Messages in this thread | | | Date | Wed, 5 Nov 2008 20:11:27 +0100 | From | Jens Axboe <> | Subject | Re: [PATCH 1/2] Add round_jiffies_up and related routines |
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On Wed, Nov 05 2008, Alan Stern wrote: > On Wed, 5 Nov 2008, Tejun Heo wrote: > > > Alan Stern wrote: > > > This patch (as1158) adds round_jiffies_up() and friends. These > > > routines work like the analogous round_jiffies() functions, except > > > that they will never round down. > > > > > > The new routines will be useful for timeouts where we don't care > > > exactly when the timer expires, provided it doesn't expire too soon. > > > > > > Signed-off-by: Alan Stern <stern@rowland.harvard.edu> > > > > Heh... I have exactly the same patches but mines were named > > round_up_jiffies(). > > To an American, "round_up_jiffies" sounds like something a cowboy might > do. :-) > > I haven't bothered to look throughout the kernel to see where > round_jiffies_up() could be used. Have you done this?
Heh, I do agree :-)
> > > + unsigned long j0 = jiffies; > > > + > > > + barrier(); /* Prevent the compiler from aliasing j0 and jiffies */ > > > + return round_jiffies_common(j + j0, cpu, false) - j0; > > > > jiffies is volatile. No need for explicit barrier, > > I didn't realize that. Good, it makes things easier. > > > but this part is > > necessary for correct operation as if jiffies go up by two the > > calculation will wrap and the returned value will be very large. I > > think this fix deserves a separate patch and proper explanation. > > How about if I remove the barrier() call? Should this new code still > go in a separate patch?
I think it's fine as-is without the barrier. Can you resend it as such, makes it easier to merge up (plus, it does need a new signed-off-by).
-- Jens Axboe
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