Re: [PATCH 4/4 v4] rtc: add rtc-driver for HID sensors of type time

[Alexander Holler]

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.

Regards,

Alexander
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