src/lttng-clock.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-clock.c
   4  *
   5  * Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   6  */
   7
   8 #include <linux/module.h>
   9 #include <linux/kmod.h>
  10 #include <linux/mutex.h>
  11
  12 #include <wrapper/trace-clock.h>
  13 #include <lttng/events.h>
  14 #include <lttng/tracer.h>
  15 #include <lttng/events-internal.h>
  16
  17 struct lttng_trace_clock *lttng_trace_clock;
  18 EXPORT_SYMBOL_GPL(lttng_trace_clock);
  19
  20 static DEFINE_MUTEX(clock_mutex);
  21 static struct module *lttng_trace_clock_mod;    /* plugin */
  22 static int clock_used;                          /* refcount */
  23
  24 int lttng_clock_register_plugin(struct lttng_trace_clock *ltc,
  25                 struct module *mod)
  26 {
  27         int ret = 0;
  28
  29         mutex_lock(&clock_mutex);
  30         if (clock_used) {
  31                 ret = -EBUSY;
  32                 goto end;
  33         }
  34         if (lttng_trace_clock_mod) {
  35                 ret = -EEXIST;
  36                 goto end;
  37         }
  38         /* set clock */
  39         WRITE_ONCE(lttng_trace_clock, ltc);
  40         lttng_trace_clock_mod = mod;
  41 end:
  42         mutex_unlock(&clock_mutex);
  43         return ret;
  44 }
  45 EXPORT_SYMBOL_GPL(lttng_clock_register_plugin);
  46
  47 void lttng_clock_unregister_plugin(struct lttng_trace_clock *ltc,
  48                 struct module *mod)
  49 {
  50         mutex_lock(&clock_mutex);
  51         WARN_ON_ONCE(clock_used);
  52         if (!lttng_trace_clock_mod) {
  53                 goto end;
  54         }
  55         WARN_ON_ONCE(lttng_trace_clock_mod != mod);
  56
  57         WRITE_ONCE(lttng_trace_clock, NULL);
  58         lttng_trace_clock_mod = NULL;
  59 end:
  60         mutex_unlock(&clock_mutex);
  61 }
  62 EXPORT_SYMBOL_GPL(lttng_clock_unregister_plugin);
  63
  64 void lttng_clock_ref(void)
  65 {
  66         mutex_lock(&clock_mutex);
  67         clock_used++;
  68         if (lttng_trace_clock_mod) {
  69                 int ret;
  70
  71                 ret = try_module_get(lttng_trace_clock_mod);
  72                 if (!ret) {
  73                         printk(KERN_ERR "LTTng: LTTng-clock cannot get clock plugin module\n");
  74                         WRITE_ONCE(lttng_trace_clock, NULL);
  75                         lttng_trace_clock_mod = NULL;
  76                 }
  77         }
  78         mutex_unlock(&clock_mutex);
  79 }
  80 EXPORT_SYMBOL_GPL(lttng_clock_ref);
  81
  82 void lttng_clock_unref(void)
  83 {
  84         mutex_lock(&clock_mutex);
  85         clock_used--;
  86         if (lttng_trace_clock_mod)
  87                 module_put(lttng_trace_clock_mod);
  88         mutex_unlock(&clock_mutex);
  89 }
  90 EXPORT_SYMBOL_GPL(lttng_clock_unref);
  91
  92 MODULE_LICENSE("GPL and additional rights");
  93 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
  94 MODULE_DESCRIPTION("LTTng Clock");
  95 MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
  96         __stringify(LTTNG_MODULES_MINOR_VERSION) "."
  97         __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
  98         LTTNG_MODULES_EXTRAVERSION);