Re: [PATCH v3 3/5] acpi, apei, ghes: Introduce more generic mechanism to init/deinit GHES error notifications.

[Tomasz Nowicki]

On 13.06.2014 15:10, Robert Richter wrote:
> On 13.06.14 13:02:58, Tomasz Nowicki wrote:
>
> > @@ -811,6 +819,8 @@ static int ghes_notify_nmi(unsigned int cmd, struct pt_regs *regs)
> >   	int sev, sev_global = -1;
> >   	int ret = NMI_DONE;
> >
> > +	BUG_ON(!IS_ENABLED(ARCH_HAS_ACPI_APEI_NMI));
> > +
>
> Now that we have the ARCH_HAS_ACPI_APEI_NMI option, group nmi code,
> put it in an #ifdef ... and make function stubs for the !nmi case
> where necessary. That code should moved to patch #2. If an arch does
> not support nmi code, we don't want to compile it into the kernel.
>
> Also this patch is quit a bit large and should further split into
> moving functional code into separate functions and the introduction of
> the notifier setup. This makes review much easier.
>
> I did not yet took a deep look into your notifier framework, but I
> don't really see a reason for the dynamic collection of function
> pointers in ghes_notify_tab. See below.
>
> >   	raw_spin_lock(&ghes_nmi_lock);
> >   	list_for_each_entry_rcu(ghes, &ghes_nmi, list) {
> >   		if (ghes_read_estatus(ghes, 1)) {
> > @@ -875,10 +885,6 @@ out:
> >   	return ret;
> >   }
>
> > +static int ghes_notify_init_nmi(struct ghes *ghes)
> > +{
> > +	unsigned long len;
> > +	int status = 0;
> > +
> > +	len = ghes_esource_prealloc_size(ghes->generic);
> > +	ghes_estatus_pool_expand(len);
> > +	mutex_lock(&ghes_list_mutex);
> > +	if (list_empty(&ghes_nmi))
> > +		status = register_nmi_handler(NMI_LOCAL, ghes_notify_nmi, 0,
> > +					      "ghes");
> > +	list_add_rcu(&ghes->list, &ghes_nmi);
> > +	mutex_unlock(&ghes_list_mutex);
> > +
> > +	return status;
> > +}
> > +
> > +static void ghes_notify_remove_nmi(struct ghes *ghes)
> > +{
> > +	unsigned long len;
> > +
> > +	mutex_lock(&ghes_list_mutex);
> > +	list_del_rcu(&ghes->list);
> > +	if (list_empty(&ghes_nmi))
> > +		unregister_nmi_handler(NMI_LOCAL, "ghes");
> > +	mutex_unlock(&ghes_list_mutex);
> > +	/*
> > +	 * To synchronize with NMI handler, ghes can only be
> > +	 * freed after NMI handler finishes.
> > +	 */
> > +	synchronize_rcu();
> > +	len = ghes_esource_prealloc_size(ghes->generic);
> > +	ghes_estatus_pool_shrink(len);
> > +}
> > +
> > +static void ghes_init_nmi(void)
> > +{
> > +	if (!IS_ENABLED(ARCH_HAS_ACPI_APEI_NMI))
> > +		return;
> > +
> > +	init_irq_work(&ghes_proc_irq_work, ghes_proc_in_irq);
> > +	ghes_notify_tab[ACPI_HEST_NOTIFY_NMI].init_call = ghes_notify_init_nmi;
> > +	ghes_notify_tab[ACPI_HEST_NOTIFY_NMI].remove_call =
> > +							ghes_notify_remove_nmi;
> > +}
> > +
>
> So this is the only code of your whole patch set that actually changes
> an entry, and just one time only during nmi init. Thus, there is no
> need at all for ghes_notify_tab. Just create function stubs for
> ghes_notify_{init,remove}_nmi for the !nmi case with the error message
> in it and call the functions directly in the switch/cases.
>
> > +static struct ghes_notify_setup
> > +	ghes_notify_tab[ACPI_HEST_NOTIFY_RESERVED] = {
> > +		[ACPI_HEST_NOTIFY_POLLED]   = {"POLLED",
> > +					       ghes_notify_init_polled,
> > +					       ghes_notify_remove_polled},
> > +		[ACPI_HEST_NOTIFY_EXTERNAL] = {"EXT_IRQ",
> > +					       ghes_notify_init_external,
> > +					       ghes_notify_remove_external},
> > +		[ACPI_HEST_NOTIFY_LOCAL]    = {"LOCAL_IRQ", NULL, NULL},
> > +		[ACPI_HEST_NOTIFY_SCI]      = {"SCI",
> > +					       ghes_notify_init_sci,
> > +					       ghes_notify_remove_sci},
> > +		[ACPI_HEST_NOTIFY_NMI]      = {"NMI", NULL, NULL},
> > +		[ACPI_HEST_NOTIFY_CMCI]     = {"CMCI", NULL, NULL},
> > +		[ACPI_HEST_NOTIFY_MCE]      = {"MCE", NULL, NULL},
> > +};
>
> Again, just keep the switch/case statements in the probe and removal
> function and call the init/remove functions directly in them. This is
> much easier.
>
> If we need dynamic registration of handlers (which I don't see yet)
> for the error sources above we could do this with an acpi notify
> handler or so.

Without abstraction, notify handler registration seems to be overhead. I 
will modify code as you suggested. Thanks.

Tomasz
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