diff options
| -rw-r--r-- | include/linux/jiffies.h | 1 | ||||
| -rw-r--r-- | kernel/sched.c | 3 | ||||
| -rw-r--r-- | kernel/time.c | 30 |
3 files changed, 32 insertions, 2 deletions
diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h index 1a9cf78bfce..6811f4bfc6e 100644 --- a/include/linux/jiffies.h +++ b/include/linux/jiffies.h @@ -307,6 +307,7 @@ extern clock_t jiffies_to_clock_t(long x); extern unsigned long clock_t_to_jiffies(unsigned long x); extern u64 jiffies_64_to_clock_t(u64 x); extern u64 nsec_to_clock_t(u64 x); +extern unsigned long nsecs_to_jiffies(u64 n); #define TIMESTAMP_SIZE 30 diff --git a/kernel/sched.c b/kernel/sched.c index 82251c21f78..b3d4e2be95a 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -5192,8 +5192,7 @@ void task_times(struct task_struct *p, cputime_t *ut, cputime_t *st) #else #ifndef nsecs_to_cputime -# define nsecs_to_cputime(__nsecs) \ - msecs_to_cputime(div_u64((__nsecs), NSEC_PER_MSEC)) +# define nsecs_to_cputime(__nsecs) nsecs_to_jiffies(__nsecs) #endif void task_times(struct task_struct *p, cputime_t *ut, cputime_t *st) diff --git a/kernel/time.c b/kernel/time.c index 2e2e469a7fe..804798005d1 100644 --- a/kernel/time.c +++ b/kernel/time.c @@ -662,6 +662,36 @@ u64 nsec_to_clock_t(u64 x) #endif } +/** + * nsecs_to_jiffies - Convert nsecs in u64 to jiffies + * + * @n: nsecs in u64 + * + * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64. + * And this doesn't return MAX_JIFFY_OFFSET since this function is designed + * for scheduler, not for use in device drivers to calculate timeout value. + * + * note: + * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512) + * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years + */ +unsigned long nsecs_to_jiffies(u64 n) +{ +#if (NSEC_PER_SEC % HZ) == 0 + /* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */ + return div_u64(n, NSEC_PER_SEC / HZ); +#elif (HZ % 512) == 0 + /* overflow after 292 years if HZ = 1024 */ + return div_u64(n * HZ / 512, NSEC_PER_SEC / 512); +#else + /* + * Generic case - optimized for cases where HZ is a multiple of 3. + * overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc. + */ + return div_u64(n * 9, (9ull * NSEC_PER_SEC + HZ / 2) / HZ); +#endif +} + #if (BITS_PER_LONG < 64) u64 get_jiffies_64(void) { |