Messages in this thread | | | Date | Fri, 15 Mar 2013 17:37:54 -0700 | Subject | Re: [RFC: PATCH 2/2] iio: adc: exynos_adc: Handle timeout and race conditions | From | Doug Anderson <> |
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On Fri, Mar 15, 2013 at 2:53 PM, Lars-Peter Clausen <lars@metafoo.de> wrote: > What exactly is the spinlock protecting against here? Concurrent runs of > exynos_adc_isr? This is probably not issue in the first place. > > What you want to protect against is that completion is completed between the > call to INIT_COMPLETION() and the start of a new conversion. So the sections > that need to be under the spinlock are the complete call here and the point > from INIT_COMPLETION until the transfer is started in exynos_read_raw(). Make > sure to use spin_lock_irq there.
...and at that point I _think_ you won't also need the mutex.
A reasonable way to test to see if you've got this all correct would be to:
* Start two processes that are reading from different ADCs that will report very different values (maybe add a device tree node for adc1 or adc7 and use those since they're not really connected to thermistors?).
* Have your two processes read as fast as they can. This could just be "while true; do cat /sys/class/hwmon/hwmon0/device/temp1_input; done"
* Decrease your timeout and maybe(?) sprinkle some random udelays in the irq handler so that the timeouts happen sometimes but not others.
* Periodically cancel one of the readers with Ctrl-C
If all is working well then you should always get back the right value from the right reader (and get no crashes).
-Doug
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