linux-kernel - Re: [PATCH] Revert "cpuidle: Make drivers initialize polling state"

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Message-ID: <20180206163134.GO5453@intel.com>
Date:   Tue, 6 Feb 2018 18:31:34 +0200
From:   Ville Syrjälä <ville.syrjala@...ux.intel.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Sudeep Holla <sudeep.holla@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [PATCH] Revert "cpuidle: Make drivers initialize polling state"

On Mon, Feb 05, 2018 at 06:56:31PM +0100, Rafael J. Wysocki wrote:
> On Monday, February 5, 2018 3:04:45 PM CET Ville Syrjälä wrote:
> > On Sun, Feb 04, 2018 at 10:18:07AM +0100, Rafael J. Wysocki wrote:
> > > On Sun, Feb 4, 2018 at 10:12 AM, Rafael J. Wysocki <rafael@...nel.org> wrote:
> > > > On Mon, Jan 22, 2018 at 5:27 PM, Ville Syrjala
> > > > <ville.syrjala@...ux.intel.com> wrote:
> > > >> From: Ville Syrjälä <ville.syrjala@...ux.intel.com>
> > > >>
> > > >> This reverts commit 1b39e3f813b4685c7a30ae964d5529a1b0e3a286.
> > > >>
> > > >> Makes my P3 machine oops somewhere in cpuidle. I suspect
> > > >> CONFIG_ACPI=n may have something to do with this.
> > > >
> > > > And if you don't do CONFIG_ACPI=n, does it still oops?
> > 
> > Don't think I actually tried that. I can give it a whirl tonight.
> > 
> > I think this machine should actually have ACPI, but it inherited
> > the .config from a P2 machine that did not. Apparently I was too
> > lazy to change .config when I swapped in the "new" machine.
> 
> I guess it would work, but never mind.
> 
> > > >
> > > > Anyway, there are later changes depending on this one, so reverting it
> > > > won't work in general.
> > > >
> > > > Let me look deeper at this.
> > > 
> > > What's there in /sys/devices/system/cpu/cpuidle/current_driver on your
> > > system with the problematic commit reverted?
> > 
> > # cat /sys/devices/system/cpu/cpuidle/current_driver
> > apm_idle
> 
> That is the key bit: I overlooked this little fellow.
> 
> Does the below (untested here) help?
> 
> ---
>  arch/x86/kernel/apm_32.c |    1 +
>  1 file changed, 1 insertion(+)
> 
> Index: linux-pm/arch/x86/kernel/apm_32.c
> ===================================================================
> --- linux-pm.orig/arch/x86/kernel/apm_32.c
> +++ linux-pm/arch/x86/kernel/apm_32.c
> @@ -2389,6 +2389,7 @@ static int __init apm_init(void)
>  	if (HZ != 100)
>  		idle_period = (idle_period * HZ) / 100;
>  	if (idle_threshold < 100) {
> +		cpuidle_poll_state_init(&apm_idle_driver);
>  		if (!cpuidle_register_driver(&apm_idle_driver))
>  			if (cpuidle_register_device(&apm_cpuidle_device))
>  				cpuidle_unregister_driver(&apm_idle_driver);

Yep, this works. Thanks.

Tested-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>

-- 
Ville Syrjälä
Intel OTC