *blocked_on;
  unsigned int irq_events;
  unsigned long hardirq_enable_ip;
  unsigned long hardirq_disable_ip;
  unsigned int hardirq_enable_event;
  unsigned int hardirq_disable_event;
  int hardirqs_enabled;
  int hardirq_context;
  unsigned long softirq_disable_ip;
  unsigned long softirq_enable_ip;
  unsigned int softirq_disable_event;
  unsigned int softirq_enable_event;
  int softirqs_enabled;
  int softirq_context;
# define MAX_LOCK_DEPTH 48UL
  u64 curr_chain_key;
  int lockdep_depth;
  unsigned int lockdep_recursion;
  struct held_lock held_locks[MAX_LOCK_DEPTH];
  gfp_t lockdep_reclaim_gfp;

/* journalling filesystem info */
  void *journal_info;

/* stacked block device info */
  struct bio_list *bio_list;

/* VM state */
  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.  */
  struct task_io_accounting ioac;
#if defined(CONFIG_TASK_XACCT)
  u64 acct_rss_mem1;  /* accumulated rss usage */
  u64 acct_vm_mem1; /* accumulated virtual memory usage */
  cputime_t acct_timexpd; /* stime + utime since last update */
  nodemask_t mems_allowed;  /* Protected by alloc_lock */
  int mems_allowed_change_disable;
  int cpuset_mem_spread_rotor;
  int cpuset_slab_spread_rotor;
  /* Control Group info protected by css_set_lock */
  struct css_set __rcu *cgroups;
  /* cg_list protected by css_set_lock and tsk->alloc_lock */
  struct list_head cg_list;
  struct robust_list_head __user *robust_list;

  struct compat_robust_list_head __user *compat_robust_list;
  struct list_head pi_state_list;
  struct futex_pi_state *pi_state_cache;
  struct perf_event_context *perf_event_ctxp[perf_nr_task_contexts];
  struct mutex perf_event_mutex;
  struct list_head perf_event_list;
  struct mempolicy *mempolicy;  /* Protected by alloc_lock */
  short il_next;
  atomic_t fs_excl; /* holding fs exclusive resources */
  struct rcu_head rcu;

   * cache last used pipe for splice
  struct pipe_inode_info *splice_pipe;
  struct task_delay_info *delays;
  int make_it_fail;
  struct prop_local_single dirties;
  int latency_record_count;
  struct latency_record latency_record[LT_SAVECOUNT];
   * time slack values; these are used to round up poll() and
   * select() etc timeout values. These are in nanoseconds.
  unsigned long timer_slack_ns;
  unsigned long default_timer_slack_ns;

  struct list_head  *scm_work_list;
  /* Index of current stored address in ret_stack */
  int curr_ret_stack;
  /* Stack of return addresses for return function tracing */
  struct ftrace_ret_stack *ret_stack;
  /* time stamp for last schedule */
  unsigned long long ftrace_timestamp;
   * Number of functions that haven't been traced
   * because of depth overrun.
  atomic_t trace_overrun;
  /* Pause for the tracing */
  atomic_t tracing_graph_pause;
  /* state flags for use by tracers */
  unsigned long trace;
  /* bitmask of trace recursion */
  unsigned long trace_recursion;
#endif /* CONFIG_TRACING */
#ifdef CONFIG_CGROUP_MEM_RES_CTLR /* memcg uses this to do batch job */
  struct memcg_batch_info {
    int do_batch; /* incremented when batch uncharge started */
    struct mem_cgroup *memcg; /* target memcg of uncharge */
    unsigned long bytes;    /* uncharged usage */
    unsigned long memsw_bytes; /* uncharged mem+swap usage */
  } memcg_batch;