[PATCH 11/12] pid: rewrite task helper functions avoiding task->pid and task->tgid

[Peter Zijlstra]

On Mon, Dec 16, 2013 at 05:20:51PM -0500, Richard Guy Briggs wrote:

 >  static inline bool is_idle_task(const struct task_struct *p)
 >  {
 > -	return p->pid == 0;
 > +	return task_pid(p) == &init_struct_pid;
 >  }

> I'll stick with task_pid_nr(p) == 0.

We're going to probably switch to:

  return p->flags & PF_IDLE;

Soon, because people are playing silly tricks and want normal threads
to temporarily appear to be the idle thread (idle time injection).