linux-kernel - Re: [PATCH] drivers/idle: make intel_idle.c driver more explicitly non-modular

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Message-ID: <20160405043017.GA24357@linutronix.de>
Date:	Tue, 5 Apr 2016 06:30:17 +0200
From:	rcochran@...utronix.de
To:	"Brown, Len" <len.brown@...el.com>
Cc:	"Gortmaker, Paul (Wind River)" <paul.gortmaker@...driver.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Len Brown <lenb@...nel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: Re: [PATCH] drivers/idle: make intel_idle.c driver more explicitly
 non-modular

On Tue, Apr 05, 2016 at 04:20:47AM +0000, Brown, Len wrote:
> The first idle driver to register with cpuidle wins.
> 
> intel_idle should always get the opportunity
> to probe and register before acpi_idle (processor_idle.c)
> 
> When intel_idle was allowed to be modular,
> some distros build their kernel and loaded modules
> such that acpi_idle could probe first.  In such
> a kernel, intel_idle became dead code.
> 
> As intel_idle is a small driver, the q	uick fix
> was to make it Y/N so that it would always probe
> before acpi_idle, no matter how acpi_idle
> is build and loaded.
> 
> Yes, even though intel_idle is a tiny driver, I think
> it would be good to be able to unload it when it doesn't probe.

And that means fixing the race with acpi_idle, right?
 
> Today, it appears that acpi_idle (acpi/processor_idle.c)
> is compiled Y/N.

So it, too, needs work?

> No, I do not believe that cpuidle should bother
> supporting changing idle drivers at run-time.

Huh?  But you just said, "it would be good to be able to unload it
when it doesn't probe."

Thanks,
Richard