[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/arch_uatomic.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 {
	/* Data used by both reader and synchronize_rcu() */
	unsigned long ctr;
	/* Data used for registry */
	struct list_head head __attribute__((aligned(CACHE_LINE_SIZE)));
	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>
1ccf9cbe	41	#include <urcu/arch_uatomic.h>
4f8e3380	42	#include <urcu/list.h>
7ac06cef MD	43
	44	/*
	45	* Identify a shared load. A smp_rmc() or smp_mc() should come before the load.
	46	*/
	47	#define _LOAD_SHARED(p) ACCESS_ONCE(p)
	48
	49	/*
	50	* Load a data from shared memory, doing a cache flush if required.
	51	*/
	52	#define LOAD_SHARED(p) \
	53	({ \
	54	smp_rmc(); \
	55	_LOAD_SHARED(p); \
	56	})
	57
	58	/*
	59	* Identify a shared store. A smp_wmc() or smp_mc() should follow the store.
	60	*/
	61	#define _STORE_SHARED(x, v) ({ ACCESS_ONCE(x) = (v); })
	62
	63	/*
	64	* Store v into x, where x is located in shared memory. Performs the required
	65	* cache flush after writing. Returns v.
	66	*/
	67	#define STORE_SHARED(x, v) \
	68	({ \
	69	_STORE_SHARED(x, v); \
	70	smp_wmc(); \
	71	(v); \
	72	})
	73
	74	/**
	75	* _rcu_dereference - reads (copy) a RCU-protected pointer to a local variable
	76	* into a RCU read-side critical section. The pointer can later be safely
	77	* dereferenced within the critical section.
	78	*
	79	* This ensures that the pointer copy is invariant thorough the whole critical
	80	* section.
	81	*
	82	* Inserts memory barriers on architectures that require them (currently only
	83	* Alpha) and documents which pointers are protected by RCU.
	84	*
	85	* Should match rcu_assign_pointer() or rcu_xchg_pointer().
	86	*/
	87
	88	#define _rcu_dereference(p) ({ \
	89	typeof(p) _________p1 = LOAD_SHARED(p); \
	90	smp_read_barrier_depends(); \
	91	(_________p1); \
	92	})
	93
bc6c15bb MD	94	#define futex(...) syscall(__NR_futex, __VA_ARGS__)
	95	#define FUTEX_WAIT 0
	96	#define FUTEX_WAKE 1
	97
7ac06cef MD	98	/*
	99	* This code section can only be included in LGPL 2.1 compatible source code.
	100	* See below for the function call wrappers which can be used in code meant to
	101	* be only linked with the Userspace RCU library. This comes with a small
	102	* performance degradation on the read-side due to the added function calls.
	103	* This is required to permit relinking with newer versions of the library.
	104	*/
	105
	106	/*
	107	* If a reader is really non-cooperative and refuses to commit its
4f8e3380	108	* urcu_reader.ctr count to memory (there is no barrier in the reader
7ac06cef MD	109	* per-se), kick it after a few loops waiting for it.
	110	*/
	111	#define KICK_READER_LOOPS 10000
	112
bc6c15bb MD	113	/*
	114	* Active attempts to check for reader Q.S. before calling futex().
	115	*/
	116	#define RCU_QS_ACTIVE_ATTEMPTS 100
	117
7ac06cef MD	118	#ifdef DEBUG_RCU
	119	#define rcu_assert(args...) assert(args)
	120	#else
	121	#define rcu_assert(args...)
	122	#endif
	123
	124	#ifdef DEBUG_YIELD
	125	#include <sched.h>
	126	#include <time.h>
	127	#include <pthread.h>
	128	#include <unistd.h>
	129
	130	#define YIELD_READ (1 << 0)
	131	#define YIELD_WRITE (1 << 1)
	132
	133	/* maximum sleep delay, in us */
	134	#define MAX_SLEEP 50
	135
	136	extern unsigned int yield_active;
	137	extern unsigned int __thread rand_yield;
	138
	139	static inline void debug_yield_read(void)
	140	{
	141	if (yield_active & YIELD_READ)
	142	if (rand_r(&rand_yield) & 0x1)
	143	usleep(rand_r(&rand_yield) % MAX_SLEEP);
	144	}
	145
	146	static inline void debug_yield_write(void)
	147	{
	148	if (yield_active & YIELD_WRITE)
	149	if (rand_r(&rand_yield) & 0x1)
	150	usleep(rand_r(&rand_yield) % MAX_SLEEP);
	151	}
	152
	153	static inline void debug_yield_init(void)
	154	{
	155	rand_yield = time(NULL) ^ pthread_self();
	156	}
	157	#else
	158	static inline void debug_yield_read(void)
	159	{
	160	}
	161
	162	static inline void debug_yield_write(void)
	163	{
	164	}
	165
	166	static inline void debug_yield_init(void)
	167	{
	168
	169	}
	170	#endif
	171
	172	static inline void reader_barrier()
	173	{
	174	smp_mb();
	175	}
	176
ac258107	177	#define RCU_GP_ONLINE (1UL << 0)
55570466	178	#define RCU_GP_CTR (1UL << 1)
ac258107	179
7ac06cef MD	180	/*
	181	* Global quiescent period counter with low-order bits unused.
	182	* Using a int rather than a char to eliminate false register dependencies
	183	* causing stalls on some architectures.
	184	*/
f0f7dbdd	185	extern unsigned long urcu_gp_ctr;
7ac06cef	186
4f8e3380	187	struct urcu_reader {
bd1a5e15	188	/* Data used by both reader and synchronize_rcu() */
4f8e3380	189	unsigned long ctr;
bd1a5e15 MD	190	/* Data used for registry */
bd1a5e15 MD	191	struct list_head head __attribute__((aligned(CACHE_LINE_SIZE)));
4f8e3380 MD	192	pthread_t tid;
	193	};
	194
	195	extern struct urcu_reader __thread urcu_reader;
7ac06cef	196
bc6c15bb MD	197	extern int gp_futex;
	198
	199	/*
	200	* Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
	201	*/
	202	static inline void wake_up_gp(void)
	203	{
ec4e58a3 MD	204	if (unlikely(uatomic_read(&gp_futex) == -1)) {
ec4e58a3 MD	205	uatomic_set(&gp_futex, 0);
bc6c15bb MD	206	futex(&gp_futex, FUTEX_WAKE, 1,
	207	NULL, NULL, 0);
	208	}
	209	}
	210
47d2f29e MD	211	#if (BITS_PER_LONG < 64)
	212	static inline int rcu_gp_ongoing(unsigned long *value)
	213	{
	214	unsigned long reader_gp;
	215
	216	if (value == NULL)
	217	return 0;
	218	reader_gp = LOAD_SHARED(*value);
	219	return reader_gp && ((reader_gp ^ urcu_gp_ctr) & RCU_GP_CTR);
	220	}
	221	#else /* !(BITS_PER_LONG < 64) */
f0f7dbdd	222	static inline int rcu_gp_ongoing(unsigned long *value)
7ac06cef	223	{
f0f7dbdd	224	unsigned long reader_gp;
4e560c17	225
7ac06cef MD	226	if (value == NULL)
7ac06cef MD	227	return 0;
4e560c17	228	reader_gp = LOAD_SHARED(*value);
f0f7dbdd	229	return reader_gp && (reader_gp - urcu_gp_ctr > ULONG_MAX / 2);
7ac06cef	230	}
47d2f29e	231	#endif /* !(BITS_PER_LONG < 64) */
7ac06cef MD	232
	233	static inline void _rcu_read_lock(void)
	234	{
4f8e3380	235	rcu_assert(urcu_reader.ctr);
7ac06cef MD	236	}
	237
	238	static inline void _rcu_read_unlock(void)
	239	{
	240	}
	241
	242	static inline void _rcu_quiescent_state(void)
	243	{
	244	smp_mb();
4f8e3380 MD	245	_STORE_SHARED(urcu_reader.ctr, _LOAD_SHARED(urcu_gp_ctr));
4f8e3380 MD	246	smp_mb(); /* write urcu_reader.ctr before read futex */
bc6c15bb	247	wake_up_gp();
7ac06cef MD	248	smp_mb();
	249	}
	250
	251	static inline void _rcu_thread_offline(void)
	252	{
	253	smp_mb();
4f8e3380 MD	254	STORE_SHARED(urcu_reader.ctr, 0);
4f8e3380 MD	255	smp_mb(); /* write urcu_reader.ctr before read futex */
bc6c15bb	256	wake_up_gp();
7ac06cef MD	257	}
	258
	259	static inline void _rcu_thread_online(void)
	260	{
4f8e3380	261	_STORE_SHARED(urcu_reader.ctr, LOAD_SHARED(urcu_gp_ctr));
7ac06cef MD	262	smp_mb();
	263	}
	264
	265	/**
	266	* _rcu_assign_pointer - assign (publicize) a pointer to a new data structure
	267	* meant to be read by RCU read-side critical sections. Returns the assigned
	268	* value.
	269	*
	270	* Documents which pointers will be dereferenced by RCU read-side critical
	271	* sections and adds the required memory barriers on architectures requiring
	272	* them. It also makes sure the compiler does not reorder code initializing the
	273	* data structure before its publication.
	274	*
	275	* Should match rcu_dereference_pointer().
	276	*/
	277
	278	#define _rcu_assign_pointer(p, v) \
	279	({ \
	280	if (!__builtin_constant_p(v) \|\| \
	281	((v) != NULL)) \
	282	wmb(); \
	283	STORE_SHARED(p, v); \
	284	})
	285
4d1ce26f MD	286	/**
	287	* _rcu_cmpxchg_pointer - same as rcu_assign_pointer, but tests if the pointer
	288	* is as expected by "old". If succeeds, returns the previous pointer to the
	289	* data structure, which can be safely freed after waiting for a quiescent state
	290	* using synchronize_rcu(). If fails (unexpected value), returns old (which
	291	* should not be freed !).
	292	*/
	293
	294	#define _rcu_cmpxchg_pointer(p, old, _new) \
	295	({ \
	296	if (!__builtin_constant_p(_new) \|\| \
	297	((_new) != NULL)) \
	298	wmb(); \
ec4e58a3	299	uatomic_cmpxchg(p, old, _new); \
4d1ce26f MD	300	})
4d1ce26f MD	301
7ac06cef MD	302	/**
	303	* _rcu_xchg_pointer - same as rcu_assign_pointer, but returns the previous
	304	* pointer to the data structure, which can be safely freed after waiting for a
	305	* quiescent state using synchronize_rcu().
	306	*/
	307
	308	#define _rcu_xchg_pointer(p, v) \
	309	({ \
	310	if (!__builtin_constant_p(v) \|\| \
	311	((v) != NULL)) \
	312	wmb(); \
ec4e58a3	313	uatomic_xchg(p, v); \
7ac06cef MD	314	})
	315
	316	/*
	317	* Exchanges the pointer and waits for quiescent state.
	318	* The pointer returned can be freed.
	319	*/
	320	#define _rcu_publish_content(p, v) \
	321	({ \
	322	void *oldptr; \
	323	oldptr = _rcu_xchg_pointer(p, v); \
	324	synchronize_rcu(); \
	325	oldptr; \
	326	})
	327
	328	#endif /* _URCU_QSBR_STATIC_H */