At Tue, 18 Sep 2007 22:22:42 -0700 (PDT), Trent Piepho wrote: > > New thread for the the final version of the patches for my fixes to the ad1848 > auto-calibration loop. I made a couple suggested changes. These should be ok > to apply, and should be independent of the other as yet un-applied patches > that have been posted by Rene and Krzysztof. OK, I merged them to HG tree now. Thanks. > I'm not an expert on this chip by any means, but from looking at the code I > think there are few things that could be fixed. > > The reg_lock spinlock isn't acquired from the irq handler, as the handler > doesn't use any of the indirect registers. I think this means that is isn't > necessary to use the irq disabling versions of the spin_lock functions with > reg_lock. > > It does look like there is a different SMP race condition wrt the irq handler. > >From snd_ad1848_interrupt(): > 578 if ((chip->mode & AD1848_MODE_PLAY) && chip->playback_substream && > 579 (chip->mode & AD1848_MODE_RUNNING)) > 580 snd_pcm_period_elapsed(chip->playback_substream); > > Another CPU could close the substream between the check and the call to > snd_pcm_period_elapsed(). snd_pcm_period_elapsed() could be called with > either NULL or a stale substream pointer depending on how the code compiled. > I'd think creating an irq spinlock would be an easy way to fix this. The irq > handler would grab it, and the same with the open() and close() functions > around the code that sets the substream pointers. Alternatively, one could > disabled the irq handler during open and close. Yes, it'd be an easy solution. > I think there might also be problem with setting mixers controls during > auto-calibration . While waiting for auto-calibration to finish, the chip > isn't locked. If another thread tries to set the volume via the mixer > interface, it won't be blocked and will try to talk to the chip during AC. > The datasheet just says to wait for auto-calibration to finish, it doesn't say > what happens if you don't. So maybe there isn't any problem here. Hm, this may happen, too. Anyway, let's do more cleanups after 1.0.15 release. Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
