src/common/clock.h

   1 /*
   2  * SPDX-License-Identifier: LGPL-2.1-only
   3  *
   4  * Copyright (C) 2016 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  */
   6
   7 #ifndef _UST_COMMON_CLOCK_H
   8 #define _UST_COMMON_CLOCK_H
   9
  10 #include <time.h>
  11 #include <sys/time.h>
  12 #include <stdint.h>
  13 #include <stddef.h>
  14 #include <stdio.h>
  15
  16 #include <urcu/system.h>
  17 #include <urcu/arch.h>
  18 #include <lttng/ust-clock.h>
  19
  20 struct lttng_ust_trace_clock {
  21         uint64_t (*read64)(void);
  22         uint64_t (*freq)(void);
  23         int (*uuid)(char *uuid);
  24         const char *(*name)(void);
  25         const char *(*description)(void);
  26 };
  27
  28 /*
  29  * The trace clock is a public symbol of liblttng-ust-common accessed by other
  30  * libraries through the trace_clock_read64 static inline function. It is
  31  * initialised in the liblttng-ust-common constructor.
  32  */
  33 extern struct lttng_ust_trace_clock *lttng_ust_trace_clock;
  34
  35 /* Use the kernel MONOTONIC clock. */
  36
  37 static __inline__
  38 uint64_t trace_clock_read64_monotonic(void)
  39 {
  40         struct timespec ts;
  41
  42         if (caa_unlikely(clock_gettime(CLOCK_MONOTONIC, &ts))) {
  43                 ts.tv_sec = 0;
  44                 ts.tv_nsec = 0;
  45         }
  46         return ((uint64_t) ts.tv_sec * 1000000000ULL) + ts.tv_nsec;
  47 }
  48
  49 static __inline__
  50 uint64_t trace_clock_read64(void)
  51 {
  52         struct lttng_ust_trace_clock *ltc = CMM_LOAD_SHARED(lttng_ust_trace_clock);
  53
  54         if (caa_likely(!ltc)) {
  55                 return trace_clock_read64_monotonic();
  56         } else {
  57                 cmm_read_barrier_depends();     /* load ltc before content */
  58                 return ltc->read64();
  59         }
  60 }
  61
  62 #endif  /* _UST_COMMON_CLOCK_H */