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         if (caa_unlikely(clock_gettime(CLOCK_MONOTONIC, &ts))) {
  54                 ts.tv_sec = 0;
  55                 ts.tv_nsec = 0;
  56         }
  57         return ((uint64_t) ts.tv_sec * 1000000000ULL) + ts.tv_nsec;
  58 }
  59
  60 static __inline__
  61 uint64_t trace_clock_freq_monotonic(void)
  62 {
  63         return 1000000000ULL;
  64 }
  65
  66 static __inline__
  67 int trace_clock_uuid_monotonic(char *uuid)
  68 {
  69         int ret = 0;
  70         size_t len;
  71         FILE *fp;
  72
  73         /*
  74          * boot_id needs to be read once before being used concurrently
  75          * to deal with a Linux kernel race. A fix is proposed for
  76          * upstream, but the work-around is needed for older kernels.
  77          */
  78         fp = fopen("/proc/sys/kernel/random/boot_id", "r");
  79         if (!fp) {
  80                 return -ENOENT;
  81         }
  82         len = fread(uuid, 1, LTTNG_UST_UUID_STR_LEN - 1, fp);
  83         if (len < LTTNG_UST_UUID_STR_LEN - 1) {
  84                 ret = -EINVAL;
  85                 goto end;
  86         }
  87         uuid[LTTNG_UST_UUID_STR_LEN - 1] = '\0';
  88 end:
  89         fclose(fp);
  90         return ret;
  91 }
  92
  93 static __inline__
  94 const char *trace_clock_name_monotonic(void)
  95 {
  96         return "monotonic";
  97 }
  98
  99 static __inline__
 100 const char *trace_clock_description_monotonic(void)
 101 {
 102         return "Monotonic Clock";
 103 }
 104
 105 static __inline__
 106 uint64_t trace_clock_read64(void)
 107 {
 108         struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
 109
 110         if (caa_likely(!ltc)) {
 111                 return trace_clock_read64_monotonic();
 112         } else {
 113                 cmm_read_barrier_depends();     /* load ltc before content */
 114                 return ltc->read64();
 115         }
 116 }
 117
 118 static __inline__
 119 uint64_t trace_clock_freq(void)
 120 {
 121         struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
 122
 123         if (!ltc) {
 124                 return trace_clock_freq_monotonic();
 125         } else {
 126                 cmm_read_barrier_depends();     /* load ltc before content */
 127                 return ltc->freq();
 128         }
 129 }
 130
 131 static __inline__
 132 int trace_clock_uuid(char *uuid)
 133 {
 134         struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
 135
 136         cmm_read_barrier_depends();     /* load ltc before content */
 137         /* Use default UUID cb when NULL */
 138         if (!ltc || !ltc->uuid) {
 139                 return trace_clock_uuid_monotonic(uuid);
 140         } else {
 141                 return ltc->uuid(uuid);
 142         }
 143 }
 144
 145 static __inline__
 146 const char *trace_clock_name(void)
 147 {
 148         struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
 149
 150         if (!ltc) {
 151                 return trace_clock_name_monotonic();
 152         } else {
 153                 cmm_read_barrier_depends();     /* load ltc before content */
 154                 return ltc->name();
 155         }
 156 }
 157
 158 static __inline__
 159 const char *trace_clock_description(void)
 160 {
 161         struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
 162
 163         if (!ltc) {
 164                 return trace_clock_description_monotonic();
 165         } else {
 166                 cmm_read_barrier_depends();     /* load ltc before content */
 167                 return ltc->description();
 168         }
 169 }
 170
 171 #endif /* _UST_CLOCK_H */