linux-kernel - Re: linux-next: build failure after merge of the tip tree

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Message-ID: <52DCF832.9050704@zytor.com>
Date:	Mon, 20 Jan 2014 02:19:30 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Peter Zijlstra <peterz@...radead.org>, Len Brown <lenb@...nel.org>
CC:	Stephen Rothwell <sfr@...b.auug.org.au>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, linux-next@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: linux-next: build failure after merge of the tip tree

On 01/20/2014 02:13 AM, Peter Zijlstra wrote:
> On Mon, Jan 20, 2014 at 09:30:21AM +0100, Peter Zijlstra wrote:
>> Then make them so. The fact was that most of the mwait idle sites
>> were bloody broken. And the single mwait_idle_with_hints() function
>> presents a single nice function that does all the required magics.
> 
> To stress this a bit more; have a look see at mwwait_idle_with_hints();
> it does a whole lot of subtle magic.
> 
>  - current_{set,clr}_polling*(), these are crucial in not missing and
>    wrecking NEED_RESCHED state.
> 
>  - X86_FEATURE_CLFLUSH_MONTIOR quirk
> 
>  - Does the monitor(); if (!need_resched()) mwait() thing.
> 
> All of those are required for a correct and functional idle loop. And
> I've seen sites where any or all of the above were missing/broken.
> 
> Not unifying the lot into a simple usable function is just stupid --
> history has shown people simply cannot be trusted to get this right.
> 

I don't think anyone is arguing that.  The question is rather if the
implementation is correct, and if it is ready for the merge window.

	-hpa

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