linux-kernel - Re: [PREEMPT-RT] [PATCH] s390/cpum_sf: Remove superfluous SMP function call

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Message-ID: <5703A836.7030708@linutronix.de>
Date:	Tue, 5 Apr 2016 13:57:42 +0200
From:	Sebastian Andrzej Siewior <sebastian.siewior@...utronix.de>
To:	rcochran@...utronix.de, Heiko Carstens <heiko.carstens@...ibm.com>
Cc:	Anna-Maria Gleixner <anna-maria@...utronix.de>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
	rt@...utronix.de
Subject: Re: [PREEMPT-RT] [PATCH] s390/cpum_sf: Remove superfluous SMP
 function call

On 04/05/2016 01:51 PM, rcochran@...utronix.de wrote:
> On Tue, Apr 05, 2016 at 01:36:38PM +0200, Heiko Carstens wrote:
>> On Tue, Apr 05, 2016 at 01:23:36PM +0200, Heiko Carstens wrote:
>>> Subsequently, in this case, the setup_pmc_cpu() call will be executed on
>>> the wrong cpu.
>>
>> .. or to illustrate this behaviour: the following patch (white space
>> damaged due to copy-paste) results in the following:
> 
> I guess you are missing the following commit?
…
>     cpu/hotplug: Move online calls to hotplugged cpu

No, Heiko is right here. If one of the "CPU_DOWN_PREPARE" fails then
the following CPU_DOWN_FAILED will be invoked on the correct CPU.

However if we are further down the road and the final ARCH specific
"die" failed (just before CPU_DYING) are invoked then we get this done
on the wrong CPU.

> Thanks,
> Richard

Sebastian