[Devel] [PATCH 2/3] tty: Avoid threads files iterations in __do_SAK()

[Pavel Tikhomirov]

Please see one comment below, everything else looks good.

> @@ -3029,24 +3030,36 @@ void __do_SAK(struct tty_struct *tty)
>   	/* Now kill any processes that happen to have the
>   	 * tty open.
>   	 */
> -	do_each_thread(g, p) {
> +	for_each_process(p) {
>   		if (p->signal->tty == tty) {
>   			printk(KERN_NOTICE "SAK: killed process %d"
>   			    " (%s): task_session(p)==tty->session\n",
>   			    task_pid_nr(p), p->comm);
> -			send_sig(SIGKILL, p, 1);
> -			continue;
> +			goto kill;
>   		}
> -		task_lock(p);
> -		i = iterate_fd(p->files, 0, this_tty, tty);
> -		if (i != 0) {
> -			printk(KERN_NOTICE "SAK: killed process %d"
> -			    " (%s): fd#%d opened to the tty\n",
> -				    task_pid_nr(p), p->comm, i - 1);
> -			send_sig(SIGKILL, p, 1);
> +
> +		files = NULL;
> +		for_each_thread(p, t) {
> +			if (t->files == files) /* racy but we do not care */
> +				continue;
> +
> +			task_lock(t);
> +			files = t->files;
> +			i = iterate_fd(files, 0, this_tty, tty);
> +			task_unlock(t);
> +
> +			if (i != 0) {
> +				printk(KERN_NOTICE "SAK: killed process %d"
> +					" (%s): fd#%d opened to the tty\n",
> +					task_pid_nr(p), p->comm, i - 1);
> +				goto kill;

We skip all threads which go after "t" if we jump to the label, it seem 
we need a separate "kill" for these loop.

> +			}
>   		}
> -		task_unlock(p);
> -	} while_each_thread(g, p);
> +
> +		continue;
> +kill:
> +		send_sig(SIGKILL, p, 1);
> +	}
>   	qread_unlock(&tasklist_lock);
>   #endif
>   }
> 

-- 
Best regards, Tikhomirov Pavel
Software Developer, Virtuozzo.