On Friday, March 27, 2015 8:13 AM, Ian Abbott wrote: > `comedi_event()` is called from low-level drivers to handle comedi > asynchronous command event flags. As a safety check, it checks the > subdevice's "run" flags to make sure an asynchronous command is running. > It can also change the run flags to mark the command as no longer > running (possibly also marking it as terminated with an error). > Checking the runflags and modifying them involves two uses of the > subdevice's spin-lock. It seems better to do it with a single use of > the spin-lock. This also avoids possible interactions with > `do_become_nonbusy()`. > > Acquire the subdevice's spin-lock at the start of `comedi_event()` and > release it near the end, before a possible call to `kill_fasync()` (but > after it's parameter values have been determined). > > Add and make use of few new inline helper functions: > > * `__comedi_clear_subdevice_runflags()` -- clears some run flags without > using the spin-lock > * `__comedi_set_subdevice_runflags()` -- sets some run flags without > using the spin-lock > * `__comedi_get_subdevice_runflags()` -- a spin-lockless version of > `comedi_get_subdevice_runflags() > * `__comedi_is_subdevice_running()` -- a spin-lockless version of > * `comedi_is_subdevice_running()` > > Signed-off-by: Ian Abbott <abbo...@mev.co.uk>
Ian, For completeness, the comedi_alloc_spriv() helper should probably use __comedi_set_subdevice_runflags() to set the COMEDI_SRF_FREE_SPRIV bit. Regards, Hartley -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
