Am 14.12.2012 15:34, schrieb Lars-Peter Clausen: > On 12/14/2012 03:29 PM, Alexander Holler wrote: >> Am 14.12.2012 15:15, schrieb Alexander Holler: >>> Am 14.12.2012 14:08, schrieb Alexander Holler: >>>> Am 14.12.2012 10:42, schrieb Lars-Peter Clausen: >>> >>>>> And another thing I've overlooked before: >>>>> wait_for_completion_interruptible_timeout can either return a positive >>>>> number when the completion was completed, 0 in case of an timeout, or a >>>>> negative error code in case it was interrupted. You need to handle all >>>>> three. E.g. something like this. >>>>> >>>>> ret = wait_for_completion_interruptible_timeout(...) >>>>> if (ret == 0) >>>>> return -EIO; >>>>> if (ret < 0) >>>>> return ret >>>>> >>>> >>>> Hmpf, the only working approach to use some in kernel functions really >>>> is to the read source yourself and don't trust anything else. :/ >>> >>> Anyway, my approach doesn't work as it introduces a race condition: >>> >>> >>> /* get a report with all values through requesting one value */ >>> sensor_hub_input_attr_get_raw_value(...) >>> >>> /* race if this task goes to slepp and the values were >>> received before it could call the below wait... >>> >>> /* wait for all values (event) */ >>> if (!wait_for_completion_interruptible_timeout(...)) >>> >>> >>> I'll have to look for a mechanism how to avoid that. So v5 might need >>> some time. >> >> Sorry for the noise. That INIT_COMPLETION() before the sensor...() does >> exactly that. So it's enough if I handle the different return situations of >> wait_for...(). >> >> I will just use if(wait...()<=0) return -EIO. >> > > No, that's wrong. You should really return the error code returned by > wait_for_completion_interruptible_timeout(). This will make sure that > userspace restarts the syscall if necessary. Sorry for my ignorance, but which reasons for interruption do exist which doesn't kill the userspace too? The error number -ESYSRESTART doesn't offer a hint. Alexander -- 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
