Messages in this thread | | | Date | Fri, 26 Mar 2004 21:45:07 +0100 | From | Edgar Toernig <> | Subject | Re: [PATCH] Consolidate multiple implementations of jiffies-msecs conversions. |
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Sridhar Samudrala wrote: > > On Fri, 26 Mar 2004, Edgar Toernig wrote: > > > Sridhar Samudrala wrote: > > > > > >[...] > > > -#define MSECS(ms) (((ms)*HZ/1000)+1) > > > -return (((ms)*HZ+999)/1000); > > > +return (msecs / 1000) * HZ + (msecs % 1000) * HZ / 1000; > > > > Did you check that all users of the new version will work correctly > > with your rounding? Explicit round-up of delays is often required, > > especially when talking to hardware... >[...] > I guess you are referring to cases when HZ < 1000(ex: 100) and msecs is > less than 10. In those cases, the new version returns 0, whereas some of the > older versions return 1.
Exactly - but not only <10. Any value that is not exactly representable in jiffies. I.e. for a delay of 15ms one has to wait 2 jiffies on a 100HZ system. Your version would give 1 jiffy = 10ms -- too short.
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