linux-kernel - Re: [patch 07/34] alpha: Use generic idle loop

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Date:	Fri, 29 Mar 2013 12:22:54 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
cc:	LKML <linux-kernel@...r.kernel.org>, linux-arch@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Magnus Damm <magnus.damm@...il.com>,
	Richard Henderson <rth@...ddle.net>,
	Ivan Kokshaysky <ink@...assic.park.msu.ru>,
	Matt Turner <mattst88@...il.com>
Subject: Re: [patch 07/34] alpha: Use generic idle loop

On Thu, 28 Mar 2013, Srivatsa S. Bhat wrote:
> (In all my replies, I'm referring to the code in your v2 on your git
> tree, but replying to the corresponding patches in your v1).
> 
> So, in alpha, we poll in cpu idle. In the generic implementation in
> kernel/cpu/idle.c, arch_cpu_idle() is defined as:
> 
> void __weak arch_cpu_idle(void)
> {
>         cpu_idle_poll();
> }
> 
> Should it not have been:
> 
> void __weak arch_cpu_idle(void)
> {
> 	current_set_polling();
>         cpu_idle_poll();
> 	current_clr_polling();
> }
> 
> instead?

Hmm, we should not clear it at all, because we are always polling and
never leave polling mode. So instead of calling cpu_idle_poll from the
weak arch_cpu_idle() we should set cpu_idle_force_poll so we drop into

	if (cpu_idle_force_poll) {
		cpu_idle_poll();
	} else ...

which keeps the polling flag set.

Thanks,

	tglx


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