include/wrapper/kref.h

   1 /* SPDX-License-Identifier: GPL-2.0-only
   2  *
   3  * wrapper/kref.h
   4  *
   5  * wrapper around linux/kref.h.
   6  *
   7  * Copyright (C) 2016 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *
   9  * This wrapper code is derived from Linux 3.19.2 include/linux/list.h
  10  * and include/linux/rculist.h, hence the GPLv2 license applied to this
  11  * file.
  12  */
  13
  14 #ifndef _LTTNG_WRAPPER_KREF_H
  15 #define _LTTNG_WRAPPER_KREF_H
  16
  17 #include <linux/kref.h>
  18 #include <linux/rculist.h>
  19 #include <linux/version.h>
  20
  21 /*
  22  * lttng_kref_get: get reference count, checking for overflow.
  23  *
  24  * Return 1 if reference is taken, 0 otherwise (overflow).
  25  */
  26 #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,11,0))
  27 static inline int lttng_kref_get(struct kref *kref)
  28 {
  29         kref_get(kref);
  30         return 1;
  31 }
  32 #else /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,11,0)) */
  33 static inline int lttng_kref_get(struct kref *kref)
  34 {
  35         return atomic_add_unless(&kref->refcount, 1, INT_MAX);
  36 }
  37 #endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,11,0)) */
  38
  39 #endif /* _LTTNG_WRAPPER_KREF_H */