Re: [PATCH 13/33] wait: add wait_event_hrtimeout()

[Theodore Ts'o]

On Thu, Mar 21, 2013 at 09:35:34AM -0700, Kent Overstreet wrote:
> Analagous to wait_event_timeout() and friends, this adds
> wait_event_hrtimeout() and wait_event_interruptible_hrtimeout().
> 
> Note that unlike the versions that use regular timers, these don't return
> the amount of time remaining when they return - instead, they return 0 or
> -ETIME if they timed out.  because I was uncomfortable with the semantics
> of doing it the other way (that I could get it right, anyways).
> 
> If the timer expires, there's no real guarantee that expire_time -
> current_time would be <= 0 - due to timer slack certainly, and I'm not
> sure I want to know the implications of the different clock bases in
> hrtimers.
> 
> If the timer does expire and the code calculates that the time remaining
> is nonnegative, that could be even worse if the calling code then reuses
> that timeout.  Probably safer to just return 0 then, but I could imagine
> weird bugs or at least unintended behaviour arising from that too.
> 
> I came to the conclusion that if other users end up actually needing the
> amount of time remaining, the sanest thing to do would be to create a
> version that uses absolute timeouts instead of relative.

Reviewed-by: "Theodore Ts'o" <tytso@xxxxxxx>

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