Messages in this thread Patch in this message | | | Date | Fri, 23 May 2014 02:43:31 +0530 | From | "Srivatsa S. Bhat" <> | Subject | Re: [PATCH] x86, MCE: Kill CPU_POST_DEAD |
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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; > } >
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