On Mon, Feb 11, 2013 at 4:28 AM, Alex Courbot <acour...@nvidia.com> wrote: > On 02/09/2013 07:34 PM, Grant Likely wrote: >> >> The debugfs files really need to hold the gpiolib spinlock before >> accessing the list. Otherwise chip addition/removal will cause an oops. >> >> Cc: Alexandre Courbot <acour...@nvidia.com> >> Cc: Linus Walleij <linus.wall...@linaro.org> >> Signed-off-by: Grant Likely <grant.lik...@secretlab.ca> > > > Tested-by: Alexandre Courbot <acour...@nvidia.com> > > Just wondering: if we manage to change this spinlock into a mutex in the > future, wouldn't it be better to acquire it only once in gpiolib_seq_start() > and release it in gpiolib_seq_stop()? > > Even though the protection introduced by this patch definitely improves the > situation, it seems to me that chips could still be removed while being > displayed by gpiolib_seq_show().
Probably, but need to first verify that the mutex won't end up getting held between read() syscalls. Otherwise it would be possible to block addition/removal by holding the file open. I cursory read of seq_file looks like ->stop() is always called, but I would appreciate someone more cluefull to give an opinion here. I've also got a draft patch that turns gpio chips into first-class kobjects which means we can do proper reference counting on them and prevent the structure from actually disappearing while other drivers still hold references. g. -- 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/
