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From: Shreyas B Prabhu <shreyas@linux.vnet.ibm.com>
To: Preeti U Murthy <preeti@linux.vnet.ibm.com>,
	linux-kernel@vger.kernel.org,
	Michael Ellerman <mpe@ellerman.id.au>,
	"benh@kernel.crashing.org" <benh@kernel.crashing.org>
Cc: linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v4 3/3] powerpc/powernv: Introduce sysfs control for fastsleep workaround behavior
Date: Wed, 15 Apr 2015 11:35:53 +0530	[thread overview]
Message-ID: <552DFFC1.6050806@linux.vnet.ibm.com> (raw)
In-Reply-To: <552CCF5E.5040201@linux.vnet.ibm.com>


> 
> A point that bothers me here is if we can potentially race with cpu
> hotplug ? If cpuX and its siblings are offline and it was interrupted to
> come online:
> 
> cpuX                                     cpuY
> Interrupted to come online
> Undo workaround
> 
>                                 Nop the fastsleep_workaround_exit path
>                                 IPI online cores: apply workaround once
> 
> Set yourself in the online mask
>                                 Nop the fastsleep_workaround_entry path
> 
> 
> This results in cpuX undoing the workaround on its core, never to set it
> back again.
> 
> So should we protect the region between the beginning and end of
> patching instructions with get_online_cpus() and put_online_cpus() ?
> 

Nice catch. I had missed this. Sending out a patch correcting this.

Thanks,
Shreyas

      reply	other threads:[~2015-04-15  6:06 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-14  1:56 [PATCH v4 0/3] powerpc: powernv: Fastsleep workaround behavior Shreyas B. Prabhu
2015-04-14  1:56 ` [PATCH v4 1/3] powerpc: Fix cpu_online_cores_map to return only online threads mask Shreyas B. Prabhu
2015-04-14  1:56 ` [PATCH v4 2/3] powerpc/powernv: Move cpuidle related code from setup.c to new file Shreyas B. Prabhu
2015-04-14  5:07   ` Preeti U Murthy
2015-04-14  1:56 ` [PATCH v4 3/3] powerpc/powernv: Introduce sysfs control for fastsleep workaround behavior Shreyas B. Prabhu
2015-04-14  5:59   ` Preeti U Murthy
2015-04-14  8:10     ` Shreyas B Prabhu
2015-04-14  8:31       ` Preeti U Murthy
2015-04-14  8:27   ` Preeti U Murthy
2015-04-15  6:05     ` Shreyas B Prabhu [this message]

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