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

[Richard Guy Briggs]

On Thu, Aug 22, 2013 at 09:08:48PM +0200, Oleg Nesterov wrote:
> On 08/20, Richard Guy Briggs wrote:
> >
> >  static inline int is_global_init(struct task_struct *tsk)
> >  {
> > -	return tsk->pid == 1;
> > +	return task_pid_nr(tsk) == 1;
> >  }
> 
> Probably it would be better to simply kill it. Almost every usage is
> wrong.

Can you be more clear?  I don't follow.  It should instead return a
boolean.  Usage of is_global_init() or task_pid_nr()?

If is_global_init(), is that because they could be unaware of pid
namespaces?

If task_pid_nr(), is that for the same reason?

> >  static inline bool is_idle_task(const struct task_struct *p)
> >  {
> > -	return p->pid == 0;
> > +	return task_pid(p) == &init_struct_pid;
> >  }
> 
> hmm. there should be a simpler check for this...

Other than the original, this one is pretty simple.  What did you have
in mind?

> >  static inline int has_group_leader_pid(struct task_struct *p)
> >  {
> > -	return p->pid == p->tgid;
> > +	return task_pid(p) == task_tgid(p);
> >  }
> >  
> >  static inline
> >  int same_thread_group(struct task_struct *p1, struct task_struct *p2)
> >  {
> > -	return p1->tgid == p2->tgid;
> > +	return task_tgid(p1) == task_tgid(p2);
> 
> This is suboptinal. See the attached
> include-linux-schedh-dont-use-task-pid-tgid-in-same_thread_group-has_group_leader_pid.patch
> from -mm below.

I'm fine with that if it is deemed better.  The point was to remove the
dependence on task_struct::tgid.

> Oleg.

- RGB

--
Richard Guy Briggs <rbriggs at redhat.com>
Senior Software Engineer
Kernel Security
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