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SubjectRe: [PATCH] x86, MCE: Kill CPU_POST_DEAD
On 05/23/2014 01:25 AM, Borislav Petkov wrote:
> On Thu, May 22, 2014 at 03:50:21PM +0000, Luck, Tony wrote:
>>>> So I think we can reduce it to just the one rwsem (with recursion) if we
>>>> shoot CPU_POST_DEAD in the head.
>>>
>>> Here's the first bullet. Stressing my box here with Steve's hotplug
>>> script seems to work fine.
>>>
>>> Tony, any objections?
>>
>> what was this comment referring to:
>>
>> /* intentionally ignoring frozen here */
>>
>> After you move the cmci_rediscover() call, it is now in a place where we are
>> no longer ignoring frozen (i.e. the old placement did the rediscover even if the
>> CPU_TASKS_FROZEN bit was set - with the new placement we will skip rediscovery.
>>
>> So we were working around some interaction between cpu hotplug and frozen.
>> Do we no longer need to do that?
>
> Hmm, that FROZEN thing is supposedly for hotplug operations while
> suspend is happening. I guess it makes a little sense to rediscover CMCI
> banks while suspend is in progress. Whatever.
>
> Let's keep it before more crap ensues, that was a good catch, thanks.
>
> So, I guess something like that instead.
>
> Which means, I'd need to run a couple of suspend/resume rounds while
> hotplugging cores to see whether we're still kosher.
>
> More fun tomorrow.
>
> ---
> From: Borislav Petkov <bp@suse.de>
> Date: Thu, 22 May 2014 16:40:54 +0200
> Subject: [PATCH] x86, MCE: Kill CPU_POST_DEAD
>
> In conjunction with cleaning up CPU hotplug, we want to get rid of
> CPU_POST_DEAD. Kill this instance here and rediscover CMCI banks at the
> end of CPU_DEAD.
>
> Signed-off-by: Borislav Petkov <bp@suse.de>

Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>

Regards,
Srivatsa S. Bhat

> ---
> arch/x86/kernel/cpu/mcheck/mce.c | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
> index 68317c80de7f..bfde4871848f 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> @@ -2391,6 +2391,10 @@ mce_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
> threshold_cpu_callback(action, cpu);
> mce_device_remove(cpu);
> mce_intel_hcpu_update(cpu);
> +
> + /* intentionally ignoring frozen here */
> + if (!(action & CPU_TASKS_FROZEN))
> + cmci_rediscover();
> break;
> case CPU_DOWN_PREPARE:
> smp_call_function_single(cpu, mce_disable_cpu, &action, 1);
> @@ -2402,11 +2406,6 @@ mce_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
> break;
> }
>
> - if (action == CPU_POST_DEAD) {
> - /* intentionally ignoring frozen here */
> - cmci_rediscover();
> - }
> -
> return NOTIFY_OK;
> }
>




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