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

#ifndef _URCU_QSBR_STATIC_H
#define _URCU_QSBR_STATIC_H

/*
 * urcu-qsbr-static.h
 *
 * Userspace RCU QSBR header.
 *
 * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu-qsbr.h for linking
 * dynamically with the userspace rcu QSBR 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 <stdlib.h>
#include <pthread.h>
#include <assert.h>

#include <compiler.h>
#include <arch.h>

/*
 * Identify a shared load. A smp_rmc() or smp_mc() should come before the load.
 */
#define _LOAD_SHARED(p)	       ACCESS_ONCE(p)

/*
 * Load a data from shared memory, doing a cache flush if required.
 */
#define LOAD_SHARED(p)			\
	({				\
		smp_rmc();		\
		_LOAD_SHARED(p);	\
	})

/*
 * Identify a shared store. A smp_wmc() or smp_mc() should follow the store.
 */
#define _STORE_SHARED(x, v)	({ ACCESS_ONCE(x) = (v); })

/*
 * Store v into x, where x is located in shared memory. Performs the required
 * cache flush after writing. Returns v.
 */
#define STORE_SHARED(x, v)		\
	({				\
		_STORE_SHARED(x, v);	\
		smp_wmc();		\
		(v);			\
	})

/**
 * _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.
 *
 * Should match rcu_assign_pointer() or rcu_xchg_pointer().
 */

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

/*
 * This code section can only be included in LGPL 2.1 compatible source code.
 * See below for the function call wrappers which can be used in code meant to
 * be only linked with the Userspace RCU library. This comes with a small
 * performance degradation on the read-side due to the added function calls.
 * This is required to permit relinking with newer versions of the library.
 */

/*
 * If a reader is really non-cooperative and refuses to commit its
 * rcu_reader_qs_gp count to memory (there is no barrier in the reader
 * per-se), kick it after a few loops waiting for it.
 */
#define KICK_READER_LOOPS 10000

#ifdef DEBUG_RCU
#define rcu_assert(args...)	assert(args)
#else
#define rcu_assert(args...)
#endif

#ifdef DEBUG_YIELD
#include <sched.h>
#include <time.h>
#include <pthread.h>
#include <unistd.h>

#define YIELD_READ 	(1 << 0)
#define YIELD_WRITE	(1 << 1)

/* maximum sleep delay, in us */
#define MAX_SLEEP 50

extern unsigned int yield_active;
extern unsigned int __thread rand_yield;

static inline void debug_yield_read(void)
{
	if (yield_active & YIELD_READ)
		if (rand_r(&rand_yield) & 0x1)
			usleep(rand_r(&rand_yield) % MAX_SLEEP);
}

static inline void debug_yield_write(void)
{
	if (yield_active & YIELD_WRITE)
		if (rand_r(&rand_yield) & 0x1)
			usleep(rand_r(&rand_yield) % MAX_SLEEP);
}

static inline void debug_yield_init(void)
{
	rand_yield = time(NULL) ^ pthread_self();
}
#else
static inline void debug_yield_read(void)
{
}

static inline void debug_yield_write(void)
{
}

static inline void debug_yield_init(void)
{

}
#endif

static inline void reader_barrier()
{
	smp_mb();
}

/*
 * Global quiescent period counter with low-order bits unused.
 * Using a int rather than a char to eliminate false register dependencies
 * causing stalls on some architectures.
 */
extern long urcu_gp_ctr;

extern long __thread rcu_reader_qs_gp;

static inline int rcu_gp_ongoing(long *value)
{
	if (value == NULL)
		return 0;

	return LOAD_SHARED(*value) & 1;
}

static inline void _rcu_read_lock(void)
{
	rcu_assert(rcu_reader_qs_gp & 1);
}

static inline void _rcu_read_unlock(void)
{
}

static inline void _rcu_quiescent_state(void)
{
	smp_mb();	
	rcu_reader_qs_gp = ACCESS_ONCE(urcu_gp_ctr) + 1;
	smp_mb();
}

static inline void _rcu_thread_offline(void)
{
	smp_mb();
	rcu_reader_qs_gp = ACCESS_ONCE(urcu_gp_ctr);
}

static inline void _rcu_thread_online(void)
{
	rcu_reader_qs_gp = ACCESS_ONCE(urcu_gp_ctr) + 1;
	smp_mb();
}

/**
 * _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)			\
	({						\
		if (!__builtin_constant_p(v) || 	\
		    ((v) != NULL))			\
			wmb();				\
		STORE_SHARED(p, v);			\
	})

/**
 * _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)				\
	({						\
		if (!__builtin_constant_p(v) ||		\
		    ((v) != NULL))			\
			wmb();				\
		xchg(p, v);				\
	})

/*
 * Exchanges the pointer and waits for quiescent state.
 * The pointer returned can be freed.
 */
#define _rcu_publish_content(p, v)			\
	({						\
		void *oldptr;				\
		oldptr = _rcu_xchg_pointer(p, v);	\
		synchronize_rcu();			\
		oldptr;					\
	})

#endif /* _URCU_QSBR_STATIC_H */
Commit	Line	Data
	1	#ifndef _URCU_QSBR_STATIC_H
	2	#define _URCU_QSBR_STATIC_H
	3
	4	/*
	5	* urcu-qsbr-static.h
	6	*
	7	* Userspace RCU QSBR header.
	8	*
	9	* TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu-qsbr.h for linking
	10	* dynamically with the userspace rcu QSBR 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 <stdlib.h>
	33	#include <pthread.h>
	34	#include <assert.h>
	35
	36	#include <compiler.h>
	37	#include <arch.h>
	38
	39	/*
	40	* Identify a shared load. A smp_rmc() or smp_mc() should come before the load.
	41	*/
	42	#define _LOAD_SHARED(p) ACCESS_ONCE(p)
	43
	44	/*
	45	* Load a data from shared memory, doing a cache flush if required.
	46	*/
	47	#define LOAD_SHARED(p) \
	48	({ \
	49	smp_rmc(); \
	50	_LOAD_SHARED(p); \
	51	})
	52
	53	/*
	54	* Identify a shared store. A smp_wmc() or smp_mc() should follow the store.
	55	*/
	56	#define _STORE_SHARED(x, v) ({ ACCESS_ONCE(x) = (v); })
	57
	58	/*
	59	* Store v into x, where x is located in shared memory. Performs the required
	60	* cache flush after writing. Returns v.
	61	*/
	62	#define STORE_SHARED(x, v) \
	63	({ \
	64	_STORE_SHARED(x, v); \
	65	smp_wmc(); \
	66	(v); \
	67	})
	68
	69	/**
	70	* _rcu_dereference - reads (copy) a RCU-protected pointer to a local variable
	71	* into a RCU read-side critical section. The pointer can later be safely
	72	* dereferenced within the critical section.
	73	*
	74	* This ensures that the pointer copy is invariant thorough the whole critical
	75	* section.
	76	*
	77	* Inserts memory barriers on architectures that require them (currently only
	78	* Alpha) and documents which pointers are protected by RCU.
	79	*
	80	* Should match rcu_assign_pointer() or rcu_xchg_pointer().
	81	*/
	82
	83	#define _rcu_dereference(p) ({ \
	84	typeof(p) _________p1 = LOAD_SHARED(p); \
	85	smp_read_barrier_depends(); \
	86	(_________p1); \
	87	})
	88
	89	/*
	90	* This code section can only be included in LGPL 2.1 compatible source code.
	91	* See below for the function call wrappers which can be used in code meant to
	92	* be only linked with the Userspace RCU library. This comes with a small
	93	* performance degradation on the read-side due to the added function calls.
	94	* This is required to permit relinking with newer versions of the library.
	95	*/
	96
	97	/*
	98	* If a reader is really non-cooperative and refuses to commit its
	99	* rcu_reader_qs_gp count to memory (there is no barrier in the reader
	100	* per-se), kick it after a few loops waiting for it.
	101	*/
	102	#define KICK_READER_LOOPS 10000
	103
	104	#ifdef DEBUG_RCU
	105	#define rcu_assert(args...) assert(args)
	106	#else
	107	#define rcu_assert(args...)
	108	#endif
	109
	110	#ifdef DEBUG_YIELD
	111	#include <sched.h>
	112	#include <time.h>
	113	#include <pthread.h>
	114	#include <unistd.h>
	115
	116	#define YIELD_READ (1 << 0)
	117	#define YIELD_WRITE (1 << 1)
	118
	119	/* maximum sleep delay, in us */
	120	#define MAX_SLEEP 50
	121
	122	extern unsigned int yield_active;
	123	extern unsigned int __thread rand_yield;
	124
	125	static inline void debug_yield_read(void)
	126	{
	127	if (yield_active & YIELD_READ)
	128	if (rand_r(&rand_yield) & 0x1)
	129	usleep(rand_r(&rand_yield) % MAX_SLEEP);
	130	}
	131
	132	static inline void debug_yield_write(void)
	133	{
	134	if (yield_active & YIELD_WRITE)
	135	if (rand_r(&rand_yield) & 0x1)
	136	usleep(rand_r(&rand_yield) % MAX_SLEEP);
	137	}
	138
	139	static inline void debug_yield_init(void)
	140	{
	141	rand_yield = time(NULL) ^ pthread_self();
	142	}
	143	#else
	144	static inline void debug_yield_read(void)
	145	{
	146	}
	147
	148	static inline void debug_yield_write(void)
	149	{
	150	}
	151
	152	static inline void debug_yield_init(void)
	153	{
	154
	155	}
	156	#endif
	157
	158	static inline void reader_barrier()
	159	{
	160	smp_mb();
	161	}
	162
	163	/*
	164	* Global quiescent period counter with low-order bits unused.
	165	* Using a int rather than a char to eliminate false register dependencies
	166	* causing stalls on some architectures.
	167	*/
	168	extern long urcu_gp_ctr;
	169
	170	extern long __thread rcu_reader_qs_gp;
	171
	172	static inline int rcu_gp_ongoing(long *value)
	173	{
	174	if (value == NULL)
	175	return 0;
	176
	177	return LOAD_SHARED(*value) & 1;
	178	}
	179
	180	static inline void _rcu_read_lock(void)
	181	{
	182	rcu_assert(rcu_reader_qs_gp & 1);
	183	}
	184
	185	static inline void _rcu_read_unlock(void)
	186	{
	187	}
	188
	189	static inline void _rcu_quiescent_state(void)
	190	{
	191	smp_mb();
	192	rcu_reader_qs_gp = ACCESS_ONCE(urcu_gp_ctr) + 1;
	193	smp_mb();
	194	}
	195
	196	static inline void _rcu_thread_offline(void)
	197	{
	198	smp_mb();
	199	rcu_reader_qs_gp = ACCESS_ONCE(urcu_gp_ctr);
	200	}
	201
	202	static inline void _rcu_thread_online(void)
	203	{
	204	rcu_reader_qs_gp = ACCESS_ONCE(urcu_gp_ctr) + 1;
	205	smp_mb();
	206	}
	207
	208	/**
	209	* _rcu_assign_pointer - assign (publicize) a pointer to a new data structure
	210	* meant to be read by RCU read-side critical sections. Returns the assigned
	211	* value.
	212	*
	213	* Documents which pointers will be dereferenced by RCU read-side critical
	214	* sections and adds the required memory barriers on architectures requiring
	215	* them. It also makes sure the compiler does not reorder code initializing the
	216	* data structure before its publication.
	217	*
	218	* Should match rcu_dereference_pointer().
	219	*/
	220
	221	#define _rcu_assign_pointer(p, v) \
	222	({ \
	223	if (!__builtin_constant_p(v) \|\| \
	224	((v) != NULL)) \
	225	wmb(); \
	226	STORE_SHARED(p, v); \
	227	})
	228
	229	/**
	230	* _rcu_xchg_pointer - same as rcu_assign_pointer, but returns the previous
	231	* pointer to the data structure, which can be safely freed after waiting for a
	232	* quiescent state using synchronize_rcu().
	233	*/
	234
	235	#define _rcu_xchg_pointer(p, v) \
	236	({ \
	237	if (!__builtin_constant_p(v) \|\| \
	238	((v) != NULL)) \
	239	wmb(); \
	240	xchg(p, v); \
	241	})
	242
	243	/*
	244	* Exchanges the pointer and waits for quiescent state.
	245	* The pointer returned can be freed.
	246	*/
	247	#define _rcu_publish_content(p, v) \
	248	({ \
	249	void *oldptr; \
	250	oldptr = _rcu_xchg_pointer(p, v); \
	251	synchronize_rcu(); \
	252	oldptr; \
	253	})
	254
	255	#endif /* _URCU_QSBR_STATIC_H */