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 <common/compat/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/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         if (lttng_clock_gettime(CLOCK_MONOTONIC, &ts)) {
  61                 /* TODO Report error cleanly up the chain. */
  62                 PERROR("clock_gettime CLOCK_MONOTONIC");
  63                 ts.tv_sec = 0;
  64                 ts.tv_nsec = 0;
  65         }
  66         return ((uint64_t) ts.tv_sec * 1000000000ULL) + ts.tv_nsec;
  67 }
  68
  69 static __inline__
  70 uint64_t trace_clock_freq_monotonic(void)
  71 {
  72         return 1000000000ULL;
  73 }
  74
  75 static __inline__
  76 int trace_clock_uuid_monotonic(char *uuid)
  77 {
  78         int ret = 0;
  79         size_t len;
  80         FILE *fp;
  81
  82         /*
  83          * boot_id needs to be read once before being used concurrently
  84          * to deal with a Linux kernel race. A fix is proposed for
  85          * upstream, but the work-around is needed for older kernels.
  86          */
  87         fp = fopen("/proc/sys/kernel/random/boot_id", "r");
  88         if (!fp) {
  89                 return -ENOENT;
  90         }
  91         len = fread(uuid, 1, LTTNG_UST_UUID_STR_LEN - 1, fp);
  92         if (len < LTTNG_UST_UUID_STR_LEN - 1) {
  93                 ret = -EINVAL;
  94                 goto end;
  95         }
  96         uuid[LTTNG_UST_UUID_STR_LEN - 1] = '\0';
  97 end:
  98         fclose(fp);
  99         return ret;
 100 }
 101
 102 static __inline__
 103 const char *trace_clock_name_monotonic(void)
 104 {
 105         return "monotonic";
 106 }
 107
 108 static __inline__
 109 const char *trace_clock_description_monotonic(void)
 110 {
 111         return "Monotonic Clock";
 112 }
 113
 114 static __inline__
 115 uint64_t trace_clock_read64(void)
 116 {
 117         struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
 118
 119         if (caa_likely(!ltc)) {
 120                 return trace_clock_read64_monotonic();
 121         } else {
 122                 cmm_read_barrier_depends();     /* load ltc before content */
 123                 return ltc->read64();
 124         }
 125 }
 126
 127 static __inline__
 128 uint64_t trace_clock_freq(void)
 129 {
 130         struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
 131
 132         if (!ltc) {
 133                 return trace_clock_freq_monotonic();
 134         } else {
 135                 cmm_read_barrier_depends();     /* load ltc before content */
 136                 return ltc->freq();
 137         }
 138 }
 139
 140 static __inline__
 141 int trace_clock_uuid(char *uuid)
 142 {
 143         struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
 144
 145         cmm_read_barrier_depends();     /* load ltc before content */
 146         /* Use default UUID cb when NULL */
 147         if (!ltc || !ltc->uuid) {
 148                 return trace_clock_uuid_monotonic(uuid);
 149         } else {
 150                 return ltc->uuid(uuid);
 151         }
 152 }
 153
 154 static __inline__
 155 const char *trace_clock_name(void)
 156 {
 157         struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
 158
 159         if (!ltc) {
 160                 return trace_clock_name_monotonic();
 161         } else {
 162                 cmm_read_barrier_depends();     /* load ltc before content */
 163                 return ltc->name();
 164         }
 165 }
 166
 167 static __inline__
 168 const char *trace_clock_description(void)
 169 {
 170         struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
 171
 172         if (!ltc) {
 173                 return trace_clock_description_monotonic();
 174         } else {
 175                 cmm_read_barrier_depends();     /* load ltc before content */
 176                 return ltc->description();
 177         }
 178 }
 179
 180 #endif /* _UST_CLOCK_H */