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

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Date:	Thu, 22 Aug 2013 21:08:48 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Richard Guy Briggs <rgb@...hat.com>
Cc:	linux-audit@...hat.com, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	Eric Paris <eparis@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	John Johansen <john.johansen@...onical.com>,
	James Morris <james.l.morris@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kentaro Takeda <takedakn@...data.co.jp>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>
Subject: Re: [PATCH 11/12] pid: rewrite task helper functions avoiding
	task->pid and task->tgid

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.

>  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...

>  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.

Oleg.


--- a/include/linux/sched.h~include-linux-schedh-dont-use-task-pid-tgid-in-same_thread_group-has_group_leader_pid
+++ a/include/linux/sched.h
@@ -2179,15 +2179,15 @@ static inline bool thread_group_leader(s
  * all we care about is that we have a task with the appropriate
  * pid, we don't actually care if we have the right task.
  */
-static inline int has_group_leader_pid(struct task_struct *p)
+static inline bool has_group_leader_pid(struct task_struct *p)
 {
-	return p->pid == p->tgid;
+	return task_pid(p) == p->signal->leader_pid;
 }
 
 static inline
-int same_thread_group(struct task_struct *p1, struct task_struct *p2)
+bool same_thread_group(struct task_struct *p1, struct task_struct *p2)
 {
-	return p1->tgid == p2->tgid;
+	return p1->signal == p2->signal;
 }
 
 static inline struct task_struct *next_thread(const struct task_struct *p)

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