Messages in this thread | | | Date | Wed, 6 May 2015 14:43:07 -0700 | Subject | Re: [RFC][PATCH v2] ktime: Fix ktime_divns to do signed division | From | John Stultz <> |
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On Wed, May 6, 2015 at 1:11 PM, Nicolas Pitre <nicolas.pitre@linaro.org> wrote: > On Wed, 6 May 2015, John Stultz wrote: > >> It was noted that the 32bit implementation of ktime_divns() >> was doing unsigned division and didn't properly handle >> negative values. >> >> This patch fixes the problem by checking and preserving >> the sign bit, and then reapplying it if appropriate after >> the division, it also changes the return type to a s64 >> to make it more obvious this is expected. >> > [...] >> >> -# define ktime_divns(kt, div) (u64)((kt).tv64 / (div)) >> +static inline s64 ktime_divns(const ktime_t kt, s64 div) >> +{ >> + /* >> + * 32-bit implementation cannot handle negative divisors, >> + * so catch them on 64bit as well. >> + */ >> + BUG_ON(div < 0); >> + return (u64)((kt).tv64 / (div)) > > You forgot to remove the u64 cast?
Thanks for catching that!
> Is there a reason why it was there originally?
I assume because nanoseconds are usually though of as unsigned. It was introduced way back in the original hrtimer core code: c0a3132963db68f1fbbd0e316b73de100fee3f08
thanks -john
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