On Mon, 29 Jun 2020, Giuliano Pochini wrote: > On Fri, 19 Jun 2020 22:21:54 +0100 (BST) > Mark Hills <mark@xxxxxxxx> wrote: > > > On Fri, 19 Jun 2020, Giuliano Pochini wrote: > > > > > On Wed, 17 Jun 2020 12:14:42 +0100 (BST) > > > Mark Hills <mark@xxxxxxxx> wrote: > > > > > [...] > > > > You might be able to do the comparison before wrapping pipe_position, > > > > but hopefully you'll consider my patch in reply to Takashi has more > > > > clarity. > > > > > > Your patch is very interesting. I didn't take into account the idea of > > > advancing the position by full periods only. If the PCM subsystem > > > hasn't changed much since I last checked (I wrote the driver many years > > > ago), it should work fine (and I'm sure you tested it). But I don't > > > know if something else requires better resolution. > > > > It's funny, but I didn't take account of the opposite; that there was any > > merits to polling inbetween the interrupts for better resolution. > > > > Takashi pointed out the need for this and we had some discussion. Check > > the other thread, where I provided a newer revision of the code. > > > > The good thing is I think we can have all the things we want and be bug > > free, just I have to understand the specification. > > > > It would be great if you would like to take a look at the newer code for > > any problems you can see. I was going to run it for a few days then turn > > it into some patches. > > I looked at your code and I think it's OK. I'm using it for some days > without any problem. I also stressed it with pretty tight timings and it > worked fine all the time. > > Since I could not reproduce that problem before, except in some rare > random circumstances, I'm not a good tester at all. At most I can say > that your patch does not make things worse :) What software are you using on the device, and are you using x86_64 and dmix? I think some issues might be exaggerated by dmix which has a unique way of opening the device several times. And then chromium exercises dmix a lot with all of its threads/forks. That would I presume be how it exercises races between pcm_pointer and interrupts. -- Mark
