linux-kernel - Re: [PATCH RFC] x86: avoid atomic operation in test_and_set_bit

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Message-ID: <20110326095709.GB8706@elte.hu>
Date:	Sat, 26 Mar 2011 10:57:09 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andi Kleen <andi@...stfloor.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jack Steiner <steiner@....com>,
	Jan Beulich <JBeulich@...ell.com>,
	Borislav Petkov <bp@...64.org>,
	Nick Piggin <npiggin@...nel.dk>,
	"x86@...nel.org" <x86@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>, tee@....com,
	Nikanth Karthikesan <knikanth@...e.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH RFC] x86: avoid atomic operation in test_and_set_bit_lock
 if possible


* Eric Dumazet <eric.dumazet@...il.com> wrote:

> > > > By doing the above the BIOS should release the performance counter, and 
> > > > the kernel's "perf" should not encounter a conflict.
> > > > 
> > > > The document that you are looking for is here: (please see page 8 and 
> > > > later): 
> > > > http://h20000.www2.hp.com/bc/docs/support/SupportManual/c01804533/c01804533.pdf
> 
> Thanks Peter !
> 
> I was not aware of the hidden "CTRL-A" feature on RBSU, so I never met these 
> configuration settings ("Service Options" added in main menu)
> 
> I already was in "Power regulator mode : Static High mode" QPI Link power 
> management : Disabled
> 
> I have latest released I24 BIOS
> DMI: HP ProLiant BL460c G6, BIOS I24 01/29/2011
> 
> 1) I disabled "Power and Utilization Monitoring" _and_ "Memory
> Pre-Failure Notification"
> 
> Still I got the 'MSR 38d is 330' error
> 
> 2) I then disabled Intel Turbo boost
> 
> Same error
> 
> 3) Minimum Processor idle Power state
>   From C1E-State --> No C-states
> 
> Same error
> 
> Tricky isnt it ?

This kind of user-configurability reminds me of Mr. Prosser from the local 
council who wants to knock down Arthur Dent’s house with a bulldozer to make 
way for a new bypass:

 "But the plans were on display ..."

 "On display? I eventually had to go down to the cellar to find them."

 "That's the display department."

 "With a flashlight."

 "Ah, well the lights had probably gone."

 "So had the stairs."

 "But look, you found the notice didn't you?"

 "Yes," said Arthur, "yes I did. It was on display in the bottom of a locked 
  filing cabinet stuck in a disused lavatory with a sign on the door saying 
  'Beware of the Leopard'."

	Ingo
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