From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
To: Borislav Petkov <bp@alien8.de>,
"Luck, Tony" <tony.luck@intel.com>,
Andi Kleen <andi@firstfloor.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
Jacob Pan <jacob.jun.pan@linux.intel.com>,
LKML <linux-kernel@vger.kernel.org>, Borislav Petkov <bp@suse.de>,
Ingo Molnar <mingo@kernel.org>,
"Wysocki, Rafael J" <rafael.j.wysocki@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
"ego@linux.vnet.ibm.com" <ego@linux.vnet.ibm.com>,
Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PATCH] x86, MCE: Kill CPU_POST_DEAD
Date: Fri, 23 May 2014 02:43:31 +0530 [thread overview]
Message-ID: <537E687B.9080300@linux.vnet.ibm.com> (raw)
In-Reply-To: <20140522195538.GM4383@pd.tnic>
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.
>>
That's not quite true. The existing code already ignores FROZEN for all the cases,
by ignoring it at the top of the switch-case itself:
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_ONLINE:
[...]
break;
case CPU_DEAD:
if (threshold_cpu_callback)
threshold_cpu_callback(action, cpu);
mce_device_remove(cpu);
mce_intel_hcpu_update(cpu);
break;
Then I started wondering what the comment really meant, and commit 1a65f970d1
made things clear: its actually the _other_ way around! That is, cmci_rediscover()
didn't have to be invoked* during suspend/resume, so it was kept separate from
the rest.
* or maybe it was not _supposed_ to be invoked; I don't know which is the case..
the original commit 88ccbedd9 didn't explain that.
Either way, cmci_rediscover() doesn't seem to have any reason why it should
be called specifically in the POST_DEAD stage only. So I'm sure we can get rid
of that one way or other easily.
Regards,
Srivatsa S. Bhat
>> 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>
> ---
> 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;
> }
>
next prev parent reply other threads:[~2014-05-22 21:14 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-22 9:23 [PATCH] intel_rapl: Correct hotplug correction Borislav Petkov
2014-05-22 9:43 ` Srivatsa S. Bhat
2014-05-22 10:08 ` Borislav Petkov
2014-05-22 11:54 ` Srivatsa S. Bhat
2014-05-22 12:13 ` Borislav Petkov
2014-05-22 12:32 ` Peter Zijlstra
2014-05-22 15:30 ` [PATCH] x86, MCE: Kill CPU_POST_DEAD Borislav Petkov
2014-05-22 15:50 ` Luck, Tony
2014-05-22 19:55 ` Borislav Petkov
2014-05-22 21:13 ` Srivatsa S. Bhat [this message]
2014-05-22 21:31 ` Borislav Petkov
2014-05-22 21:40 ` Srivatsa S. Bhat
2014-05-22 21:43 ` Srivatsa S. Bhat
2014-05-26 20:01 ` Borislav Petkov
2014-05-22 21:31 ` [PATCH] intel_rapl: Correct hotplug correction Srivatsa S. Bhat
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