On Thu, Sep 18, 2014 at 3:46 PM, Johan Hovold <johan@xxxxxxxxxx> wrote: > On Thu, Sep 18, 2014 at 03:43:07PM +0300, Octavian Purdila wrote: >> On Thu, Sep 18, 2014 at 1:54 PM, Johan Hovold <johan@xxxxxxxxxx> wrote: >> > On Tue, Sep 09, 2014 at 10:24:46PM +0300, Octavian Purdila wrote: > >> > Either way, it looks like this could race with get_direction() if you >> > get a set_direction() while get_direction() is retrieving the direction >> > from the device. >> > >> > This would break gpio_get(). >> > >> I don't think gpio_set_direction() and gpio_get() are allowed to race. > > I wrote that set_direction() and get_direction() could race, which in > turn would break gpio_get() as you would be caching the wrong > direction setting. > OK, I now see the problem. I think doing this in get_direction() will fix the issue: if (!test_and_set_bit(offset, dln2->pin_dir_set)) set/clear_bit(offset, dln2->pin_dir); because gpiolib calls get_direction() while requesting a pin and request cannot race with itself. Which means that get_direction() can not race with itself the first time it is called, when the set/clear operation will be run. And because we know that get_direction() is called first, we can even remove the set/clear operation from set_direction(). -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html