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

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Message-ID: <52DAD2B1.2050401@zytor.com>
Date:	Sat, 18 Jan 2014 11:14:57 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Mike Galbraith <bitbucket@...ine.de>,
	Peter Zijlstra <peterz@...radead.org>
CC:	Stephen Rothwell <sfr@...b.auug.org.au>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, Len Brown <lenb@...nel.org>,
	linux-next@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: linux-next: build failure after merge of the tip tree

On 01/18/2014 07:21 AM, Mike Galbraith wrote:
> On Sat, 2014-01-18 at 13:44 +0100, Peter Zijlstra wrote: 
>> On Sat, Jan 18, 2014 at 10:46:06AM +0100, Mike Galbraith wrote:
>>>
>>> I hope it doesn't look quite like that, next-20140117 is -ENOBOOT on
>>> Q6600 box.  See below for an alternative.
>>
>> Urgh, I see, we call the idle arch_cpu_idle() callback with irqs
>> disabled.
>>
>> Could something like this work?
>>
>> 	local_irq_enable();
>> 	mwait_idle_with_hints(0,0);
>>
>> The interrupt enable window is slightly larger, but I'm not immediately
>> seeing a problem with that.
> 
> Yup, works just fine.  Less is more.
> 
> Nice to see a _progression_ in the pipe too btw.
> 

This means an interrupt window is open and we can take an interrupt
between checking need_resched and the MWAIT, which couldn't happen with
__sti_mwait().

Are we sure that is actually safe?

	-hpa


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