Message-ID: <52F9CAAE.4020308@linux.vnet.ibm.com>
Date: Tue, 11 Feb 2014 12:31:02 +0530
From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
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        Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
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Subject: Re: [PATCH 26/51] x86, oprofile, nmi: Fix CPU hotplug callback registration
References: <20140205220251.19080.92336.stgit@srivatsabhat.in.ibm.com> <20140205220921.19080.94715.stgit@srivatsabhat.in.ibm.com> <20140210190737.GD3416@in.ibm.com> <20140210192747.GE3416@in.ibm.com>
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On 02/11/2014 12:57 AM, Gautham R Shenoy wrote:
> On Tue, Feb 11, 2014 at 12:37:37AM +0530, Gautham R Shenoy wrote:
>> Hi,
>>
>> On Thu, Feb 06, 2014 at 03:39:22AM +0530, Srivatsa S. Bhat wrote:
>>> Fix the oprofile code in x86 by using this latter form of callback
>>> registration. But retain the calls to get/put_online_cpus(), since they
>>> also protect the variables 'nmi_enabled' and 'ctr_running'.
>>
>> get/put_online_cpus() protect us against cpu_hotplug_begin/end(). The
>> latter is always nested inside cpu_maps_update_begin/end(), which we
>> are already using here. 
>>
>> So what additional protection are we getting by retaining
>> get/put_online_cpus() ?
> 
> Probably you mean to say that there are other places which access
> 'nmi_enabled' and 'ctr_running' with the cpu-hotplug protection
> provided only by get/put_online_cpus() and you are retaining the calls
> in this patch to be consistent with those other places.

Yep, exactly!

> If so, could
> you reword the changelog to reflect this instead of saying "they also
> protect the variables ..." ?
>

Ok, will do! Thanks a lot!
 
Regards,
Srivatsa S. Bhat

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