On 08/19/2013 09:08 PM, Jonathan Cameron wrote:
- I am still encountering "module in use" message when I am trying
to execute rmmod on a driver module after generic_buffer application
has been launched at least once. This is not specific only to my
implementation but also for lps331ap driver (the only one of the
remaining IIO drivers supporting triggers I am able to test
currently).
Umm.. I'm unsure, but it 'might' be something to do with the interrupt issues
that are firing the above warning (though I doubt it as the lps331ap isn't
suffering from that bug - as it currently stands in tree).
Check that all the sysfs entries are as one would expect (no trigger attached
or buffered enabled etc). Might be a bug in generic_buffer but I haven't
personally seen it do this.
Fixing the warning didn't fix this problem. I've checked sysfs entries
- the buffer is not enabled, no trigger is attached. I don't know if
this is correct, but when I build build my driver as a module I get
also the module industrialio-triggered-buffer.ko built, which has to
be loaded prior to the driver module.
That provides the triggered_buffer utility functions. When those are used
it needs to be there.
Unfortunately this isn't something I can chase down without the hardware.
It works fine in the iio_dummy driver. Could you perhaps just build that
and check that works fine with a sysfs-trigger? Would act to indicate
if there is something causing the issue in this driver that we haven't spotted
or something nasty is going on in the core.
I've managed to discover what is going on. The bad symptom is in the
information returned by lsmod. Before launching generic_buffer
application the "Used by" column for the driver module is 0.
After the application finishes it is 0x7fffffff.
I figured out that the problem is in the function
iio_trigger_write_current (industrialio-trigger.c:371).
If I comment lines:
if (oldtrig && indio_dev->trig != oldtrig)
iio_trigger_put(oldtrig);
the issue ceases to appear. It seems that module_put is called too many
times.
Thanks,
Jacek
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