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 #include "uuid.h"
  29
  30 /* TRACE CLOCK */
  31
  32 /*
  33  * Currently using the kernel MONOTONIC clock, waiting for kernel-side
  34  * LTTng to implement mmap'd trace clock.
  35  */
  36
  37 /* Choosing correct trace clock */
  38
  39 static __inline__
  40 uint64_t trace_clock_read64(void)
  41 {
  42         struct timespec ts;
  43
  44         clock_gettime(CLOCK_MONOTONIC, &ts);
  45         return ((uint64_t) ts.tv_sec * 1000000000ULL) + ts.tv_nsec;
  46 }
  47
  48 static __inline__
  49 uint64_t trace_clock_freq(void)
  50 {
  51         return 1000000000ULL;
  52 }
  53
  54 static __inline__
  55 const int trace_clock_uuid(char *uuid)
  56 {
  57         int ret = 0;
  58         size_t len;
  59         FILE *fp;
  60
  61         /*
  62          * boot_id needs to be read once before being used concurrently
  63          * to deal with a Linux kernel race. A fix is proposed for
  64          * upstream, but the work-around is needed for older kernels.
  65          */
  66         fp = fopen("/proc/sys/kernel/random/boot_id", "r");
  67         if (!fp) {
  68                 return -ENOENT;
  69         }
  70         len = fread(uuid, 1, LTTNG_UST_UUID_STR_LEN - 1, fp);
  71         if (len < LTTNG_UST_UUID_STR_LEN - 1) {
  72                 ret = -EINVAL;
  73                 goto end;
  74         }
  75         uuid[LTTNG_UST_UUID_STR_LEN - 1] = '\0';
  76 end:
  77         fclose(fp);
  78         return ret;
  79 }
  80
  81 #endif /* _UST_CLOCK_H */