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Date: Tue, 22 Jul 2008 00:58:52 -0400 From: David Woodhouse <dwmw2@...radead.org> To: Nick Piggin <nickpiggin@...oo.com.au> Cc: linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>, arjan@...radead.org Subject: Re: [RFC] schedule_timeout_range() On Tue, 2008-07-22 at 14:50 +1000, Nick Piggin wrote: > On Tuesday 22 July 2008 14:45, David Woodhouse wrote: > > On Tue, 2008-07-22 at 14:33 +1000, Nick Piggin wrote: > > > The only thing I dislike about explicit times is that when a driver or > > > someone doesn't _really_ know how much to specify. Do you say 10s, 100s? > > > > This is true, but they certainly have a _better_ idea than we do. If the > > individual callers can't even come up with an answer, how are we ever > > going to come up with a generic policy that does the right thing? > > OK, how about still having a never-until-machine-is-already-awake? For timers we have that already -- it's called a deferrable timer. All I've done to create the 'range timer' is couple that with a normal timer, to implement the 'some time between X and Y' behaviour in a fashion which is simple for people to use. I did add the 'never-until-machine-is-already-awake' behaviour you request to schedule_timeout_range() -- you get it by setting 'timeout' to your intended minimum time, and setting the other argument (which was called 'deadline' in my original patch) to MAX_SCHEDULE_TIMEOUT. > > I really don't think that applying this kind of policy in generic code > > is useful -- I'd like the callers to provide numbers even if they _do_ > > pull it out of their wossname. > > > > The number they provide is the _maximum_ amount of time they should be > > prepared to wait (let's assume for a moment that they stayed sober and > > remembered Linux isn't a real-time kernel, so all guarantees are taken > > with a pinch of salt. Let's not get bogged down in nomenclature). > > Well, I think it is still wise to avoid words like deadline, hard, > and timeout in the same sentence ;) Probably true :) > > In practice, they'll almost always get called before that maximum time > > expires -- that's the whole _point_, of course. But we can't _invent_ > > that maximum in generic code; that's really up to the caller. > > Not a maximum, but just an "I don't know... a lot?" define. But yeah > I guess there aren't too many good reasons for that. I'd really like to avoid it. It puts the responsibility for coming up with a number a _long_ way from where it should be, in the individual caller. -- David Woodhouse Open Source Technology Centre David.Woodhouse@...el.com Intel Corporation -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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