Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH 2/9] timer: Add comments about calc_index() ceiling work | Date | Tue, 14 Jul 2020 11:13:26 +0200 |
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Frederic Weisbecker <frederic@kernel.org> writes: > static inline unsigned calc_index(unsigned expires, unsigned lvl) > { > + /* > + * Time may have past since the clock last reached an index of > + * this @lvl. And that time, below LVL_GRAN(@lvl), is going to > + * be substracted from the delta until we reach @expires. To > + * fix that we must add one level granularity unit to make sure > + * we rather expire late than early. Prefer ceil over floor.
This comment confuses the hell out of me.
/* * The timer wheel has to guarantee that a timer does not fire * early. Early expiry can happen due to: * - Timer is armed at the edge of a tick * - Truncation of the expiry time in the outer wheel levels * * Round up with level granularity to prevent this. */
Hmm?
Thanks,
tglx
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