On 08/07/2017 05:56 AM, Marc Zyngier wrote: > On 28/07/17 15:06, Marc Gonzalez wrote: >> On 27/07/2017 20:17, Florian Fainelli wrote: >> >>> On 07/26/2017 12:13 PM, Måns Rullgård wrote: >>> >>>> Florian Fainelli writes: >>>> >>>>> On 07/25/2017 06:29 AM, Måns Rullgård wrote: >>>>> >>>>>> Marc Gonzalez <marc_gonza...@sigmadesigns.com> writes: >>>>>> >>>>>>> On 25/07/2017 15:16, Måns Rullgård wrote: >>>>>>> >>>>>>>> What happened to the patch adding the proper combined function? >>>>>>> >>>>>>> It appears you're not CCed on v2. >>>>>>> >>>>>>> https://patchwork.kernel.org/patch/9859799/ >>>>>>> >>>>>>> Doug wrote: >>>>>>>> Yes, you understand correctly. The irq_mask_ack method is entirely >>>>>>>> optional and I assume that is why this issue went undetected for so >>>>>>>> long; however, it is slightly more efficient to combine the functions >>>>>>>> (even if the ack is unnecessary) which is why I chose to do so for my >>>>>>>> changes to the irqchip-brcmstb-l2 driver where I first discovered this >>>>>>>> issue. How much value the improved efficiency has is certainly >>>>>>>> debatable, but interrupt handling is one area where people might care >>>>>>>> about such a small difference. As the irqchip-tango driver maintainer >>>>>>>> you are welcome to decide whether or not the irq_mask_ack method makes >>>>>>>> sense to you. >>>>>>> >>>>>>> My preference goes to leaving the irq_mask_ack callback undefined, >>>>>>> and let the irqchip framework use irq_mask and irq_ack instead. >>>>>> >>>>>> Why would you prefer the less efficient way? >>>>>> >>>>> >>>>> Same question here, that does not really make sense to me. >>>>> >>>>> The whole point of this patch series is to have a set of efficient and >>>>> bugfree (or nearly) helper functions that drivers can rely on, are you >>>>> saying that somehow using irq_mask_and_ack is exposing a bug in the >>>>> tango irqchip driver and using the separate functions does not expose >>>>> this bug? >>>> >>>> There is currently a bug in that the function used doesn't do what its >>>> name implies which can't be good. Using the separate mask and ack >>>> functions obviously works, but combining them saves a lock/unlock >>>> sequence. The correct combined function has already been written, so I >>>> see no reason not to use it. >>> >>> Marc/Mason, are you intending to get this patch accepted in order to >>> provide a quick bugfix targeting earlier kernels with the tango irqchip >>> driver or is this how you think the correct fix for the tango irqchip >>> driver is as opposed to using Doug's fix? >> >> Hello Florian, >> >> I am extremely grateful for you and Doug bringing the defect to >> my attention, as it was indeed causing an issue which I had not >> found the time to investigate. >> >> The reason I proposed an alternate patch is that >> 1) Doug didn't seem to mind, 2) simpler code leads to fewer bugs >> and less maintenance IME, and 3) I didn't see many drivers using >> the irq_mask_ack() callback (9 out of 86) with a few misusing it, >> by defining irq_mask = irq_mask_ack. >> >> As you point out, my patch might be slightly easier to backport >> than Doug's (TBH, I hadn't considered that aspect until you >> mentioned it). >> >> Has anyone ever quantified the performance improvement of >> mask_ack over mask + ack? > > Aren't you the one who is in position of measuring this effect on the > actual HW that uses this?
What do we do with this patch series to move forward? Can we get Doug's changes queued up for 4.14? -- Florian
