linux-kernel - Re: [PATCH 25/60] microblaze_v4: process and init task function

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Date:	Sat, 28 Jun 2008 13:50:42 +0900
From:	Paul Mundt <lethal@...ux-sh.org>
To:	monstr@...nam.cz
Cc:	linux-kernel@...r.kernel.org, arnd@...db.de,
	linux-arch@...r.kernel.org, stephen.neuendorffer@...inx.com,
	John.Linn@...inx.com, john.williams@...alogix.com, matthew@....cx,
	will.newton@...il.com, drepper@...hat.com,
	microblaze-uclinux@...e.uq.edu.au, grant.likely@...retlab.ca,
	linuxppc-dev@...abs.org, vapier.adi@...il.com,
	alan@...rguk.ukuu.org.uk, hpa@...or.com,
	Michal Simek <monstr@...str.eu>
Subject: Re: [PATCH 25/60] microblaze_v4: process and init task function

On Thu, Jun 26, 2008 at 02:29:54PM +0200, monstr@...nam.cz wrote:
> +void (*pm_power_off)(void) = NULL;
> +EXPORT_SYMBOL(pm_power_off);
> +
> +void cpu_idle(void)
> +{
> +	set_thread_flag(TIF_POLLING_NRFLAG);
> +
> +	while (1) {
> +		while (!need_resched())
> +			cpu_relax();
> +
> +		preempt_enable_no_resched();
> +		schedule();
> +		preempt_disable();
> +	}
> +}
> +
A couple things to note here. You have a pm_power_off, but no pm_idle.

You set TIF_POLLING_NRFLAG but don't have any explicit clearing and
resetting of it if the CPU is sleeping. In the cpu_relax() case this is
ok, but if you have a cpu_sleep() you will want to use in the SMP case,
you will need to handle it explicitly.

Beyond that, you may also want to stub in the
tick_nohz_stop_sched_tick()/tick_nohz_restart_sched_tick() calls, then
when you implement the generic clockevents you will already have the
tickless bits in place.

check_pgt_cache() is also helpful here for quicklist trimming, though you
may not care if you never plan to have an MMU.

You can look at arch/sh/kernel/process_32.c for examples.
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