On Wed 2015-07-01 09:28:52, Jacek Anaszewski wrote: > On 06/30/2015 07:46 PM, Pavel Machek wrote: > >On Tue 2015-06-30 15:06:19, Jacek Anaszewski wrote: > >>On 06/30/2015 01:58 PM, Pavel Machek wrote: > >>>On Tue 2015-06-30 10:01:08, Jacek Anaszewski wrote: > >>>>This patch rearranges the core LED subsystem code, so that it > >>>>now removes from drivers the responsibility of using work queues > >>>>internally in case their brightness_set ops can sleep. > >>>>Addition of two flags: LED_BRIGHTNESS_FAST and LED_BLINK_DISABLE > >>>>as well as new_brightness_value property to the struct led_classdev > >>>>allows for employing existing set_brightness_work to do the job. > >>>>The modifications allow also to get rid of brightness_set_sync op, > >>>>as flash LED devices can now be handled properly only basing on the > >>>>SET_BRIGHTNESS_SYNC flag. > >>> > >>>Are you sure this is good idea? > >>> > >>>You'll now use single callback for blocking and non-blocking > >>>behaviour. I'm pretty sure stuff like lockdep will have some fun with > >>>that. > >> > >>I enabled "Lock Debugging" options and didn't get any warning. > >>Could you describe the use case you are thinking of? > > > >You may get one when one of the sleeping functions uses some lock... > > Drivers which use spin_lock in their brightness_set op will have to > set LED_BRIGHTNESS_FAST flag, which will instruct the LED core to > call the op synchronously. On the other hand drivers which can sleep > in their brightness_set op won't set the flag, which will make LED core > delegating the op to the work queue task. It is also possible that > driver with brightness_set op that can sleep set SET_BRIGHTNESS_SYNC > flag - then LED core will call it in a synchronous way from > led_brightness_set and it will schedule work queue task in case > the op is called from triggers. I understand this "works". > If you want to NAK the patch, please come up with detailed analysis > on how it can cause problems. Without this I infer that you didn't > spend a second on analyzing the code. This is counterproductive. NAK. Because calling two functions with different semantics through same function pointer is extremely ugly, and _will_ cause lockdep problems. Talk to the lockdep people for details. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-leds" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
