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 <urcu/system.h>
  29 #include <urcu/arch.h>
  30 #include <lttng/ust-clock.h>
  31
  32 #include "lttng-ust-uuid.h"
  33
  34 struct lttng_trace_clock {
  35         uint64_t (*read64)(void);
  36         uint64_t (*freq)(void);
  37         int (*uuid)(char *uuid);
  38         const char *(*name)(void);
  39         const char *(*description)(void);
  40 };
  41
  42 extern struct lttng_trace_clock *lttng_trace_clock;
  43
  44 void lttng_ust_clock_init(void);
  45
  46 /* Use the kernel MONOTONIC clock. */
  47
  48 static __inline__
  49 uint64_t trace_clock_read64_monotonic(void)
  50 {
  51         struct timespec ts;
  52
  53         clock_gettime(CLOCK_MONOTONIC, &ts);
  54         return ((uint64_t) ts.tv_sec * 1000000000ULL) + ts.tv_nsec;
  55 }
  56
  57 static __inline__
  58 uint64_t trace_clock_freq_monotonic(void)
  59 {
  60         return 1000000000ULL;
  61 }
  62
  63 static __inline__
  64 int trace_clock_uuid_monotonic(char *uuid)
  65 {
  66         int ret = 0;
  67         size_t len;
  68         FILE *fp;
  69
  70         /*
  71          * boot_id needs to be read once before being used concurrently
  72          * to deal with a Linux kernel race. A fix is proposed for
  73          * upstream, but the work-around is needed for older kernels.
  74          */
  75         fp = fopen("/proc/sys/kernel/random/boot_id", "r");
  76         if (!fp) {
  77                 return -ENOENT;
  78         }
  79         len = fread(uuid, 1, LTTNG_UST_UUID_STR_LEN - 1, fp);
  80         if (len < LTTNG_UST_UUID_STR_LEN - 1) {
  81                 ret = -EINVAL;
  82                 goto end;
  83         }
  84         uuid[LTTNG_UST_UUID_STR_LEN - 1] = '\0';
  85 end:
  86         fclose(fp);
  87         return ret;
  88 }
  89
  90 static __inline__
  91 const char *trace_clock_name_monotonic(void)
  92 {
  93         return "monotonic";
  94 }
  95
  96 static __inline__
  97 const char *trace_clock_description_monotonic(void)
  98 {
  99         return "Monotonic Clock";
 100 }
 101
 102 static __inline__
 103 uint64_t trace_clock_read64(void)
 104 {
 105         struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
 106
 107         if (caa_likely(!ltc)) {
 108                 return trace_clock_read64_monotonic();
 109         } else {
 110                 cmm_read_barrier_depends();     /* load ltc before content */
 111                 return ltc->read64();
 112         }
 113 }
 114
 115 static __inline__
 116 uint64_t trace_clock_freq(void)
 117 {
 118         struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
 119
 120         if (!ltc) {
 121                 return trace_clock_freq_monotonic();
 122         } else {
 123                 cmm_read_barrier_depends();     /* load ltc before content */
 124                 return ltc->freq();
 125         }
 126 }
 127
 128 static __inline__
 129 int trace_clock_uuid(char *uuid)
 130 {
 131         struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
 132
 133         cmm_read_barrier_depends();     /* load ltc before content */
 134         /* Use default UUID cb when NULL */
 135         if (!ltc || !ltc->uuid) {
 136                 return trace_clock_uuid_monotonic(uuid);
 137         } else {
 138                 return ltc->uuid(uuid);
 139         }
 140 }
 141
 142 static __inline__
 143 const char *trace_clock_name(void)
 144 {
 145         struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
 146
 147         if (!ltc) {
 148                 return trace_clock_name_monotonic();
 149         } else {
 150                 cmm_read_barrier_depends();     /* load ltc before content */
 151                 return ltc->name();
 152         }
 153 }
 154
 155 static __inline__
 156 const char *trace_clock_description(void)
 157 {
 158         struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
 159
 160         if (!ltc) {
 161                 return trace_clock_description_monotonic();
 162         } else {
 163                 cmm_read_barrier_depends();     /* load ltc before content */
 164                 return ltc->description();
 165         }
 166 }
 167
 168 #endif /* _UST_CLOCK_H */