linux-kernel - Re: [PATCH 1/1] hung_task: Change hung_task.c to use for_each_process

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Date:	Tue, 17 Mar 2015 18:09:20 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Aaron Tomlin <atomlin@...hat.com>
Cc:	akpm@...ux-foundation.org, rientjes@...gle.com,
	dwysocha@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] hung_task: Change hung_task.c to use
	for_each_process_thread()

On 03/17, Aaron Tomlin wrote:
>
> --- a/kernel/hung_task.c
> +++ b/kernel/hung_task.c
> @@ -169,7 +169,7 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
>  		return;
>  
>  	rcu_read_lock();
> -	do_each_thread(g, t) {
> +	for_each_process_thread(g, t) {
>  		if (!max_count--)
>  			goto unlock;
>  		if (!--batch_count) {
> @@ -180,7 +180,7 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
>  		/* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */
>  		if (t->state == TASK_UNINTERRUPTIBLE)
>  			check_hung_task(t, timeout);
> -	} while_each_thread(g, t);
> +	}


Acked-by: Oleg Nesterov <oleg@...hat.com>



Perhaps it also makes sense to improve this rcu_lock_break a bit...
For example, if 't' is dead but 'g' is alive we can continue the
"for_each_process" part of this double loop. And if 't' is still
alive then we can find the new leader and continue...

But I agree, lets start from this fix, then we will see.

Oleg.

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