Re: [PATCH] gpio: siox: potentially enabling IRQs too early

[Thomas Gleixner <tglx@xxxxxxxxxxxxx>]

Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> writes:
> On Tue, Feb 11, 2020 at 10:35:44AM +0300, Dan Carpenter wrote:
>> Smatch thinks that gpio_siox_irq_set_type() can be called from
>> probe_irq_on().  In that case the call to spin_unlock_irq() would
>> renable IRQs too early.
>> 
>> Fixes: be8c8facc707 ("gpio: new driver to work with a 8x12 siox")
>> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
>> ---
>>  drivers/gpio/gpio-siox.c | 5 +++--
>>  1 file changed, 3 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/gpio/gpio-siox.c b/drivers/gpio/gpio-siox.c
>> index 311f66757b92..578b71760939 100644
>> --- a/drivers/gpio/gpio-siox.c
>> +++ b/drivers/gpio/gpio-siox.c
>> @@ -133,10 +133,11 @@ static int gpio_siox_irq_set_type(struct irq_data *d, u32 type)
>>  	struct irq_chip *ic = irq_data_get_irq_chip(d);
>>  	struct gpio_siox_ddata *ddata =
>>  		container_of(ic, struct gpio_siox_ddata, ichip);
>> +	unsigned long flags;
>>  
>> -	spin_lock_irq(&ddata->irqlock);
>> +	spin_lock_irqsave(&ddata->irqlock, flags);
>>  	ddata->irq_type[d->hwirq] = type;
>> -	spin_unlock_irq(&ddata->irqlock);
>> +	spin_unlock_irqrestore(&ddata->irqlock, flags);
>
> "Normally" the .irq_set_type() callback is called from irq_set_irq_type.
> There desc->lock is taken with raw_spin_lock_irqsave (as part of
> irq_get_desc_buslock()), so I assume irqs are always disabled when the
> type changes? tglx?
>
> If so, the better fix would be to change to spin_lock/spin_unlock
> instead. Also given that a raw spinlock is taken, the irqlock here
> should be changed to a raw one, too?

Indeed. Looking at the driver, all of the spin_lock_irq() usage in the
irqchip callbacks is broken.

So this needs two changes:

   1) Convert to raw spin lock, as this won't work on RT otherwise

   2) s/lock_irq/lock/ for all irqchip callbacks.

Thanks,

        tglx