On 03/16/2013 01:37 AM, Doug Anderson wrote: > On Fri, Mar 15, 2013 at 2:53 PM, Lars-Peter Clausen <lars@xxxxxxxxxx> 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). > I think you still need the mutex for serialization, otherwise the requests would just cancel each other out. Btw. what happens if you start a conversion while another is still in progress? Is it possible to abort a conversion? - Lars -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
