[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 <limits.h>
#include <sched.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

/*
 * Active attempts to check for reader Q.S. before calling sched_yield().
 */
#define RCU_QS_ACTIVE_ATTEMPTS 100

#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();
}

#define RCU_GP_ONLINE		(1UL << 0)
#define RCU_GP_ONGOING		(1UL << 1)
#define RCU_GP_CTR		(1UL << 2)

/*
 * 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 unsigned long urcu_gp_ctr;

struct urcu_reader_status {
	unsigned long qs_gp;
	unsigned long gp_waiting;
};

extern struct urcu_reader_status __thread urcu_reader_status;

#if (BITS_PER_LONG < 64)
static inline int rcu_gp_ongoing(unsigned long *value)
{
	unsigned long reader_gp;

	if (value == NULL)
		return 0;
	reader_gp = LOAD_SHARED(*value);
	return reader_gp && ((reader_gp ^ urcu_gp_ctr) & RCU_GP_CTR);
}
#else /* !(BITS_PER_LONG < 64) */
static inline int rcu_gp_ongoing(unsigned long *value)
{
	unsigned long reader_gp;

	if (value == NULL)
		return 0;
	reader_gp = LOAD_SHARED(*value);
	return reader_gp && (reader_gp - urcu_gp_ctr > ULONG_MAX / 2);
}
#endif  /* !(BITS_PER_LONG < 64) */

static inline void _rcu_read_lock(void)
{
	rcu_assert(urcu_reader_status.qs_gp);
}

static inline void _rcu_read_unlock(void)
{
}

static inline void _rcu_quiescent_state(void)
{
	long gp_ctr;

	smp_mb();
	/*
	 * volatile accesses can be reordered by the compiler when put in the
	 * same expression.
	 */
	if (unlikely((gp_ctr = LOAD_SHARED(urcu_gp_ctr)) & RCU_GP_ONGOING) &&
	    unlikely(urcu_reader_status.gp_waiting)) {
		_STORE_SHARED(urcu_reader_status.qs_gp, gp_ctr);
		sched_yield();
	} else {
		_STORE_SHARED(urcu_reader_status.qs_gp, gp_ctr);
	}
	smp_mb();
}

static inline void _rcu_thread_offline(void)
{
	smp_mb();
	STORE_SHARED(urcu_reader_status.qs_gp, 0);
}

static inline void _rcu_thread_online(void)
{
	long gp_ctr;

	if (unlikely((gp_ctr = LOAD_SHARED(urcu_gp_ctr)) & RCU_GP_ONGOING) &&
	    unlikely(urcu_reader_status.gp_waiting)) {
		sched_yield();
		gp_ctr = LOAD_SHARED(urcu_gp_ctr);
	}
	_STORE_SHARED(urcu_reader_status.qs_gp, gp_ctr);
	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_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)		\
	({						\
		if (!__builtin_constant_p(_new) ||	\
		    ((_new) != NULL))			\
			wmb();				\
		cmpxchg(p, old, _new);			\
	})

/**
 * _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
7ac06cef MD	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>
f0f7dbdd	35	#include <limits.h>
ae62b5e8	36	#include <sched.h>
7ac06cef MD	37
	38	#include <compiler.h>
	39	#include <arch.h>
	40
	41	/*
	42	* Identify a shared load. A smp_rmc() or smp_mc() should come before the load.
	43	*/
	44	#define _LOAD_SHARED(p) ACCESS_ONCE(p)
	45
	46	/*
	47	* Load a data from shared memory, doing a cache flush if required.
	48	*/
	49	#define LOAD_SHARED(p) \
	50	({ \
	51	smp_rmc(); \
	52	_LOAD_SHARED(p); \
	53	})
	54
	55	/*
	56	* Identify a shared store. A smp_wmc() or smp_mc() should follow the store.
	57	*/
	58	#define _STORE_SHARED(x, v) ({ ACCESS_ONCE(x) = (v); })
	59
	60	/*
	61	* Store v into x, where x is located in shared memory. Performs the required
	62	* cache flush after writing. Returns v.
	63	*/
	64	#define STORE_SHARED(x, v) \
	65	({ \
	66	_STORE_SHARED(x, v); \
	67	smp_wmc(); \
	68	(v); \
	69	})
	70
	71	/**
	72	* _rcu_dereference - reads (copy) a RCU-protected pointer to a local variable
	73	* into a RCU read-side critical section. The pointer can later be safely
	74	* dereferenced within the critical section.
	75	*
	76	* This ensures that the pointer copy is invariant thorough the whole critical
	77	* section.
	78	*
	79	* Inserts memory barriers on architectures that require them (currently only
	80	* Alpha) and documents which pointers are protected by RCU.
	81	*
	82	* Should match rcu_assign_pointer() or rcu_xchg_pointer().
	83	*/
	84
	85	#define _rcu_dereference(p) ({ \
	86	typeof(p) _________p1 = LOAD_SHARED(p); \
	87	smp_read_barrier_depends(); \
	88	(_________p1); \
	89	})
	90
	91	/*
	92	* This code section can only be included in LGPL 2.1 compatible source code.
	93	* See below for the function call wrappers which can be used in code meant to
	94	* be only linked with the Userspace RCU library. This comes with a small
	95	* performance degradation on the read-side due to the added function calls.
	96	* This is required to permit relinking with newer versions of the library.
	97	*/
	98
	99	/*
	100	* If a reader is really non-cooperative and refuses to commit its
8b25e300	101	* rcu_reader qs_gp count to memory (there is no barrier in the reader
7ac06cef MD	102	* per-se), kick it after a few loops waiting for it.
	103	*/
	104	#define KICK_READER_LOOPS 10000
	105
bc6c15bb	106	/*
ae62b5e8	107	* Active attempts to check for reader Q.S. before calling sched_yield().
bc6c15bb MD	108	*/
	109	#define RCU_QS_ACTIVE_ATTEMPTS 100
	110
7ac06cef MD	111	#ifdef DEBUG_RCU
	112	#define rcu_assert(args...) assert(args)
	113	#else
	114	#define rcu_assert(args...)
	115	#endif
	116
	117	#ifdef DEBUG_YIELD
	118	#include <sched.h>
	119	#include <time.h>
	120	#include <pthread.h>
	121	#include <unistd.h>
	122
	123	#define YIELD_READ (1 << 0)
	124	#define YIELD_WRITE (1 << 1)
	125
	126	/* maximum sleep delay, in us */
	127	#define MAX_SLEEP 50
	128
	129	extern unsigned int yield_active;
	130	extern unsigned int __thread rand_yield;
	131
	132	static inline void debug_yield_read(void)
	133	{
	134	if (yield_active & YIELD_READ)
	135	if (rand_r(&rand_yield) & 0x1)
	136	usleep(rand_r(&rand_yield) % MAX_SLEEP);
	137	}
	138
	139	static inline void debug_yield_write(void)
	140	{
	141	if (yield_active & YIELD_WRITE)
	142	if (rand_r(&rand_yield) & 0x1)
	143	usleep(rand_r(&rand_yield) % MAX_SLEEP);
	144	}
	145
	146	static inline void debug_yield_init(void)
	147	{
	148	rand_yield = time(NULL) ^ pthread_self();
	149	}
	150	#else
	151	static inline void debug_yield_read(void)
	152	{
	153	}
	154
	155	static inline void debug_yield_write(void)
	156	{
	157	}
	158
	159	static inline void debug_yield_init(void)
	160	{
	161
	162	}
	163	#endif
	164
	165	static inline void reader_barrier()
	166	{
	167	smp_mb();
	168	}
	169
ac258107	170	#define RCU_GP_ONLINE (1UL << 0)
ae62b5e8 MD	171	#define RCU_GP_ONGOING (1UL << 1)
ae62b5e8 MD	172	#define RCU_GP_CTR (1UL << 2)
ac258107	173
7ac06cef MD	174	/*
	175	* Global quiescent period counter with low-order bits unused.
	176	* Using a int rather than a char to eliminate false register dependencies
	177	* causing stalls on some architectures.
	178	*/
f0f7dbdd	179	extern unsigned long urcu_gp_ctr;
7ac06cef	180
8b25e300 MD	181	struct urcu_reader_status {
	182	unsigned long qs_gp;
	183	unsigned long gp_waiting;
	184	};
	185
	186	extern struct urcu_reader_status __thread urcu_reader_status;
7ac06cef	187
47d2f29e MD	188	#if (BITS_PER_LONG < 64)
	189	static inline int rcu_gp_ongoing(unsigned long *value)
	190	{
	191	unsigned long reader_gp;
	192
	193	if (value == NULL)
	194	return 0;
	195	reader_gp = LOAD_SHARED(*value);
	196	return reader_gp && ((reader_gp ^ urcu_gp_ctr) & RCU_GP_CTR);
	197	}
	198	#else /* !(BITS_PER_LONG < 64) */
f0f7dbdd	199	static inline int rcu_gp_ongoing(unsigned long *value)
7ac06cef	200	{
f0f7dbdd	201	unsigned long reader_gp;
4e560c17	202
7ac06cef MD	203	if (value == NULL)
7ac06cef MD	204	return 0;
4e560c17	205	reader_gp = LOAD_SHARED(*value);
f0f7dbdd	206	return reader_gp && (reader_gp - urcu_gp_ctr > ULONG_MAX / 2);
7ac06cef	207	}
47d2f29e	208	#endif /* !(BITS_PER_LONG < 64) */
7ac06cef MD	209
	210	static inline void _rcu_read_lock(void)
	211	{
8b25e300	212	rcu_assert(urcu_reader_status.qs_gp);
7ac06cef MD	213	}
	214
	215	static inline void _rcu_read_unlock(void)
	216	{
	217	}
	218
	219	static inline void _rcu_quiescent_state(void)
	220	{
ae62b5e8 MD	221	long gp_ctr;
	222
	223	smp_mb();
8b25e300 MD	224	/*
	225	* volatile accesses can be reordered by the compiler when put in the
	226	* same expression.
	227	*/
	228	if (unlikely((gp_ctr = LOAD_SHARED(urcu_gp_ctr)) & RCU_GP_ONGOING) &&
	229	unlikely(urcu_reader_status.gp_waiting)) {
	230	_STORE_SHARED(urcu_reader_status.qs_gp, gp_ctr);
ae62b5e8	231	sched_yield();
8b25e300 MD	232	} else {
8b25e300 MD	233	_STORE_SHARED(urcu_reader_status.qs_gp, gp_ctr);
ae62b5e8	234	}
7ac06cef MD	235	smp_mb();
	236	}
	237
	238	static inline void _rcu_thread_offline(void)
	239	{
	240	smp_mb();
8b25e300	241	STORE_SHARED(urcu_reader_status.qs_gp, 0);
7ac06cef MD	242	}
	243
	244	static inline void _rcu_thread_online(void)
	245	{
ae62b5e8 MD	246	long gp_ctr;
ae62b5e8 MD	247
8b25e300 MD	248	if (unlikely((gp_ctr = LOAD_SHARED(urcu_gp_ctr)) & RCU_GP_ONGOING) &&
8b25e300 MD	249	unlikely(urcu_reader_status.gp_waiting)) {
ae62b5e8 MD	250	sched_yield();
	251	gp_ctr = LOAD_SHARED(urcu_gp_ctr);
	252	}
8b25e300	253	_STORE_SHARED(urcu_reader_status.qs_gp, gp_ctr);
7ac06cef MD	254	smp_mb();
	255	}
	256
	257	/**
	258	* _rcu_assign_pointer - assign (publicize) a pointer to a new data structure
	259	* meant to be read by RCU read-side critical sections. Returns the assigned
	260	* value.
	261	*
	262	* Documents which pointers will be dereferenced by RCU read-side critical
	263	* sections and adds the required memory barriers on architectures requiring
	264	* them. It also makes sure the compiler does not reorder code initializing the
	265	* data structure before its publication.
	266	*
	267	* Should match rcu_dereference_pointer().
	268	*/
	269
	270	#define _rcu_assign_pointer(p, v) \
	271	({ \
	272	if (!__builtin_constant_p(v) \|\| \
	273	((v) != NULL)) \
	274	wmb(); \
	275	STORE_SHARED(p, v); \
	276	})
	277
4d1ce26f MD	278	/**
	279	* _rcu_cmpxchg_pointer - same as rcu_assign_pointer, but tests if the pointer
	280	* is as expected by "old". If succeeds, returns the previous pointer to the
	281	* data structure, which can be safely freed after waiting for a quiescent state
	282	* using synchronize_rcu(). If fails (unexpected value), returns old (which
	283	* should not be freed !).
	284	*/
	285
	286	#define _rcu_cmpxchg_pointer(p, old, _new) \
	287	({ \
	288	if (!__builtin_constant_p(_new) \|\| \
	289	((_new) != NULL)) \
	290	wmb(); \
	291	cmpxchg(p, old, _new); \
	292	})
	293
7ac06cef MD	294	/**
	295	* _rcu_xchg_pointer - same as rcu_assign_pointer, but returns the previous
	296	* pointer to the data structure, which can be safely freed after waiting for a
	297	* quiescent state using synchronize_rcu().
	298	*/
	299
	300	#define _rcu_xchg_pointer(p, v) \
	301	({ \
	302	if (!__builtin_constant_p(v) \|\| \
	303	((v) != NULL)) \
	304	wmb(); \
	305	xchg(p, v); \
	306	})
	307
	308	/*
	309	* Exchanges the pointer and waits for quiescent state.
	310	* The pointer returned can be freed.
	311	*/
	312	#define _rcu_publish_content(p, v) \
	313	({ \
	314	void *oldptr; \
	315	oldptr = _rcu_xchg_pointer(p, v); \
	316	synchronize_rcu(); \
	317	oldptr; \
	318	})
	319
	320	#endif /* _URCU_QSBR_STATIC_H */