On 09/19/2007 07:22 AM, Trent Piepho wrote: > 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. I'd agree, although I'd suggest to at this point keep anything (in ad1848, cs4231 wants a similar setup in its mce_down) not completely trivial for after 1.0.15. > 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. This would appear to be the case yes. > 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. Also sounds sensible, and the irq spinlock the expected method. > 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. Guess we should be testing this, but generallt, "hand-off" would be the best policy yes. Rene. _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
