linux-kernel - Re: [PATCH 5/7] x86/mcheck: reorganize the hotplug callbacks

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Date:   Fri, 11 Nov 2016 20:36:31 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-kernel@...r.kernel.org, tglx@...utronix.de, rt@...utronix.de,
        Tony Luck <tony.luck@...el.com>, linux-edac@...r.kernel.org,
        x86@...nel.org
Subject: Re: [PATCH 5/7] x86/mcheck: reorganize the hotplug callbacks

On 2016-11-11 19:44:53 [+0100], Borislav Petkov wrote:
> > ---
> >  arch/x86/kernel/cpu/mcheck/mce.c | 31 +++++++++++++++----------------
> >  1 file changed, 15 insertions(+), 16 deletions(-)
> > 
> > diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
> > index 052b5e05c3c4..3da6fd94fa2e 100644
> > --- a/arch/x86/kernel/cpu/mcheck/mce.c
> > +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> > @@ -1771,6 +1771,9 @@ void (*machine_check_vector)(struct pt_regs *, long error_code) =
> >   */
> >  void mcheck_cpu_init(struct cpuinfo_x86 *c)
> >  {
> > +	struct timer_list *t = this_cpu_ptr(&mce_timer);
> > +	unsigned int cpu = smp_processor_id();
> > +
> >  	if (mca_cfg.disabled)
> >  		return;
> >  
> > @@ -1796,7 +1799,7 @@ void mcheck_cpu_init(struct cpuinfo_x86 *c)
> >  	__mcheck_cpu_init_generic();
> >  	__mcheck_cpu_init_vendor(c);
> >  	__mcheck_cpu_init_clear_banks();
> > -	__mcheck_cpu_init_timer();
> > +	setup_pinned_timer(t, mce_timer_fn, cpu);
> 
> Why not leave all that setup stuff in __mcheck_cpu_init_timer() ?
> 
__mcheck_cpu_init_timer() does not only prepare the timer but also fires
it. And __mcheck_cpu_init_timer() is invoked from other places and the
caller probably expects the timer to be fired.

> > @@ -2517,11 +2518,10 @@ mce_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
> >  			mce_device_remove(cpu);
> >  			return NOTIFY_BAD;
> >  		}
> > -
> > +		mce_reenable_cpu();
> > +		mce_start_timer(cpu, t);
> >  		break;
> >  	case CPU_DEAD:
> > -		mce_threshold_remove_device(cpu);
> > -		mce_device_remove(cpu);
> >  		mce_intel_hcpu_update(cpu);
> >  
> >  		/* intentionally ignoring frozen here */
> 
> There's another place for cpuhp_tasks_frozen replacement here:
> 
>                 /* intentionally ignoring frozen here */
>                 if (!(action & CPU_TASKS_FROZEN))
>                         cmci_rediscover();
> 
> into
> 
> 		if (!cpuhp_tasks_frozen)
> 			cmci_rediscover();

Correct. This is done later since it still works. For functions like
mce_disable_cpu() which were converted here I replaced the check so I
keep them void and don't care about the argument.

Sebastian