linux-kernel - Re: [PATCH] powerpc: Make doorbell check preemption safe

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Message-ID: <556FF3F8.1070507@linux.vnet.ibm.com>
Date:	Thu, 04 Jun 2015 12:15:12 +0530
From:	Shreyas B Prabhu <shreyas@...ux.vnet.ibm.com>
To:	Michael Neuling <mikey@...ling.org>
CC:	mpe@...erman.id.au, benh@...nel.crashing.org, paulus@...ba.org,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc: Make doorbell check preemption safe



On Wednesday 20 May 2015 06:30 AM, Michael Neuling wrote:
> On Wed, 2015-05-20 at 00:30 +0530, Shreyas B. Prabhu wrote:
>> Doorbell can be used to cause ipi on cpus which are sibling threads on
>> the same core. So icp_native_cause_ipi checks if the destination cpu
>> is a sibling thread of the current cpu and uses doorbell in such cases.
>>
>> But while running with CONFIG_PREEMPT=y, since this section is
>> preemtible, we can run into issues if after we check if the destination
>> cpu is a sibling cpu, the task gets migrated from a sibling cpu to a
>> cpu on another core.
>>
>> Fix this by using get_cpu()/ put_cpu()
> 
> Thanks.  Looks good and it's boots for me.
> 
> Signed-off-by: Michael Neuling <mikey@...ling.org>
> 
mikey, Thanks!


mpe, if this looks ok, can you please pick it up?

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