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

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Message-ID: <20130826220711.GA21098@madcap2.tricolour.ca>
Date:	Mon, 26 Aug 2013 18:07:11 -0400
From:	Richard Guy Briggs <rgb@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Eric Paris <eparis@...hat.com>, linux-kernel@...r.kernel.org,
	linux-audit@...hat.com, Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>,
	"Serge E. Hallyn" <serge@...lyn.com>
Subject: Re: [PATCH 11/12] pid: rewrite task helper functions avoiding
 task->pid and task->tgid

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@...hat.com>
Senior Software Engineer
Kernel Security
AMER ENG Base Operating Systems
Remote, Ottawa, Canada
Voice: +1.647.777.2635
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