liblttng-ust/clock.h

   1 /*
   2  * Copyright (C) 2010  Pierre-Marc Fournier
   3  * Copyright (C) 2011  Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; version 2.1 of
   8  * the License.
   9  *
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General Public
  16  * License along with this library; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
  18  */
  19
  20 #ifndef _UST_CLOCK_H
  21 #define _UST_CLOCK_H
  22
  23 #include <time.h>
  24 #include <sys/time.h>
  25 #include <stdint.h>
  26 #include <stddef.h>
  27 #include <stdio.h>
  28
  29 /*
  30  * Includes final \0.
  31  */
  32 #define CLOCK_UUID_LEN          37
  33
  34 /* TRACE CLOCK */
  35
  36 /*
  37  * Currently using the kernel MONOTONIC clock, waiting for kernel-side
  38  * LTTng to implement mmap'd trace clock.
  39  */
  40
  41 /* Choosing correct trace clock */
  42
  43 static __inline__
  44 uint64_t trace_clock_read64(void)
  45 {
  46         struct timespec ts;
  47
  48         clock_gettime(CLOCK_MONOTONIC, &ts);
  49         return ((uint64_t) ts.tv_sec * 1000000000ULL) + ts.tv_nsec;
  50 }
  51
  52 static __inline__
  53 uint64_t trace_clock_freq(void)
  54 {
  55         return 1000000000ULL;
  56 }
  57
  58 static __inline__
  59 const int trace_clock_uuid(char *uuid)
  60 {
  61         int ret = 0;
  62         size_t len;
  63         FILE *fp;
  64
  65         /*
  66          * boot_id needs to be read once before being used concurrently
  67          * to deal with a Linux kernel race. A fix is proposed for
  68          * upstream, but the work-around is needed for older kernels.
  69          */
  70         fp = fopen("/proc/sys/kernel/random/boot_id", "r");
  71         if (!fp) {
  72                 return -ENOENT;
  73         }
  74         len = fread(uuid, 1, CLOCK_UUID_LEN - 1, fp);
  75         if (len < CLOCK_UUID_LEN - 1) {
  76                 ret = -EINVAL;
  77                 goto end;
  78         }
  79         uuid[CLOCK_UUID_LEN - 1] = '\0';
  80 end:
  81         fclose(fp);
  82         return ret;
  83 }
  84
  85 #endif /* _UST_CLOCK_H */