linux-kernel - Re: [RFC,PATCH 5/5] exec: RT sub-thread can livelock and monopolize CPU on exec

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Date:	Sun, 19 Aug 2007 12:38:27 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Roland McGrath <roland@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Gautham R Shenoy <ego@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC,PATCH 5/5] exec: RT sub-thread can livelock and monopolize CPU on exec

On 08/18, Roland McGrath wrote:
>
> Maybe it can use wait_task_inactive, which IIUC is being changed to address
> the same RT issue.

The group_leader can sleep before it enters exit_notify(). In that case
wait_task_inactive() returns, and we still need some polling to wait for
EXIT_ZOMBIE.

> OTOH, notify_count exists only for this.  So maybe the
> better way is to clean that whole mechanism up somehow.

Yes sure. But in any case I think we should avoid polling, we need some
notification from exit_notify().

> The exit.c changes
> in your patch seem to be making it more mysterious rather than less so.

I completely agree.

Oleg.

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