Re: [PATCH] exec: Cleanup exec from a non thread group leader.

[Oleg Nesterov <oleg@tv-sign.ru>]

Eric W. Biederman wrote:
>
> And for good measure we set the thread group leaders
> exit_signal to -1 so it will self reap.  We are actually
> past the point where that matters but it can't hurt, and
> it might help someday.
> ...
>               leader->exit_state = EXIT_DEAD;
> +             leader->exit_signal = -1;

I disagree. The leader is already practically reaped, it is EXIT_DEAD.
I think this change will confuse the reader who will try to understand
why do we need this subtle assignment.

>  void switch_exec_pids(task_t *leader, task_t *thread)
>  {
> -	__detach_pid(leader, PIDTYPE_PID);
> -	__detach_pid(leader, PIDTYPE_TGID);
> -	__detach_pid(leader, PIDTYPE_PGID);
> -	__detach_pid(leader, PIDTYPE_SID);
> -
> -	__detach_pid(thread, PIDTYPE_PID);
> -	__detach_pid(thread, PIDTYPE_TGID);
> -
> -	leader->pid = leader->tgid = thread->pid;
> -	thread->pid = thread->tgid;
> -
> -	attach_pid(thread, PIDTYPE_PID, thread->pid);
> -	attach_pid(thread, PIDTYPE_TGID, thread->tgid);
> +	detach_pid(thread, PIDTYPE_PID);
> +	thread->pid = leader->pid;
> +	attach_pid(thread, PIDTYPE_PID,  thread->pid);
>  	attach_pid(thread, PIDTYPE_PGID, thread->signal->pgrp);
> -	attach_pid(thread, PIDTYPE_SID, thread->signal->session);
> -	list_add_tail(&thread->tasks, &init_task.tasks);

The last deletion is wrong, I beleive.

> +	attach_pid(thread, PIDTYPE_SID,  thread->signal->session);
>  
> -	attach_pid(leader, PIDTYPE_PID, leader->pid);
> -	attach_pid(leader, PIDTYPE_TGID, leader->tgid);
> -	attach_pid(leader, PIDTYPE_PGID, leader->signal->pgrp);
> -	attach_pid(leader, PIDTYPE_SID, leader->signal->session);
> +	detach_pid(leader, PIDTYPE_PID);
> +	detach_pid(leader, PIDTYPE_TGID);
> +	detach_pid(leader, PIDTYPE_PGID);
> +	detach_pid(leader, PIDTYPE_SID);
>  }

I think most of detach_pid()s could be replaced with __detach_pid(),
this will save unneccesary pid_hash scanning

Oleg.
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