lttng-clock.c

   1 /*
   2  * lttng-clock.c
   3  *
   4  * Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; only
   9  * version 2.1 of the License.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 #include <linux/module.h>
  22 #include <linux/kmod.h>
  23 #include <linux/mutex.h>
  24
  25 #include <wrapper/trace-clock.h>
  26 #include <lttng-events.h>
  27 #include <lttng-tracer.h>
  28
  29 struct lttng_trace_clock *lttng_trace_clock;
  30 EXPORT_SYMBOL_GPL(lttng_trace_clock);
  31
  32 static DEFINE_MUTEX(clock_mutex);
  33 static struct module *lttng_trace_clock_mod;    /* plugin */
  34 static int clock_used;                          /* refcount */
  35
  36 int lttng_clock_register_plugin(struct lttng_trace_clock *ltc,
  37                 struct module *mod)
  38 {
  39         int ret = 0;
  40
  41         mutex_lock(&clock_mutex);
  42         if (clock_used) {
  43                 ret = -EBUSY;
  44                 goto end;
  45         }
  46         if (lttng_trace_clock_mod) {
  47                 ret = -EEXIST;
  48                 goto end;
  49         }
  50         /* set clock */
  51         WRITE_ONCE(lttng_trace_clock, ltc);
  52         lttng_trace_clock_mod = mod;
  53 end:
  54         mutex_unlock(&clock_mutex);
  55         return ret;
  56 }
  57 EXPORT_SYMBOL_GPL(lttng_clock_register_plugin);
  58
  59 void lttng_clock_unregister_plugin(struct lttng_trace_clock *ltc,
  60                 struct module *mod)
  61 {
  62         mutex_lock(&clock_mutex);
  63         WARN_ON_ONCE(clock_used);
  64         if (!lttng_trace_clock_mod) {
  65                 goto end;
  66         }
  67         WARN_ON_ONCE(lttng_trace_clock_mod != mod);
  68
  69         WRITE_ONCE(lttng_trace_clock, NULL);
  70         lttng_trace_clock_mod = NULL;
  71 end:
  72         mutex_unlock(&clock_mutex);
  73 }
  74 EXPORT_SYMBOL_GPL(lttng_clock_unregister_plugin);
  75
  76 void lttng_clock_ref(void)
  77 {
  78         mutex_lock(&clock_mutex);
  79         clock_used++;
  80         if (lttng_trace_clock_mod) {
  81                 int ret;
  82
  83                 ret = try_module_get(lttng_trace_clock_mod);
  84                 if (!ret) {
  85                         printk(KERN_ERR "LTTng-clock cannot get clock plugin module\n");
  86                         WRITE_ONCE(lttng_trace_clock, NULL);
  87                         lttng_trace_clock_mod = NULL;
  88                 }
  89         }
  90         mutex_unlock(&clock_mutex);
  91 }
  92 EXPORT_SYMBOL_GPL(lttng_clock_ref);
  93
  94 void lttng_clock_unref(void)
  95 {
  96         mutex_lock(&clock_mutex);
  97         clock_used--;
  98         if (lttng_trace_clock_mod)
  99                 module_put(lttng_trace_clock_mod);
 100         mutex_unlock(&clock_mutex);
 101 }
 102 EXPORT_SYMBOL_GPL(lttng_clock_unref);
 103
 104 MODULE_LICENSE("GPL and additional rights");
 105 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 106 MODULE_DESCRIPTION("LTTng Clock");
 107 MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
 108         __stringify(LTTNG_MODULES_MINOR_VERSION) "."
 109         __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
 110         LTTNG_MODULES_EXTRAVERSION);