[urcu.git] / urcu-pointer-static.h

#ifndef _URCU_POINTER_STATIC_H
#define _URCU_POINTER_STATIC_H

/*
 * urcu-pointer-static.h
 *
 * Userspace RCU header. Operations on pointers.
 *
 * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu-pointer.h for
 * linking dynamically with the userspace rcu library.
 *
 * 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/system.h>
#include <urcu/uatomic_arch.h>

/**
 * _rcu_dereference - reads (copy) a RCU-protected pointer to a local variable
 * into a RCU read-side critical section. The pointer can later be safely
 * dereferenced within the critical section.
 *
 * This ensures that the pointer copy is invariant thorough the whole critical
 * section.
 *
 * Inserts memory barriers on architectures that require them (currently only
 * Alpha) and documents which pointers are protected by RCU.
 *
 * The compiler memory barrier in LOAD_SHARED() ensures that value-speculative
 * optimizations (e.g. VSS: Value Speculation Scheduling) does not perform the
 * data read before the pointer read by speculating the value of the pointer.
 * Correct ordering is ensured because the pointer is read as a volatile access.
 * This acts as a global side-effect operation, which forbids reordering of
 * dependent memory operations. Note that such concern about dependency-breaking
 * optimizations will eventually be taken care of by the "memory_order_consume"
 * addition to forthcoming C++ standard.
 *
 * Should match rcu_assign_pointer() or rcu_xchg_pointer().
 */

#define _rcu_dereference(p)     ({					\
				typeof(p) _________p1 = LOAD_SHARED(p); \
				smp_read_barrier_depends();		\
				(_________p1);				\
				})

/**
 * _rcu_cmpxchg_pointer - same as rcu_assign_pointer, but tests if the pointer
 * is as expected by "old". If succeeds, returns the previous pointer to the
 * data structure, which can be safely freed after waiting for a quiescent state
 * using synchronize_rcu(). If fails (unexpected value), returns old (which
 * should not be freed !).
 */

#define _rcu_cmpxchg_pointer(p, old, _new)				\
	({								\
		typeof(*p) _________pold = (old);			\
		typeof(*p) _________pnew = (_new);			\
		if (!__builtin_constant_p(_new) ||			\
		    ((_new) != NULL))					\
			wmb();						\
		(likely(URCU_CAS_AVAIL()) ?				\
			(uatomic_cmpxchg(p, _________pold, _________pnew)) : \
			(compat_uatomic_cmpxchg(p, _________pold,	\
						_________pnew)))	\
	})

/**
 * _rcu_xchg_pointer - same as rcu_assign_pointer, but returns the previous
 * pointer to the data structure, which can be safely freed after waiting for a
 * quiescent state using synchronize_rcu().
 */

#define _rcu_xchg_pointer(p, v)				\
	({						\
		typeof(*p) _________pv = (v);		\
		if (!__builtin_constant_p(v) ||		\
		    ((v) != NULL))			\
			wmb();				\
		uatomic_xchg(p, _________pv);		\
	})


#define _rcu_set_pointer(p, v)				\
	({						\
		typeof(*p) _________pv = (v);		\
		if (!__builtin_constant_p(v) || 	\
		    ((v) != NULL))			\
			wmb();				\
		STORE_SHARED(*(p), _________pv);	\
	})

/**
 * _rcu_assign_pointer - assign (publicize) a pointer to a new data structure
 * meant to be read by RCU read-side critical sections. Returns the assigned
 * value.
 *
 * Documents which pointers will be dereferenced by RCU read-side critical
 * sections and adds the required memory barriers on architectures requiring
 * them. It also makes sure the compiler does not reorder code initializing the
 * data structure before its publication.
 *
 * Should match rcu_dereference_pointer().
 */

#define _rcu_assign_pointer(p, v)	_rcu_set_pointer(&(p), v)

#endif /* _URCU_POINTER_STATIC_H */
Commit	Line	Data
7e30abe3 MD	1	#ifndef _URCU_POINTER_STATIC_H
	2	#define _URCU_POINTER_STATIC_H
	3
	4	/*
	5	* urcu-pointer-static.h
	6	*
	7	* Userspace RCU header. Operations on pointers.
	8	*
	9	* TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu-pointer.h for
	10	* linking dynamically with the userspace rcu library.
	11	*
	12	* Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
	13	* Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
	14	*
	15	* This library is free software; you can redistribute it and/or
	16	* modify it under the terms of the GNU Lesser General Public
	17	* License as published by the Free Software Foundation; either
	18	* version 2.1 of the License, or (at your option) any later version.
	19	*
	20	* This library is distributed in the hope that it will be useful,
	21	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	22	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	23	* Lesser General Public License for more details.
	24	*
	25	* You should have received a copy of the GNU Lesser General Public
	26	* License along with this library; if not, write to the Free Software
	27	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	28	*
	29	* IBM's contributions to this file may be relicensed under LGPLv2 or later.
	30	*/
	31
	32	#include <urcu/compiler.h>
	33	#include <urcu/arch.h>
	34	#include <urcu/system.h>
48d848c7	35	#include <urcu/uatomic_arch.h>
7e30abe3 MD	36
	37	/**
	38	* _rcu_dereference - reads (copy) a RCU-protected pointer to a local variable
	39	* into a RCU read-side critical section. The pointer can later be safely
	40	* dereferenced within the critical section.
	41	*
	42	* This ensures that the pointer copy is invariant thorough the whole critical
	43	* section.
	44	*
	45	* Inserts memory barriers on architectures that require them (currently only
	46	* Alpha) and documents which pointers are protected by RCU.
	47	*
	48	* The compiler memory barrier in LOAD_SHARED() ensures that value-speculative
	49	* optimizations (e.g. VSS: Value Speculation Scheduling) does not perform the
	50	* data read before the pointer read by speculating the value of the pointer.
	51	* Correct ordering is ensured because the pointer is read as a volatile access.
	52	* This acts as a global side-effect operation, which forbids reordering of
	53	* dependent memory operations. Note that such concern about dependency-breaking
	54	* optimizations will eventually be taken care of by the "memory_order_consume"
	55	* addition to forthcoming C++ standard.
	56	*
	57	* Should match rcu_assign_pointer() or rcu_xchg_pointer().
	58	*/
	59
	60	#define _rcu_dereference(p) ({ \
	61	typeof(p) _________p1 = LOAD_SHARED(p); \
	62	smp_read_barrier_depends(); \
	63	(_________p1); \
	64	})
	65
	66	/**
	67	* _rcu_cmpxchg_pointer - same as rcu_assign_pointer, but tests if the pointer
	68	* is as expected by "old". If succeeds, returns the previous pointer to the
	69	* data structure, which can be safely freed after waiting for a quiescent state
	70	* using synchronize_rcu(). If fails (unexpected value), returns old (which
	71	* should not be freed !).
	72	*/
	73
2b5554c9 MD	74	#define _rcu_cmpxchg_pointer(p, old, _new) \
	75	({ \
	76	typeof(*p) _________pold = (old); \
	77	typeof(*p) _________pnew = (_new); \
	78	if (!__builtin_constant_p(_new) \|\| \
	79	((_new) != NULL)) \
	80	wmb(); \
e1562850 MD	81	(likely(URCU_CAS_AVAIL()) ? \
	82	(uatomic_cmpxchg(p, _________pold, _________pnew)) : \
	83	(compat_uatomic_cmpxchg(p, _________pold, \
	84	_________pnew))) \
7e30abe3 MD	85	})
	86
	87	/**
	88	* _rcu_xchg_pointer - same as rcu_assign_pointer, but returns the previous
	89	* pointer to the data structure, which can be safely freed after waiting for a
	90	* quiescent state using synchronize_rcu().
	91	*/
	92
	93	#define _rcu_xchg_pointer(p, v) \
	94	({ \
2b5554c9	95	typeof(*p) _________pv = (v); \
7e30abe3 MD	96	if (!__builtin_constant_p(v) \|\| \
	97	((v) != NULL)) \
	98	wmb(); \
2b5554c9	99	uatomic_xchg(p, _________pv); \
7e30abe3 MD	100	})
	101
	102
	103	#define _rcu_set_pointer(p, v) \
	104	({ \
2b5554c9	105	typeof(*p) _________pv = (v); \
7e30abe3 MD	106	if (!__builtin_constant_p(v) \|\| \
	107	((v) != NULL)) \
	108	wmb(); \
2b5554c9	109	STORE_SHARED(*(p), _________pv); \
7e30abe3 MD	110	})
7e30abe3 MD	111
7e30abe3 MD	112	/**
	113	* _rcu_assign_pointer - assign (publicize) a pointer to a new data structure
	114	* meant to be read by RCU read-side critical sections. Returns the assigned
	115	* value.
	116	*
	117	* Documents which pointers will be dereferenced by RCU read-side critical
	118	* sections and adds the required memory barriers on architectures requiring
	119	* them. It also makes sure the compiler does not reorder code initializing the
	120	* data structure before its publication.
	121	*
	122	* Should match rcu_dereference_pointer().
	123	*/
	124
	125	#define _rcu_assign_pointer(p, v) _rcu_set_pointer(&(p), v)
	126
	127	#endif /* _URCU_POINTER_STATIC_H */