Implement clock plugin support

[lttng-modules.git] / lttng-clock.c

diff --git a/lttng-clock.c b/lttng-clock.c
new file mode 100644 (file)
index 0000000..4296d6c
--- /dev/null
+++ b/lttng-clock.c
@@ -0,0 +1,110 @@
+/*
+ * lttng-clock.c
+ *
+ * Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; only
+ * version 2.1 of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <linux/module.h>
+#include <linux/kmod.h>
+#include <linux/mutex.h>
+
+#include "wrapper/trace-clock.h"
+#include "lttng-events.h"
+#include "lttng-tracer.h"
+
+struct lttng_trace_clock *lttng_trace_clock;
+EXPORT_SYMBOL_GPL(lttng_trace_clock);
+
+static DEFINE_MUTEX(clock_mutex);
+static struct module *lttng_trace_clock_mod;   /* plugin */
+static int clock_used;                         /* refcount */
+
+int lttng_clock_register_plugin(struct lttng_trace_clock *ltc,
+               struct module *mod)
+{
+       int ret = 0;
+
+       mutex_lock(&clock_mutex);
+       if (clock_used) {
+               ret = -EBUSY;
+               goto end;
+       }
+       if (lttng_trace_clock_mod) {
+               ret = -EEXIST;
+               goto end;
+       }
+       /* set clock */
+       ACCESS_ONCE(lttng_trace_clock) = ltc;
+       lttng_trace_clock_mod = mod;
+end:
+       mutex_unlock(&clock_mutex);
+       return ret;
+}
+EXPORT_SYMBOL_GPL(lttng_clock_register_plugin);
+
+void lttng_clock_unregister_plugin(struct lttng_trace_clock *ltc,
+               struct module *mod)
+{
+       mutex_lock(&clock_mutex);
+       WARN_ON_ONCE(clock_used);
+       if (!lttng_trace_clock_mod) {
+               goto end;
+       }
+       WARN_ON_ONCE(lttng_trace_clock_mod != mod);
+
+       ACCESS_ONCE(lttng_trace_clock) = NULL;
+       lttng_trace_clock_mod = NULL;
+end:
+       mutex_unlock(&clock_mutex);
+}
+EXPORT_SYMBOL_GPL(lttng_clock_unregister_plugin);
+
+void lttng_clock_ref(void)
+{
+       mutex_lock(&clock_mutex);
+       clock_used++;
+       if (lttng_trace_clock_mod) {
+               int ret;
+
+               ret = try_module_get(lttng_trace_clock_mod);
+               if (!ret) {
+                       printk(KERN_ERR "LTTng-clock cannot get clock plugin module\n");
+                       ACCESS_ONCE(lttng_trace_clock) = NULL;
+                       lttng_trace_clock_mod = NULL;
+               }
+       }
+       mutex_unlock(&clock_mutex);
+}
+EXPORT_SYMBOL_GPL(lttng_clock_ref);
+
+void lttng_clock_unref(void)
+{
+       mutex_lock(&clock_mutex);
+       clock_used--;
+       if (lttng_trace_clock_mod)
+               module_put(lttng_trace_clock_mod);
+       mutex_unlock(&clock_mutex);
+}
+EXPORT_SYMBOL_GPL(lttng_clock_unref);
+
+MODULE_LICENSE("GPL and additional rights");
+MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
+MODULE_DESCRIPTION("LTTng Clock");
+MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
+       __stringify(LTTNG_MODULES_MINOR_VERSION) "."
+       __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
+       LTTNG_MODULES_EXTRAVERSION);