Re: [PATCH 06/11] ACPI / gsi: Add gsi_mutex to synchronize acpi_register_gsi()/acpi_unregister_gsi()

[Hanjun Guo]

On 06/10/2015 11:58 PM, Marc Zyngier wrote:
> On 18/05/15 13:59, Hanjun Guo wrote:
> > Add a mutex for acpi_register_gsi()/acpi_unregister_gsi() to avoid
> > concurrency issues.
> >
> > Signed-off-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
> > ---
> >   drivers/acpi/gsi.c | 17 +++++++++++++----
> >   1 file changed, 13 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/acpi/gsi.c b/drivers/acpi/gsi.c
> > index 55b5f31..ab0dcb4 100644
> > --- a/drivers/acpi/gsi.c
> > +++ b/drivers/acpi/gsi.c
> > @@ -16,6 +16,7 @@
> >   enum acpi_irq_model_id acpi_irq_model;
> >   /* ACPI core domian pointing to GICv2/3 core domain */
> >   struct irq_domain *acpi_irq_domain __read_mostly;
> > +static DEFINE_MUTEX(gsi_mutex);
> >
> >   static unsigned int acpi_gsi_get_irq_type(int trigger, int polarity)
> >   {
> > @@ -73,20 +74,24 @@ int acpi_register_gsi(struct device *dev, u32 gsi, int trigger,
> >   	int irq;
> >   	unsigned int irq_type = acpi_gsi_get_irq_type(trigger, polarity);
> >
> > +	mutex_lock(&gsi_mutex);
> >   	irq = irq_find_mapping(acpi_irq_domain, gsi);
> >   	if (irq > 0)
> > -		return irq;
> > +		goto out;
> >
> >   	irq = irq_domain_alloc_irqs(acpi_irq_domain, 1, dev_to_node(dev),
> >   				    &gsi);
> >   	if (irq <= 0)
> > -		return -EINVAL;
> > +		goto out;
> >
> >   	/* Set irq type if specified and different than the current one */
> >   	if (irq_type != IRQ_TYPE_NONE &&
> >   		irq_type != irq_get_trigger_type(irq))
> >   		irq_set_irq_type(irq, irq_type);
> > -	return irq;
> > +
> > +out:
> > +	mutex_unlock(&gsi_mutex);
> > +	return irq > 0 ? irq : -EINVAL;
> >   }
> >   EXPORT_SYMBOL_GPL(acpi_register_gsi);
> >
> > @@ -96,8 +101,12 @@ EXPORT_SYMBOL_GPL(acpi_register_gsi);
> >    */
> >   void acpi_unregister_gsi(u32 gsi)
> >   {
> > -	int irq = irq_find_mapping(acpi_irq_domain, gsi);
> > +	int irq;
> > +
> > +	mutex_lock(&gsi_mutex);
> > +	irq = irq_find_mapping(acpi_irq_domain, gsi);
> >
> >   	irq_dispose_mapping(irq);
> > +	mutex_unlock(&gsi_mutex);
> >   }
> >   EXPORT_SYMBOL_GPL(acpi_unregister_gsi);
>
> Can you point out why we need this locking? The rest of the kernel seems
> to live without it pretty well. And if we really have an issue, I'd

Hmm, I'm not so sure, I will look deep into that and come back later.

> prefer seeing it fixed in the core code rather than in something that is
> very much firmware-specific.

I agree if there are real issues.

Thanks
Hanjun
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