linux-kernel - Re: [PATCH] don't use task->pid/tgid in same_thread_group/has_group_leader

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Date:	Wed, 29 May 2013 13:54:45 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.cz>,
	Sergey Dyasly <dserrg@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] don't use task->pid/tgid in same_thread_group/has_group_leader_pid

Oleg Nesterov <oleg@...hat.com> writes:

> task_struct->pid/tgid should go away.
>
> 1. Change same_thread_group() to use task->signal for comparison.
>
> 2. Change has_group_leader_pid(task) to compare task_pid(task) with
>    signal->leader_pid.

Reviewed-by: "Eric W. Biederman" <ebiederm@...ssion.com>

This change looks good, thanks.

The posix cpu timers usage of has_group_leader_pid looks a little iffy,
but this change doesn't look like it will break them.

Thanks for this cleanup Oleg.

> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> ---
>  include/linux/sched.h |    8 ++++----
>  1 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 178a8d9..ce51dfd 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -2179,15 +2179,15 @@ static inline bool thread_group_leader(struct task_struct *p)
>   * 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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