lttng-ust(3): specify "If set" instead of "if set to 1" for some variables

[lttng-ust.git] / liblttng-ust / clock.h

diff --git a/liblttng-ust/clock.h b/liblttng-ust/clock.h
index ed191b0bf9b7ca4b75a55ddbb17682e052b0ad4c..a7e8eb7b49e062b1e5ebe9f24cd7d60278a4c64e 100644 (file)
--- a/liblttng-ust/clock.h
+++ b/liblttng-ust/clock.h
@@ -24,34 +24,148 @@
 #include <sys/time.h>
 #include <stdint.h>
 #include <stddef.h>
+#include <stdio.h>
+#include <urcu/system.h>
+#include <urcu/arch.h>
+#include <lttng/ust-clock.h>
 
-/* TRACE CLOCK */
+#include "lttng-ust-uuid.h"
 
-/*
- * Currently using the kernel MONOTONIC clock, waiting for kernel-side
- * LTTng to implement mmap'd trace clock.
- */
+struct lttng_trace_clock {
+       uint64_t (*read64)(void);
+       uint64_t (*freq)(void);
+       int (*uuid)(char *uuid);
+       const char *(*name)(void);
+       const char *(*description)(void);
+};
+
+extern struct lttng_trace_clock *lttng_trace_clock;
+
+void lttng_ust_clock_init(void);
 
-/* Choosing correct trace clock */
+/* Use the kernel MONOTONIC clock. */
 
-static __inline__ uint64_t trace_clock_read64(void)
+static __inline__
+uint64_t trace_clock_read64_monotonic(void)
 {
        struct timespec ts;
 
-       clock_gettime(CLOCK_MONOTONIC, &ts);
-       return (ts.tv_sec * 1000000000) + ts.tv_nsec;
+       if (caa_unlikely(clock_gettime(CLOCK_MONOTONIC, &ts))) {
+               ts.tv_sec = 0;
+               ts.tv_nsec = 0;
+       }
+       return ((uint64_t) ts.tv_sec * 1000000000ULL) + ts.tv_nsec;
+}
+
+static __inline__
+uint64_t trace_clock_freq_monotonic(void)
+{
+       return 1000000000ULL;
+}
+
+static __inline__
+int trace_clock_uuid_monotonic(char *uuid)
+{
+       int ret = 0;
+       size_t len;
+       FILE *fp;
+
+       /*
+        * boot_id needs to be read once before being used concurrently
+        * to deal with a Linux kernel race. A fix is proposed for
+        * upstream, but the work-around is needed for older kernels.
+        */
+       fp = fopen("/proc/sys/kernel/random/boot_id", "r");
+       if (!fp) {
+               return -ENOENT;
+       }
+       len = fread(uuid, 1, LTTNG_UST_UUID_STR_LEN - 1, fp);
+       if (len < LTTNG_UST_UUID_STR_LEN - 1) {
+               ret = -EINVAL;
+               goto end;
+       }
+       uuid[LTTNG_UST_UUID_STR_LEN - 1] = '\0';
+end:
+       fclose(fp);
+       return ret;
+}
+
+static __inline__
+const char *trace_clock_name_monotonic(void)
+{
+       return "monotonic";
 }
 
-#if __i386__ || __x86_64__
-static __inline__ uint64_t trace_clock_frequency(void)
+static __inline__
+const char *trace_clock_description_monotonic(void)
 {
-       return 1000000000LL;
+       return "Monotonic Clock";
 }
-#endif /* #else #if __i386__ || __x86_64__ */
 
-static __inline__ uint32_t trace_clock_freq_scale(void)
+static __inline__
+uint64_t trace_clock_read64(void)
 {
-       return 1;
+       struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
+
+       if (caa_likely(!ltc)) {
+               return trace_clock_read64_monotonic();
+       } else {
+               cmm_read_barrier_depends();     /* load ltc before content */
+               return ltc->read64();
+       }
+}
+
+static __inline__
+uint64_t trace_clock_freq(void)
+{
+       struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
+
+       if (!ltc) {
+               return trace_clock_freq_monotonic();
+       } else {
+               cmm_read_barrier_depends();     /* load ltc before content */
+               return ltc->freq();
+       }
+}
+
+static __inline__
+int trace_clock_uuid(char *uuid)
+{
+       struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
+
+       cmm_read_barrier_depends();     /* load ltc before content */
+       /* Use default UUID cb when NULL */
+       if (!ltc || !ltc->uuid) {
+               return trace_clock_uuid_monotonic(uuid);
+       } else {
+               return ltc->uuid(uuid);
+       }
+}
+
+static __inline__
+const char *trace_clock_name(void)
+{
+       struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
+
+       if (!ltc) {
+               return trace_clock_name_monotonic();
+       } else {
+               cmm_read_barrier_depends();     /* load ltc before content */
+               return ltc->name();
+       }
+}
+
+static __inline__
+const char *trace_clock_description(void)
+{
+       struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
+
+       if (!ltc) {
+               return trace_clock_description_monotonic();
+       } else {
+               cmm_read_barrier_depends();     /* load ltc before content */
+               return ltc->description();
+       }
 }
 
 #endif /* _UST_CLOCK_H */