linux-kernel - Re: [PATCH [RT] 11/14] optimize the !printk fastpath through the lock acquisition

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Message-ID: <9810cff90802221643g7d993af4k33f29fb4a4663407@mail.gmail.com>
Date:	Fri, 22 Feb 2008 16:43:40 -0800
From:	"Bill Huey (hui)" <bill.huey@...il.com>
To:	gregory.haskins@...il.com
Cc:	"Pavel Machek" <pavel@....cz>,
	"Gregory Haskins" <ghaskins@...ell.com>, mingo@...e.hu,
	a.p.zijlstra@...llo.nl, tglx@...utronix.de, rostedt@...dmis.org,
	linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	kevin@...man.org, cminyard@...sta.com, dsingleton@...sta.com,
	dwalker@...sta.com, npiggin@...e.de, dsaxena@...xity.net,
	ak@...e.de, gregkh@...e.de, sdietrich@...ell.com,
	pmorreale@...ell.com, mkohari@...ell.com
Subject: Re: [PATCH [RT] 11/14] optimize the !printk fastpath through the lock acquisition

On Fri, Feb 22, 2008 at 2:20 PM, Gregory Haskins
<gregory.haskins.ml@...il.com> wrote:
>  Agreed, but it's still correct afaict.  I added an extra might_sleep()
>  to a path that really might sleep.  I should have mentioned that in the
>  header.
>
>  In any case, its moot.  Andi indicated this patch is probably a no-op so
>  I was considering dropping it on the v2 pass.

The might_sleep is annotation and well as a conditional preemption
point for the regular kernel. You might want to do a schedule check
there, but it's the wrong function if memory serves me correctly. It's
reserved for things that actually are design to sleep. The rt_spin*()
function are really a method of preserving BKL semantics across real
schedule() calls. You'd have to use something else instead for that
purpose like cond_reschedule() instead.

bill
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