include/linux/times.h

   1 #ifndef _LINUX_TIMES_H
   2 #define _LINUX_TIMES_H
   3
   4 #ifdef __KERNEL__
   5 #include <linux/timex.h>
   6 #include <asm/div64.h>
   7 #include <asm/types.h>
   8 #include <asm/param.h>
   9
  10 static inline clock_t jiffies_to_clock_t(long x)
  11 {
  12 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
  13         return x / (HZ / USER_HZ);
  14 #else
  15         u64 tmp = (u64)x * TICK_NSEC;
  16         do_div(tmp, (NSEC_PER_SEC / USER_HZ));
  17         return (long)tmp;
  18 #endif
  19 }
  20
  21 static inline unsigned long clock_t_to_jiffies(unsigned long x)
  22 {
  23 #if (HZ % USER_HZ)==0
  24         if (x >= ~0UL / (HZ / USER_HZ))
  25                 return ~0UL;
  26         return x * (HZ / USER_HZ);
  27 #else
  28         u64 jif;
  29
  30         /* Don't worry about loss of precision here .. */
  31         if (x >= ~0UL / HZ * USER_HZ)
  32                 return ~0UL;
  33
  34         /* .. but do try to contain it here */
  35         jif = x * (u64) HZ;
  36         do_div(jif, USER_HZ);
  37         return jif;
  38 #endif
  39 }
  40
  41 static inline u64 jiffies_64_to_clock_t(u64 x)
  42 {
  43 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
  44         do_div(x, HZ / USER_HZ);
  45 #else
  46         /*
  47          * There are better ways that don't overflow early,
  48          * but even this doesn't overflow in hundreds of years
  49          * in 64 bits, so..
  50          */
  51         x *= TICK_NSEC;
  52         do_div(x, (NSEC_PER_SEC / USER_HZ));
  53 #endif
  54         return x;
  55 }
  56 #endif
  57
  58 static inline u64 nsec_to_clock_t(u64 x)
  59 {
  60 #if (NSEC_PER_SEC % USER_HZ) == 0
  61         do_div(x, (NSEC_PER_SEC / USER_HZ));
  62 #elif (USER_HZ % 512) == 0
  63         x *= USER_HZ/512;
  64         do_div(x, (NSEC_PER_SEC / 512));
  65 #else
  66         /*
  67          * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
  68          * overflow after 64.99 years.
  69          * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
  70          */
  71         x *= 9;
  72         do_div(x, (unsigned long)((9ull * NSEC_PER_SEC + (USER_HZ/2))
  73                                   / USER_HZ));
  74 #endif
  75         return x;
  76 }
  77
  78 struct tms {
  79         clock_t tms_utime;
  80         clock_t tms_stime;
  81         clock_t tms_cutime;
  82         clock_t tms_cstime;
  83 };
  84
  85 #endif