[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 <syscall.h>
#include <unistd.h>

#include <urcu/compiler.h>
#include <urcu/arch.h>
#include <urcu/list.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);				\
				})

#define futex(...)		syscall(__NR_futex, __VA_ARGS__)
#define FUTEX_WAIT		0
#define FUTEX_WAKE		1

/*
 * 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
 * urcu_reader.ctr 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 futex().
 */
#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_CTR		(1UL << 1)

/*
 * 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 {
	unsigned long ctr;
	struct list_head head;
	pthread_t tid;
};

extern struct urcu_reader __thread urcu_reader;

extern int gp_futex;

/*
 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
 */
static inline void wake_up_gp(void)
{
	if (unlikely(uatomic_read(&gp_futex) == -1)) {
		uatomic_set(&gp_futex, 0);
		futex(&gp_futex, FUTEX_WAKE, 1,
		      NULL, NULL, 0);
	}
}

#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.ctr);
}

static inline void _rcu_read_unlock(void)
{
}

static inline void _rcu_quiescent_state(void)
{
	smp_mb();	
	_STORE_SHARED(urcu_reader.ctr, _LOAD_SHARED(urcu_gp_ctr));
	smp_mb();	/* write urcu_reader.ctr before read futex */
	wake_up_gp();
	smp_mb();
}

static inline void _rcu_thread_offline(void)
{
	smp_mb();
	STORE_SHARED(urcu_reader.ctr, 0);
	smp_mb();	/* write urcu_reader.ctr before read futex */
	wake_up_gp();
}

static inline void _rcu_thread_online(void)
{
	_STORE_SHARED(urcu_reader.ctr, LOAD_SHARED(urcu_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();				\
		uatomic_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();				\
		uatomic_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>
bc6c15bb MD	36	#include <syscall.h>
bc6c15bb MD	37	#include <unistd.h>
7ac06cef	38
ec4e58a3 MD	39	#include <urcu/compiler.h>
ec4e58a3 MD	40	#include <urcu/arch.h>
4f8e3380	41	#include <urcu/list.h>
7ac06cef MD	42
	43	/*
	44	* Identify a shared load. A smp_rmc() or smp_mc() should come before the load.
	45	*/
	46	#define _LOAD_SHARED(p) ACCESS_ONCE(p)
	47
	48	/*
	49	* Load a data from shared memory, doing a cache flush if required.
	50	*/
	51	#define LOAD_SHARED(p) \
	52	({ \
	53	smp_rmc(); \
	54	_LOAD_SHARED(p); \
	55	})
	56
	57	/*
	58	* Identify a shared store. A smp_wmc() or smp_mc() should follow the store.
	59	*/
	60	#define _STORE_SHARED(x, v) ({ ACCESS_ONCE(x) = (v); })
	61
	62	/*
	63	* Store v into x, where x is located in shared memory. Performs the required
	64	* cache flush after writing. Returns v.
	65	*/
	66	#define STORE_SHARED(x, v) \
	67	({ \
	68	_STORE_SHARED(x, v); \
	69	smp_wmc(); \
	70	(v); \
	71	})
	72
	73	/**
	74	* _rcu_dereference - reads (copy) a RCU-protected pointer to a local variable
	75	* into a RCU read-side critical section. The pointer can later be safely
	76	* dereferenced within the critical section.
	77	*
	78	* This ensures that the pointer copy is invariant thorough the whole critical
	79	* section.
	80	*
	81	* Inserts memory barriers on architectures that require them (currently only
	82	* Alpha) and documents which pointers are protected by RCU.
	83	*
	84	* Should match rcu_assign_pointer() or rcu_xchg_pointer().
	85	*/
	86
	87	#define _rcu_dereference(p) ({ \
	88	typeof(p) _________p1 = LOAD_SHARED(p); \
	89	smp_read_barrier_depends(); \
	90	(_________p1); \
	91	})
	92
bc6c15bb MD	93	#define futex(...) syscall(__NR_futex, __VA_ARGS__)
	94	#define FUTEX_WAIT 0
	95	#define FUTEX_WAKE 1
	96
7ac06cef MD	97	/*
	98	* This code section can only be included in LGPL 2.1 compatible source code.
	99	* See below for the function call wrappers which can be used in code meant to
	100	* be only linked with the Userspace RCU library. This comes with a small
	101	* performance degradation on the read-side due to the added function calls.
	102	* This is required to permit relinking with newer versions of the library.
	103	*/
	104
	105	/*
	106	* If a reader is really non-cooperative and refuses to commit its
4f8e3380	107	* urcu_reader.ctr count to memory (there is no barrier in the reader
7ac06cef MD	108	* per-se), kick it after a few loops waiting for it.
	109	*/
	110	#define KICK_READER_LOOPS 10000
	111
bc6c15bb MD	112	/*
	113	* Active attempts to check for reader Q.S. before calling futex().
	114	*/
	115	#define RCU_QS_ACTIVE_ATTEMPTS 100
	116
7ac06cef MD	117	#ifdef DEBUG_RCU
	118	#define rcu_assert(args...) assert(args)
	119	#else
	120	#define rcu_assert(args...)
	121	#endif
	122
	123	#ifdef DEBUG_YIELD
	124	#include <sched.h>
	125	#include <time.h>
	126	#include <pthread.h>
	127	#include <unistd.h>
	128
	129	#define YIELD_READ (1 << 0)
	130	#define YIELD_WRITE (1 << 1)
	131
	132	/* maximum sleep delay, in us */
	133	#define MAX_SLEEP 50
	134
	135	extern unsigned int yield_active;
	136	extern unsigned int __thread rand_yield;
	137
	138	static inline void debug_yield_read(void)
	139	{
	140	if (yield_active & YIELD_READ)
	141	if (rand_r(&rand_yield) & 0x1)
	142	usleep(rand_r(&rand_yield) % MAX_SLEEP);
	143	}
	144
	145	static inline void debug_yield_write(void)
	146	{
	147	if (yield_active & YIELD_WRITE)
	148	if (rand_r(&rand_yield) & 0x1)
	149	usleep(rand_r(&rand_yield) % MAX_SLEEP);
	150	}
	151
	152	static inline void debug_yield_init(void)
	153	{
	154	rand_yield = time(NULL) ^ pthread_self();
	155	}
	156	#else
	157	static inline void debug_yield_read(void)
	158	{
	159	}
	160
	161	static inline void debug_yield_write(void)
	162	{
	163	}
	164
	165	static inline void debug_yield_init(void)
	166	{
	167
	168	}
	169	#endif
	170
	171	static inline void reader_barrier()
	172	{
	173	smp_mb();
	174	}
	175
ac258107	176	#define RCU_GP_ONLINE (1UL << 0)
55570466	177	#define RCU_GP_CTR (1UL << 1)
ac258107	178
7ac06cef MD	179	/*
	180	* Global quiescent period counter with low-order bits unused.
	181	* Using a int rather than a char to eliminate false register dependencies
	182	* causing stalls on some architectures.
	183	*/
f0f7dbdd	184	extern unsigned long urcu_gp_ctr;
7ac06cef	185
4f8e3380 MD	186	struct urcu_reader {
	187	unsigned long ctr;
	188	struct list_head head;
	189	pthread_t tid;
	190	};
	191
	192	extern struct urcu_reader __thread urcu_reader;
7ac06cef	193
bc6c15bb MD	194	extern int gp_futex;
	195
	196	/*
	197	* Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
	198	*/
	199	static inline void wake_up_gp(void)
	200	{
ec4e58a3 MD	201	if (unlikely(uatomic_read(&gp_futex) == -1)) {
ec4e58a3 MD	202	uatomic_set(&gp_futex, 0);
bc6c15bb MD	203	futex(&gp_futex, FUTEX_WAKE, 1,
	204	NULL, NULL, 0);
	205	}
	206	}
	207
47d2f29e MD	208	#if (BITS_PER_LONG < 64)
	209	static inline int rcu_gp_ongoing(unsigned long *value)
	210	{
	211	unsigned long reader_gp;
	212
	213	if (value == NULL)
	214	return 0;
	215	reader_gp = LOAD_SHARED(*value);
	216	return reader_gp && ((reader_gp ^ urcu_gp_ctr) & RCU_GP_CTR);
	217	}
	218	#else /* !(BITS_PER_LONG < 64) */
f0f7dbdd	219	static inline int rcu_gp_ongoing(unsigned long *value)
7ac06cef	220	{
f0f7dbdd	221	unsigned long reader_gp;
4e560c17	222
7ac06cef MD	223	if (value == NULL)
7ac06cef MD	224	return 0;
4e560c17	225	reader_gp = LOAD_SHARED(*value);
f0f7dbdd	226	return reader_gp && (reader_gp - urcu_gp_ctr > ULONG_MAX / 2);
7ac06cef	227	}
47d2f29e	228	#endif /* !(BITS_PER_LONG < 64) */
7ac06cef MD	229
	230	static inline void _rcu_read_lock(void)
	231	{
4f8e3380	232	rcu_assert(urcu_reader.ctr);
7ac06cef MD	233	}
	234
	235	static inline void _rcu_read_unlock(void)
	236	{
	237	}
	238
	239	static inline void _rcu_quiescent_state(void)
	240	{
	241	smp_mb();
4f8e3380 MD	242	_STORE_SHARED(urcu_reader.ctr, _LOAD_SHARED(urcu_gp_ctr));
4f8e3380 MD	243	smp_mb(); /* write urcu_reader.ctr before read futex */
bc6c15bb	244	wake_up_gp();
7ac06cef MD	245	smp_mb();
	246	}
	247
	248	static inline void _rcu_thread_offline(void)
	249	{
	250	smp_mb();
4f8e3380 MD	251	STORE_SHARED(urcu_reader.ctr, 0);
4f8e3380 MD	252	smp_mb(); /* write urcu_reader.ctr before read futex */
bc6c15bb	253	wake_up_gp();
7ac06cef MD	254	}
	255
	256	static inline void _rcu_thread_online(void)
	257	{
4f8e3380	258	_STORE_SHARED(urcu_reader.ctr, LOAD_SHARED(urcu_gp_ctr));
7ac06cef MD	259	smp_mb();
	260	}
	261
	262	/**
	263	* _rcu_assign_pointer - assign (publicize) a pointer to a new data structure
	264	* meant to be read by RCU read-side critical sections. Returns the assigned
	265	* value.
	266	*
	267	* Documents which pointers will be dereferenced by RCU read-side critical
	268	* sections and adds the required memory barriers on architectures requiring
	269	* them. It also makes sure the compiler does not reorder code initializing the
	270	* data structure before its publication.
	271	*
	272	* Should match rcu_dereference_pointer().
	273	*/
	274
	275	#define _rcu_assign_pointer(p, v) \
	276	({ \
	277	if (!__builtin_constant_p(v) \|\| \
	278	((v) != NULL)) \
	279	wmb(); \
	280	STORE_SHARED(p, v); \
	281	})
	282
4d1ce26f MD	283	/**
	284	* _rcu_cmpxchg_pointer - same as rcu_assign_pointer, but tests if the pointer
	285	* is as expected by "old". If succeeds, returns the previous pointer to the
	286	* data structure, which can be safely freed after waiting for a quiescent state
	287	* using synchronize_rcu(). If fails (unexpected value), returns old (which
	288	* should not be freed !).
	289	*/
	290
	291	#define _rcu_cmpxchg_pointer(p, old, _new) \
	292	({ \
	293	if (!__builtin_constant_p(_new) \|\| \
	294	((_new) != NULL)) \
	295	wmb(); \
ec4e58a3	296	uatomic_cmpxchg(p, old, _new); \
4d1ce26f MD	297	})
4d1ce26f MD	298
7ac06cef MD	299	/**
	300	* _rcu_xchg_pointer - same as rcu_assign_pointer, but returns the previous
	301	* pointer to the data structure, which can be safely freed after waiting for a
	302	* quiescent state using synchronize_rcu().
	303	*/
	304
	305	#define _rcu_xchg_pointer(p, v) \
	306	({ \
	307	if (!__builtin_constant_p(v) \|\| \
	308	((v) != NULL)) \
	309	wmb(); \
ec4e58a3	310	uatomic_xchg(p, v); \
7ac06cef MD	311	})
	312
	313	/*
	314	* Exchanges the pointer and waits for quiescent state.
	315	* The pointer returned can be freed.
	316	*/
	317	#define _rcu_publish_content(p, v) \
	318	({ \
	319	void *oldptr; \
	320	oldptr = _rcu_xchg_pointer(p, v); \
	321	synchronize_rcu(); \
	322	oldptr; \
	323	})
	324
	325	#endif /* _URCU_QSBR_STATIC_H */