clock override: use getter API from LTTng-UST
authorMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Tue, 23 Mar 2021 16:01:43 +0000 (12:01 -0400)
committerJérémie Galarneau <jeremie.galarneau@efficios.com>
Tue, 23 Mar 2021 19:44:35 +0000 (15:44 -0400)
Currently, the lttng session daemon reimplements its own copy of
struct lttng_trace_clock, which is pretty bad as ABI go.

Use getter functions for each of the clock callback instead. This
refactoring needs to be introduced with a matching commit to implement
the new ABI in LTTng-UST.

Move the implementation of the clock frequency, uuid, name and
description default callbacks (for monotonic clock) to lttng-ust.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: If2e671bacacc55d3fb27b6b4d4fc8c16aaffd059

src/bin/lttng-sessiond/ust-clock.h

index ee53a99a173b6bafc0556913b871127fd4d936ce..91cbbe62862261401038776da5297557f1dfe130 100644 (file)
 
 #include <common/uuid.h>
 
-/* 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);
-
-/*
- * Currently using the kernel MONOTONIC clock, waiting for kernel-side
- * LTTng to implement mmap'd trace clock.
- */
-
-/* Choosing correct trace clock */
-
 static __inline__
-uint64_t trace_clock_read64_monotonic(void)
+uint64_t trace_clock_read64(void)
 {
-       struct timespec ts;
+       uint64_t clock_value = 0;
+       lttng_ust_clock_read64_function read64_cb;
 
-       if (lttng_clock_gettime(CLOCK_MONOTONIC, &ts)) {
-               /* TODO Report error cleanly up the chain. */
-               PERROR("clock_gettime CLOCK_MONOTONIC");
-               ts.tv_sec = 0;
-               ts.tv_nsec = 0;
+       if (lttng_ust_trace_clock_get_read64_cb(&read64_cb)) {
+               goto end;
        }
-       return ((uint64_t) ts.tv_sec * 1000000000ULL) + ts.tv_nsec;
-}
 
-static __inline__
-uint64_t trace_clock_freq_monotonic(void)
-{
-       return 1000000000ULL;
+       clock_value = read64_cb();
+end:
+       return clock_value;
 }
 
 static __inline__
-int trace_clock_uuid_monotonic(char *uuid)
+uint64_t trace_clock_freq(void)
 {
-       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;
+       uint64_t frequency = 0;
+       lttng_ust_clock_freq_function get_freq_cb;
+
+       if (lttng_ust_trace_clock_get_freq_cb(&get_freq_cb)) {
                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";
-}
 
-static __inline__
-const char *trace_clock_description_monotonic(void)
-{
-       return "Monotonic Clock";
+       frequency = get_freq_cb();
+end:
+       return frequency;
 }
 
 static __inline__
-uint64_t trace_clock_read64(void)
+int trace_clock_uuid(char *uuid)
 {
-       struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
+       int ret;
+       lttng_ust_clock_uuid_function get_uuid_cb;
 
-       if (caa_likely(!ltc)) {
-               return trace_clock_read64_monotonic();
-       } else {
-               cmm_read_barrier_depends();     /* load ltc before content */
-               return ltc->read64();
+       if (lttng_ust_trace_clock_get_uuid_cb(&get_uuid_cb)) {
+               ret = -EINVAL;
+               goto end;
        }
-}
 
-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();
-       }
-}
+       ret = get_uuid_cb(uuid);
+end:
+       return ret;
 
-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);
+       const char *name;
+       lttng_ust_clock_name_function get_name_cb;
 
-       if (!ltc) {
-               return trace_clock_name_monotonic();
-       } else {
-               cmm_read_barrier_depends();     /* load ltc before content */
-               return ltc->name();
+       if (lttng_ust_trace_clock_get_name_cb(&get_name_cb)) {
+               name = NULL;
+               goto end;
        }
+
+       name = get_name_cb();
+end:
+       return name;
 }
 
 static __inline__
 const char *trace_clock_description(void)
 {
-       struct lttng_trace_clock *ltc = CMM_LOAD_SHARED(lttng_trace_clock);
+       const char *description;
+       lttng_ust_clock_description_function get_description_cb;
 
-       if (!ltc) {
-               return trace_clock_description_monotonic();
-       } else {
-               cmm_read_barrier_depends();     /* load ltc before content */
-               return ltc->description();
+       if (lttng_ust_trace_clock_get_description_cb(&get_description_cb)) {
+               description = NULL;
+               goto end;
        }
+
+       description = get_description_cb();
+end:
+       return description;
 }
 
 #endif /* _UST_CLOCK_H */
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