Fix: check reference counts for overflow

[lttng-modules.git] / wrapper / kref.h

diff --git a/wrapper/kref.h b/wrapper/kref.h
new file mode 100644 (file)
index 0000000..eedefbf
--- /dev/null
+++ b/wrapper/kref.h
@@ -0,0 +1,46 @@
+#ifndef _LTTNG_WRAPPER_KREF_H
+#define _LTTNG_WRAPPER_KREF_H
+
+/*
+ * wrapper/kref.h
+ *
+ * wrapper around linux/kref.h.
+ *
+ * Copyright (C) 2016 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; only version 2 of the License.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * This wrapper code is derived from Linux 3.19.2 include/linux/list.h
+ * and include/linux/rculist.h, hence the GPLv2 license applied to this
+ * file.
+ */
+
+#include <linux/kref.h>
+#include <linux/rculist.h>
+
+/*
+ * lttng_kref_get: get reference count, checking for overflow.
+ *
+ * Return 1 if reference is taken, 0 otherwise (overflow).
+ */
+static inline int lttng_kref_get(struct kref *kref)
+{
+       if (atomic_add_unless(&kref->refcount, 1, INT_MAX) != INT_MAX) {
+               return 1;
+       } else {
+               return 0;
+       }
+}
+
+#endif /* _LTTNG_WRAPPER_KREF_H */