Re: [PATCH] sched: clarify ptrace's effect on task_struct->parent

[Oleg Nesterov <oleg@redhat.com>]

On 09/10, Ziran Zhang wrote:
> The current comment for the parent field does not explain that it can be
> temporarily replaced by the tracer when the task is being ptraced.
> 
> This can lead to confusion, so clarify the comment to document this
> important behavior.
> 
> No functional change.
> 
> Signed-off-by: Ziran Zhang <zhangcoder@yeah.net>
> ---
>  include/linux/sched.h | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 705970d07..977859a63 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1093,7 +1093,11 @@ struct task_struct {
>  	/* Real parent process: */
>  	struct task_struct __rcu	*real_parent;
>  
> -	/* Recipient of SIGCHLD, wait4() reports: */
> +	/*
> +	 * Recipient of SIGCHLD, wait4() reports. Normally the same as
> +	 * real_parent, but temporarily replaced by the tracer while the
> +	 * task is ptraced.
> +	 */
>  	struct task_struct __rcu	*parent;

Well. Not sure this comment needs to be updated...

Anyway, this looks like overdocumentation to me. Perhaps just

	/* Recipient of SIGCHLD, wait4() reports: ->real_parent or ptracer */

?

Oleg.