Simon Horman wrote: > On Tue, Oct 16, 2007 at 10:35:52PM +0900, Hidetoshi Seto wrote: >> +#define cputime_to_jiffies(__ct) ((__ct) * HZ / NSEC_PER_SEC) >> +#define jiffies_to_cputime(__jif) ((__jif) * NSEC_PER_SEC / HZ) >> +#define cputime64_to_jiffies64(__ct) ((__ct) * HZ / NSEC_PER_SEC) >> +#define jiffies64_to_cputime64(__jif) ((__jif) * NSEC_PER_SEC / HZ) > > It looks like cputime64_to_jiffies64 and cputime_to_jiffies will > overflow at (((2^64 -1) / HZ) + 1) ns. In the case where HZ is 1000, > this means it will overflow at (584/1000) years or about 213 days. > Similarly for cputime_to_clock_t(). Is this a problem? Exactly. I guess NSEC_PER_SEC is permanently 10^9, and larger HZ will not be required soon in this century. Does the following help us? #define cputime64_to_jiffies64(__ct) ((__ct) / (NSEC_PER_SEC / HZ)) #define jiffies64_to_cputime64(__jif) ((__jif) * (NSEC_PER_SEC / HZ)) Thanks, H.Seto - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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