Re: [PATCH] gpiolib: handle probe deferrals better

[Alexander Stein <alexander.stein@xxxxxxxxxxxxxxxxxxxxx>]

On Thursday 07 April 2016 19:09:06, Linus Walleij wrote:
> >>> 4) irq_ready access synchronization on SMP? atomic?
> >> 
> >> Uhhh.... I don't even understand the question.
> > 
> > in my patch the irq_ready is set from _gpiochip_irqchip_add() and
> > read from gpiod_request() without any kind of protection and those
> > two functions can be executed in parallel.
> 
> Aha. Well I don't know if that is really a big problem?
> Does that really happen in practice?

I guess this is what actually happens in my case. The gpio controller has 
already been registred and the companion irq chip is about to be registered.
Meanwhile gpio-keys requests a GPIO from that recently registred gpio 
controller and the following gpio_to_irq or irq_request returns 0 or fails as 
the irq chip has not been registred yet (without Grygorii's patch). So this 
calling situation might actually happen.

Best regards,
Alexander

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