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Subject: Re: [RFC PATCH 0/2] x86: Fix missing core serialization on migration
To: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
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From: Daniel Bristot de Oliveira <bristot@redhat.com>
Message-ID: <95f902ea-3e97-0280-2d52-28cadef7806d@redhat.com>
Date: Tue, 14 Nov 2017 19:24:22 +0100
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On 11/14/2017 07:17 PM, Peter Zijlstra wrote:
> On Tue, Nov 14, 2017 at 07:01:55PM +0100, Daniel Bristot de Oliveira wrote:
>> On 11/14/2017 06:40 PM, Peter Zijlstra wrote:
>>> On Tue, Nov 14, 2017 at 06:17:13PM +0100, Daniel Bristot de Oliveira wrote:
>>>
>>>> IIRC, if the dest cpu is idle and the system is with idle=poll, no IPI
>>>> is fired as well, but that is not a very common case.
>>>
>>> You're thinking about wake from idle? That is almost always without IPI,
>>> even without idle=poll.
>>>
>>
>> I meant the resched_curr(rq) of an rq on another CPU. If the dest is
>> idle && idle=poll, the IPI will not be send.
> 
> I'm saying the IPI will not be send even without idle=poll. MWAIT based
> idle will also have TIF_POLLING_NRFLAG set.
> 

Yeah! you are right! I missed that point... sorry :-)

-- Daniel