linux-kernel - Re: [PATCH 16/18] 2.6.40: x86 idle APM: remove deprecated apm_cpu

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Message-id: <alpine.LFD.2.02.1104021529580.18682@x980>
Date:	Sat, 02 Apr 2011 15:44:30 -0400 (EDT)
From:	Len Brown <lenb@...nel.org>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	Len Brown <len.brown@...el.com>
Subject: Re: [PATCH 16/18] 2.6.40: x86 idle APM: remove deprecated
 apm_cpu_idle()

> > There is some doubt whether the APM idle feature
> > to call into the BIOS from the idle loop is reliable.
> > Certainly it was known to fail on some machines,
> 
> And it was known to work on lots - a point that despite repeated
> reminding you seem keen to ignore.
> 
> The fundamental problem I have with this patch set is this
> 
> You've provided no architectural overall justification for all this
> effort. What is the big picture around your crusade here ? What is the
> grand plan ?

This patch series was posted in reply to a table of contents

https://lkml.org/lkml/2011/4/2/8

"By the end of this series, pm_idle is removed as a public
 x86 idle-loop registration mechanism.  A few other things are
 cleaned up in the process."

I labeled it "idle cleanup - v3" -- I'm sorry if it went un-noticed
because I neglected to put the [PATCH 0/18] on it.

Trinabh also replied to you, pointing one of the previous
LKML discussions about the mis-use of pm_idle.

> > but more importantly, APM machines have not shipped
> > for a decade and so finding machines to test the code
> > is problematic.
> 
> So don't test it - if it's wrong someone will let you know, believe me 8)
> 
> And 2.6.40 is far too soon - it takes about a year for stuff to rattle
> through to leading edge distro users in bulk

If you insist.

We'll create a new APM cpuidle driver in Linux (Trinabh prototyped one),
and at the same time, schedule it for removal in a year.  Personally,
I think it is make-work, and in real-life it is more likely to do
more harm than removing apm_idle, but I don't want to stand in the
way of process.

thanks,
-Len

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