urcu-pointer: create specific objects and headers to deal with RCU pointers

[urcu.git] / urcu-pointer.h

diff --git a/urcu-pointer.h b/urcu-pointer.h
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+#ifndef _URCU_POINTER_H
+#define _URCU_POINTER_H
+
+/*
+ * urcu-pointer.h
+ *
+ * Userspace RCU header. Operations on pointers.
+ *
+ * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+ * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
+ *
+ * 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; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * 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
+ *
+ * IBM's contributions to this file may be relicensed under LGPLv2 or later.
+ */
+
+#include <urcu/compiler.h>
+#include <urcu/arch.h>
+#include <urcu/arch_uatomic.h>
+
+#ifdef _LGPL_SOURCE
+
+#include <urcu-pointer-static.h>
+
+/*
+ * rcu_dereference(ptr)
+ *
+ * Fetch a RCU-protected pointer. Typically used to copy the variable ptr to a
+ * local variable.
+ */
+#define rcu_dereference                _rcu_dereference
+
+/*
+ * rcu_cmpxchg_pointer(type **ptr, type *new, type *old)
+ * type *rcu_xchg_pointer(type **ptr, type *new)
+ * type *rcu_set_pointer(type **ptr, type *new)
+ *
+ * RCU pointer updates.
+ * @ptr: address of the pointer to modify
+ * @new: new pointer value
+ * @old: old pointer value (expected)
+ *
+ * return: old pointer value
+ */
+#define rcu_cmpxchg_pointer    _rcu_cmpxchg_pointer
+#define rcu_xchg_pointer       _rcu_xchg_pointer
+#define rcu_set_pointer                _rcu_set_pointer
+
+/*
+ * type *rcu_publish_content(type **ptr, type *new)
+ *
+ * Exchanges the pointer and waits for quiescent state. The pointer returned
+ * can be freed. You are encouraged to use either
+ * - rcu_cmpxchg_pointer
+ * - rcu_xchg_pointer
+ * - rcu_set_pointer
+ * with call_rcu(free, ptr) instead to deal with reclamation more efficiently.
+ */
+#define rcu_publish_content    _rcu_publish_content
+
+#else /* !_LGPL_SOURCE */
+
+extern void *rcu_dereference(void *p);
+
+extern void *rcu_cmpxchg_pointer_sym(void **p, void *old, void *_new);
+#define rcu_cmpxchg_pointer(p, old, _new)              \
+       rcu_cmpxchg_pointer_sym((void **)(p), (old), (_new))
+
+extern void *rcu_xchg_pointer_sym(void **p, void *v);
+#define rcu_xchg_pointer(p, v)                         \
+       rcu_xchg_pointer_sym((void **)(p), (v))
+
+extern void *rcu_set_pointer_sym(void **p, void *v);
+#define rcu_set_pointer(p, v)                          \
+       rcu_set_pointer_sym((void **)(p), (v))
+
+extern void *rcu_publish_content_sym(void **p, void *v);
+#define rcu_publish_content(p, v)                      \
+       rcu_publish_content_sym((void **)(p), (v))
+
+extern void *rcu_assign_pointer_sym(void **p, void *v);
+
+#endif /* !_LGPL_SOURCE */
+
+/*
+ * rcu_assign_pointer(type *ptr, type *new)
+ *
+ * Same as rcu_set_pointer, but takes the pointer to assign to rather than its
+ * address as first parameter. Provided for compatibility with the Linux kernel
+ * RCU semantic.
+ */
+#define rcu_assign_pointer(p, v)       rcu_set_pointer((&p), (v))
+
+#endif /* _URCU_POINTER_H */