src/bin/lttng-sessiond/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 <common/compat/uuid.h>
  33
  34 /* TRACE CLOCK */
  35
  36 struct lttng_trace_clock {
  37         uint64_t (*read64)(void);
  38         uint64_t (*freq)(void);
  39         int (*uuid)(char *uuid);
  40         const char *(*name)(void);
  41         const char *(*description)(void);
  42 };
  43
  44 extern struct lttng_trace_clock *lttng_trace_clock;
  45
  46 void lttng_ust_clock_init(void);
  47
  48 /*
  49  * Currently using the kernel MONOTONIC clock, waiting for kernel-side
  50  * LTTng to implement mmap'd trace clock.
  51  */
  52
  53 /* Choosing correct trace clock */
  54
  55 static __inline__
  56 uint64_t trace_clock_read64_monotonic(void)
  57 {
  58         struct timespec ts;
  59
  60         clock_gettime(CLOCK_MONOTONIC, &ts);
  61         return ((uint64_t) ts.tv_sec * 1000000000ULL) + ts.tv_nsec;
  62 }
  63
  64 static __inline__
  65 uint64_t trace_clock_freq_monotonic(void)
  66 {
  67         return 1000000000ULL;
  68 }
  69
  70 static __inline__
  71 int trace_clock_uuid_monotonic(char *uuid)
  72 {
  73         int ret = 0;
  74         size_t len;
  75         FILE *fp;
  76
  77         /*
  78          * boot_id needs to be read once before being used concurrently
  79          * to deal with a Linux kernel race. A fix is proposed for
  80          * upstream, but the work-around is needed for older kernels.
  81          */
  82         fp = fopen("/proc/sys/kernel/random/boot_id", "r");
  83         if (!fp) {
  84                 return -ENOENT;
  85         }
  86         len = fread(uuid, 1, LTTNG_UST_UUID_STR_LEN - 1, fp);
  87         if (len < LTTNG_UST_UUID_STR_LEN - 1) {
  88                 ret = -EINVAL;
  89                 goto end;
  90         }
  91         uuid[LTTNG_UST_UUID_STR_LEN - 1] = '\0';
  92 end:
  93         fclose(fp);
  94         return ret;
  95 }
  96
  97 static __inline__
  98 const char *trace_clock_name_monotonic(void)
  99 {
 100         return "monotonic";
 101 }
 102
 103 static __inline__
 104 const char *trace_clock_description_monotonic(void)
 105 {
 106         return "Monotonic Clock";
 107 }
 108
 109 static __inline__
 110 uint64_t trace_clock_read64(void)
 111 {
 112         struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
 113
 114         if (caa_likely(!ltc)) {
 115                 return trace_clock_read64_monotonic();
 116         } else {
 117                 cmm_read_barrier_depends();     /* load ltc before content */
 118                 return ltc->read64();
 119         }
 120 }
 121
 122 static __inline__
 123 uint64_t trace_clock_freq(void)
 124 {
 125         struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
 126
 127         if (!ltc) {
 128                 return trace_clock_freq_monotonic();
 129         } else {
 130                 cmm_read_barrier_depends();     /* load ltc before content */
 131                 return ltc->freq();
 132         }
 133 }
 134
 135 static __inline__
 136 int trace_clock_uuid(char *uuid)
 137 {
 138         struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
 139
 140         cmm_read_barrier_depends();     /* load ltc before content */
 141         /* Use default UUID cb when NULL */
 142         if (!ltc || !ltc->uuid) {
 143                 return trace_clock_uuid_monotonic(uuid);
 144         } else {
 145                 return ltc->uuid(uuid);
 146         }
 147 }
 148
 149 static __inline__
 150 const char *trace_clock_name(void)
 151 {
 152         struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
 153
 154         if (!ltc) {
 155                 return trace_clock_name_monotonic();
 156         } else {
 157                 cmm_read_barrier_depends();     /* load ltc before content */
 158                 return ltc->name();
 159         }
 160 }
 161
 162 static __inline__
 163 const char *trace_clock_description(void)
 164 {
 165         struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
 166
 167         if (!ltc) {
 168                 return trace_clock_description_monotonic();
 169         } else {
 170                 cmm_read_barrier_depends();     /* load ltc before content */
 171                 return ltc->description();
 172         }
 173 }
 174
 175 #endif /* _UST_CLOCK_H */