LXR linux/tools/perf/arch/x86/util/tsc.c

   1#include <stdbool.h>
   2#include <errno.h>
   3
   4#include <linux/perf_event.h>
   5
   6#include "../../perf.h"
   7#include <linux/types.h>
   8#include "../../util/debug.h"
   9#include "../../util/tsc.h"
  10#include "tsc.h"
  11
  12int perf_read_tsc_conversion(const struct perf_event_mmap_page *pc,
  13                             struct perf_tsc_conversion *tc)
  14{
  15        bool cap_user_time_zero;
  16        u32 seq;
  17        int i = 0;
  18
  19        while (1) {
  20                seq = pc->lock;
  21                rmb();
  22                tc->time_mult = pc->time_mult;
  23                tc->time_shift = pc->time_shift;
  24                tc->time_zero = pc->time_zero;
  25                cap_user_time_zero = pc->cap_user_time_zero;
  26                rmb();
  27                if (pc->lock == seq && !(seq & 1))
  28                        break;
  29                if (++i > 10000) {
  30                        pr_debug("failed to get perf_event_mmap_page lock\n");
  31                        return -EINVAL;
  32                }
  33        }
  34
  35        if (!cap_user_time_zero)
  36                return -EOPNOTSUPP;
  37
  38        return 0;
  39}
  40
  41u64 rdtsc(void)
  42{
  43        unsigned int low, high;
  44
  45        asm volatile("rdtsc" : "=a" (low), "=d" (high));
  46
  47        return low | ((u64)high) << 32;
  48}
  49