--- /dev/null
+/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
+ *
+ * lttng-clock.c
+ *
+ * Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ */
+
+#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 */
+ WRITE_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);
+
+ WRITE_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");
+ WRITE_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);