linux-kernel - Re: [git pull] scheduler fix

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Message-ID: <alpine.LFD.2.00.0901071543550.3057@localhost.localdomain>
Date:	Wed, 7 Jan 2009 15:47:52 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ingo Molnar <mingo@...e.hu>
cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [git pull] scheduler fix

On Wed, 7 Jan 2009, Ingo Molnar wrote:
> +		/*
> +		 * Should not call ttwu while holding a rq->lock
> +		 */
> +		spin_unlock(&this_rq->lock);
>  		if (active_balance)
>  			wake_up_process(busiest->migration_thread);
> +		spin_lock(&this_rq->lock);

Btw, this isn't the first time we've wanted to do a wakeup while 
potentially locked.

Is there any way to perhaps go a "wake_up_gentle()" that doesn't need the 
lock, and just basically does a potentially delayed wakeup by just 
scheduling it asynchronously.

That would have solved all those nasty printk issues too. These kinds of 
things don't need the strict "wake up NOW" behaviour - they are more of a 
"kick the dang thing and make sure it wakes up in some timely manner".

		Linus
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