linux-kernel - Re: preempt_check

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Message-ID: <alpine.DEB.2.02.1403062146060.18573@ionos.tec.linutronix.de>
Date:	Thu, 6 Mar 2014 21:52:42 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Ville Syrjälä <ville.syrjala@...ux.intel.com>
cc:	linux-kernel@...r.kernel.org, peterz@...radead.org,
	mingo@...nel.org
Subject: Re: preempt_check_resched() gone?

On Thu, 6 Mar 2014, Ville Syrjälä wrote:
> Hi,
> 
> It appears preempt_check_resched() is no longer available for modules
> since [1]. So now I'm left wondering what is one supposed to use after
> local_irq_enable(). Documentation/preempt-locking.txt still says one
> should do a check, but the tool to do that was taken away.

The documentation is slightly misleading. The point is:

If you have an irq disabled section and you do a wakeup inside this
section which causes the need resched bit to be set, then
local_irq_enable/restore wont do an preemption check.

If you merily poke at a few device registers then nothing will set
need resched and you're good.

Thanks,

	tglx