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SubjectRe: [PATCH v3] ktime: Fix ktime_divns to do signed division
On Fri, 8 May 2015, John Stultz wrote:
> +static inline s64 ktime_divns(const ktime_t kt, s64 div)
> {
> + /*
> + * Negative divisors could cause an inf loop,
> + * so bug out here.
> + */
> + BUG_ON(div < 0);
> if (__builtin_constant_p(div) && !(div >> 32)) {
> - u64 ns = kt.tv64;
> + s64 ns = kt.tv64;
> + int neg = (ns < 0);
> +
> + if (neg)
> + ns = -ns;
> do_div(ns, div);

This triggers the typecheck for u64 in do_div(). The delta patch below
should do the trick.

Thanks,

tglx

diff --git a/include/linux/ktime.h b/include/linux/ktime.h
index ab2de1c7932c..b9620ebe356f 100644
--- a/include/linux/ktime.h
+++ b/include/linux/ktime.h
@@ -177,13 +177,13 @@ static inline s64 ktime_divns(const ktime_t kt, s64 div)
if (__builtin_constant_p(div) && !(div >> 32)) {
s64 ns = kt.tv64;
int neg = (ns < 0);
+ u64 tmp;

if (neg)
ns = -ns;
- do_div(ns, div);
- if (neg)
- ns = -ns;
- return ns;
+ tmp = ns;
+ do_div(tmp, div);
+ return neg ? -tmp : tmp;
} else {
return __ktime_divns(kt, div);
}
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index c98ce4d9f613..bac65f810afd 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -268,8 +268,9 @@ lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
*/
s64 __ktime_divns(const ktime_t kt, s64 div)
{
- s64 dclc;
int neg, sft = 0;
+ s64 dclc;
+ u64 tmp;

dclc = ktime_to_ns(kt);
neg = (dclc < 0);
@@ -280,12 +281,9 @@ s64 __ktime_divns(const ktime_t kt, s64 div)
sft++;
div >>= 1;
}
- dclc >>= sft;
- do_div(dclc, (unsigned long) div);
- if (neg)
- dclc = -dclc;
-
- return dclc;
+ tmp = dclc >> sft;
+ do_div(tmp, (unsigned long) div);
+ return neg ? -tmp : tmp;
}
EXPORT_SYMBOL_GPL(__ktime_divns);
#endif /* BITS_PER_LONG >= 64 */

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