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