カーネルとスタックとプロセス

struct task_struct {
 #...
 /* -1 unrunnable, 0 runnable, >0 stopped: */
 volatile long state;

 /*
  * This begins the randomizable portion of task_struct. Only
  * scheduling-critical items should be added above here.
  */
 randomized_struct_fields_start

 void *stack;
 atomic_t usage;
 /* Per task flags (PF_*), defined further below: */
 unsigned int flags;
 unsigned int ptrace;

 #...

 int on_rq;

 int prio;
 int static_prio;
 int normal_prio;
 unsigned int rt_priority;

 const struct sched_class *sched_class;
 struct sched_entity se;
 struct sched_rt_entity rt;
 #...
 struct sched_dl_entity dl;

 #...

 /*
  * Pointers to the (original) parent process, youngest child, younger sibling,
  * older sibling, respectively.  (p->father can be replaced with
  * p->real_parent->pid)
  */

 /* Real parent process: */
 struct task_struct __rcu *real_parent;

 /* Recipient of SIGCHLD, wait4() reports: */
 struct task_struct __rcu *parent;

 /*
  * Children/sibling form the list of natural children:
  */
 struct list_head children;
 struct list_head sibling;
 struct task_struct *group_leader;

 /*
  * 'ptraced' is the list of tasks this task is using ptrace() on.
  *
  * This includes both natural children and PTRACE_ATTACH targets.
  * 'ptrace_entry' is this task'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 list_head thread_node;

 struct completion *vfork_done;

 /* CLONE_CHILD_SETTID: */
 int __user *set_child_tid;

 /* CLONE_CHILD_CLEARTID: */
 int __user *clear_child_tid;

 u64 utime;
 u64 stime;

 #...
}

                          <=　(プリエンプション/タイムクォンタムを使い切る)
プロセス作成 --> [アイドル状態] => [実行可能] => [処理中] => [ゾンビ状態]
                      ^                      |
                      |------[スリープ]<-------|  (I/O など: ブロック)