linux-kernel - Re: 2.6.21-rc6-mm1

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Date:	Tue, 10 Apr 2007 22:20:07 -0700
From:	Stephane Eranian <eranian@....hp.com>
To:	Venki Pallipadi <venkatesh.pallipadi@...el.com>
Cc:	Adam Belay <abelay@...ell.com>, Andi Kleen <ak@...e.de>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, randy.dunlap@...cle.com,
	lenb@...nel.org
Subject: Re: 2.6.21-rc6-mm1

Venki,

On Tue, Apr 10, 2007 at 05:15:14PM -0700, Venki Pallipadi wrote:
> > > x86-64 expects all idle handlers to enable interrupts before returning from
> > > idle handler. This is due to enter_idle(), exit_idle() races. Make
> > > cpuidle_idle_call() confirm to this when there is no pm_idle_old.
> > > 
> > > Also, cpuidle look at the return values of attch_driver() and set
> > > current_driver to NULL if attach fails on all CPUs.
> > 
> > My vote would be to instead remove enter_idle() and exit_idle() from
> > x86-64, just as was done with i386.  Performance monitoring
> > infrastructure shouldn't be interfering with the idle interrupt
> > delivery, as that could only hurt performance...  Besides, there's
> > probably a better way of doing this than an idle notifier anyway.
> > 
> 
> Agreed. I did not like local_irq_enable() in cpuidle either, but added it
> anyway as it was a corner case when cpuidle is active and no driver is
> active and not a common case. I thought we will have it as a bandaid solution
> until enter_idle, exit_idle is around.
> 
> Andi/Stephane: What are the plans around enter_idle exit_idle in x86-64.
> Is it still being used by perfmon for x86-64 arch?
> 
The next kernel patch for Perfmon will not make use of the idle notification
anymore on any platform.

-- 
-Stephane
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