[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 <sys/time.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;
	unsigned long qs_time_delta_usec;
	struct timeval qs_time_last;
};

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;
	struct timeval current_time, delta_time;

	smp_mb();
	gettimeofday(&current_time, NULL);
	timersub(&current_time, &urcu_reader_status.qs_time_last, &delta_time);
	if (delta_time.tv_sec >= 1)
		_STORE_SHARED(urcu_reader_status.qs_time_delta_usec, 1000000);
	else
		_STORE_SHARED(urcu_reader_status.qs_time_delta_usec,
		      (unsigned long)delta_time.tv_usec);
	urcu_reader_status.qs_time_last = current_time;
	/*
	 * 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);
	if (unlikely(LOAD_SHARED(urcu_gp_ctr) & RCU_GP_ONGOING) &&
	    unlikely(urcu_reader_status.gp_waiting)) {
		sched_yield();
	}
}

static inline void _rcu_thread_online(void)
{
	struct timeval current_time, delta_time;

	gettimeofday(&current_time, NULL);
	timersub(&current_time, &urcu_reader_status.qs_time_last, &delta_time);
	if (delta_time.tv_sec >= 1)
		_STORE_SHARED(urcu_reader_status.qs_time_delta_usec, 1000000);
	else
		_STORE_SHARED(urcu_reader_status.qs_time_delta_usec,
		      (unsigned long)delta_time.tv_usec);
	urcu_reader_status.qs_time_last = current_time;
	_STORE_SHARED(urcu_reader_status.qs_time_delta_usec, 0);
	_STORE_SHARED(urcu_reader_status.qs_gp, 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();				\
		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>
ee72ef6e	37	#include <sys/time.h>
7ac06cef MD	38
	39	#include <compiler.h>
	40	#include <arch.h>
	41
	42	/*
	43	* Identify a shared load. A smp_rmc() or smp_mc() should come before the load.
	44	*/
	45	#define _LOAD_SHARED(p) ACCESS_ONCE(p)
	46
	47	/*
	48	* Load a data from shared memory, doing a cache flush if required.
	49	*/
	50	#define LOAD_SHARED(p) \
	51	({ \
	52	smp_rmc(); \
	53	_LOAD_SHARED(p); \
	54	})
	55
	56	/*
	57	* Identify a shared store. A smp_wmc() or smp_mc() should follow the store.
	58	*/
	59	#define _STORE_SHARED(x, v) ({ ACCESS_ONCE(x) = (v); })
	60
	61	/*
	62	* Store v into x, where x is located in shared memory. Performs the required
	63	* cache flush after writing. Returns v.
	64	*/
	65	#define STORE_SHARED(x, v) \
	66	({ \
	67	_STORE_SHARED(x, v); \
	68	smp_wmc(); \
	69	(v); \
	70	})
	71
	72	/**
	73	* _rcu_dereference - reads (copy) a RCU-protected pointer to a local variable
	74	* into a RCU read-side critical section. The pointer can later be safely
	75	* dereferenced within the critical section.
	76	*
	77	* This ensures that the pointer copy is invariant thorough the whole critical
	78	* section.
	79	*
	80	* Inserts memory barriers on architectures that require them (currently only
	81	* Alpha) and documents which pointers are protected by RCU.
	82	*
	83	* Should match rcu_assign_pointer() or rcu_xchg_pointer().
	84	*/
	85
	86	#define _rcu_dereference(p) ({ \
	87	typeof(p) _________p1 = LOAD_SHARED(p); \
	88	smp_read_barrier_depends(); \
	89	(_________p1); \
	90	})
	91
	92	/*
	93	* This code section can only be included in LGPL 2.1 compatible source code.
	94	* See below for the function call wrappers which can be used in code meant to
	95	* be only linked with the Userspace RCU library. This comes with a small
	96	* performance degradation on the read-side due to the added function calls.
	97	* This is required to permit relinking with newer versions of the library.
	98	*/
	99
	100	/*
	101	* If a reader is really non-cooperative and refuses to commit its
8b25e300	102	* rcu_reader qs_gp count to memory (there is no barrier in the reader
7ac06cef MD	103	* per-se), kick it after a few loops waiting for it.
	104	*/
	105	#define KICK_READER_LOOPS 10000
	106
bc6c15bb	107	/*
ae62b5e8	108	* Active attempts to check for reader Q.S. before calling sched_yield().
bc6c15bb MD	109	*/
	110	#define RCU_QS_ACTIVE_ATTEMPTS 100
	111
7ac06cef MD	112	#ifdef DEBUG_RCU
	113	#define rcu_assert(args...) assert(args)
	114	#else
	115	#define rcu_assert(args...)
	116	#endif
	117
	118	#ifdef DEBUG_YIELD
	119	#include <sched.h>
	120	#include <time.h>
	121	#include <pthread.h>
	122	#include <unistd.h>
	123
	124	#define YIELD_READ (1 << 0)
	125	#define YIELD_WRITE (1 << 1)
	126
	127	/* maximum sleep delay, in us */
	128	#define MAX_SLEEP 50
	129
	130	extern unsigned int yield_active;
	131	extern unsigned int __thread rand_yield;
	132
	133	static inline void debug_yield_read(void)
	134	{
	135	if (yield_active & YIELD_READ)
	136	if (rand_r(&rand_yield) & 0x1)
	137	usleep(rand_r(&rand_yield) % MAX_SLEEP);
	138	}
	139
	140	static inline void debug_yield_write(void)
	141	{
	142	if (yield_active & YIELD_WRITE)
	143	if (rand_r(&rand_yield) & 0x1)
	144	usleep(rand_r(&rand_yield) % MAX_SLEEP);
	145	}
	146
	147	static inline void debug_yield_init(void)
	148	{
	149	rand_yield = time(NULL) ^ pthread_self();
	150	}
	151	#else
	152	static inline void debug_yield_read(void)
	153	{
	154	}
	155
	156	static inline void debug_yield_write(void)
	157	{
	158	}
	159
	160	static inline void debug_yield_init(void)
	161	{
	162
	163	}
	164	#endif
	165
	166	static inline void reader_barrier()
	167	{
	168	smp_mb();
	169	}
	170
ac258107	171	#define RCU_GP_ONLINE (1UL << 0)
ae62b5e8 MD	172	#define RCU_GP_ONGOING (1UL << 1)
ae62b5e8 MD	173	#define RCU_GP_CTR (1UL << 2)
ac258107	174
7ac06cef MD	175	/*
	176	* Global quiescent period counter with low-order bits unused.
	177	* Using a int rather than a char to eliminate false register dependencies
	178	* causing stalls on some architectures.
	179	*/
f0f7dbdd	180	extern unsigned long urcu_gp_ctr;
7ac06cef	181
8b25e300 MD	182	struct urcu_reader_status {
	183	unsigned long qs_gp;
	184	unsigned long gp_waiting;
ee72ef6e MD	185	unsigned long qs_time_delta_usec;
ee72ef6e MD	186	struct timeval qs_time_last;
8b25e300 MD	187	};
	188
	189	extern struct urcu_reader_status __thread urcu_reader_status;
7ac06cef	190
47d2f29e MD	191	#if (BITS_PER_LONG < 64)
	192	static inline int rcu_gp_ongoing(unsigned long *value)
	193	{
	194	unsigned long reader_gp;
	195
	196	if (value == NULL)
	197	return 0;
	198	reader_gp = LOAD_SHARED(*value);
	199	return reader_gp && ((reader_gp ^ urcu_gp_ctr) & RCU_GP_CTR);
	200	}
	201	#else /* !(BITS_PER_LONG < 64) */
f0f7dbdd	202	static inline int rcu_gp_ongoing(unsigned long *value)
7ac06cef	203	{
f0f7dbdd	204	unsigned long reader_gp;
4e560c17	205
7ac06cef MD	206	if (value == NULL)
7ac06cef MD	207	return 0;
4e560c17	208	reader_gp = LOAD_SHARED(*value);
f0f7dbdd	209	return reader_gp && (reader_gp - urcu_gp_ctr > ULONG_MAX / 2);
7ac06cef	210	}
47d2f29e	211	#endif /* !(BITS_PER_LONG < 64) */
7ac06cef MD	212
	213	static inline void _rcu_read_lock(void)
	214	{
8b25e300	215	rcu_assert(urcu_reader_status.qs_gp);
7ac06cef MD	216	}
	217
	218	static inline void _rcu_read_unlock(void)
	219	{
	220	}
	221
	222	static inline void _rcu_quiescent_state(void)
	223	{
ae62b5e8	224	long gp_ctr;
539718ae	225	struct timeval current_time, delta_time;
ae62b5e8 MD	226
ae62b5e8 MD	227	smp_mb();
ee72ef6e	228	gettimeofday(&current_time, NULL);
539718ae MD	229	timersub(&current_time, &urcu_reader_status.qs_time_last, &delta_time);
539718ae MD	230	if (delta_time.tv_sec >= 1)
ee72ef6e MD	231	_STORE_SHARED(urcu_reader_status.qs_time_delta_usec, 1000000);
	232	else
	233	_STORE_SHARED(urcu_reader_status.qs_time_delta_usec,
539718ae	234	(unsigned long)delta_time.tv_usec);
ee72ef6e	235	urcu_reader_status.qs_time_last = current_time;
8b25e300 MD	236	/*
	237	* volatile accesses can be reordered by the compiler when put in the
	238	* same expression.
	239	*/
	240	if (unlikely((gp_ctr = LOAD_SHARED(urcu_gp_ctr)) & RCU_GP_ONGOING) &&
	241	unlikely(urcu_reader_status.gp_waiting)) {
	242	_STORE_SHARED(urcu_reader_status.qs_gp, gp_ctr);
ae62b5e8	243	sched_yield();
8b25e300 MD	244	} else {
8b25e300 MD	245	_STORE_SHARED(urcu_reader_status.qs_gp, gp_ctr);
ae62b5e8	246	}
7ac06cef MD	247	smp_mb();
	248	}
	249
	250	static inline void _rcu_thread_offline(void)
	251	{
	252	smp_mb();
8b25e300	253	STORE_SHARED(urcu_reader_status.qs_gp, 0);
b3c4dd1a MD	254	if (unlikely(LOAD_SHARED(urcu_gp_ctr) & RCU_GP_ONGOING) &&
	255	unlikely(urcu_reader_status.gp_waiting)) {
	256	sched_yield();
	257	}
7ac06cef MD	258	}
	259
	260	static inline void _rcu_thread_online(void)
	261	{
539718ae	262	struct timeval current_time, delta_time;
ee72ef6e MD	263
ee72ef6e MD	264	gettimeofday(&current_time, NULL);
539718ae MD	265	timersub(&current_time, &urcu_reader_status.qs_time_last, &delta_time);
539718ae MD	266	if (delta_time.tv_sec >= 1)
ee72ef6e MD	267	_STORE_SHARED(urcu_reader_status.qs_time_delta_usec, 1000000);
	268	else
	269	_STORE_SHARED(urcu_reader_status.qs_time_delta_usec,
539718ae	270	(unsigned long)delta_time.tv_usec);
ee72ef6e MD	271	urcu_reader_status.qs_time_last = current_time;
ee72ef6e MD	272	_STORE_SHARED(urcu_reader_status.qs_time_delta_usec, 0);
b3c4dd1a	273	_STORE_SHARED(urcu_reader_status.qs_gp, LOAD_SHARED(urcu_gp_ctr));
7ac06cef MD	274	smp_mb();
	275	}
	276
	277	/**
	278	* _rcu_assign_pointer - assign (publicize) a pointer to a new data structure
	279	* meant to be read by RCU read-side critical sections. Returns the assigned
	280	* value.
	281	*
	282	* Documents which pointers will be dereferenced by RCU read-side critical
	283	* sections and adds the required memory barriers on architectures requiring
	284	* them. It also makes sure the compiler does not reorder code initializing the
	285	* data structure before its publication.
	286	*
	287	* Should match rcu_dereference_pointer().
	288	*/
	289
	290	#define _rcu_assign_pointer(p, v) \
	291	({ \
	292	if (!__builtin_constant_p(v) \|\| \
	293	((v) != NULL)) \
	294	wmb(); \
	295	STORE_SHARED(p, v); \
	296	})
	297
4d1ce26f MD	298	/**
	299	* _rcu_cmpxchg_pointer - same as rcu_assign_pointer, but tests if the pointer
	300	* is as expected by "old". If succeeds, returns the previous pointer to the
	301	* data structure, which can be safely freed after waiting for a quiescent state
	302	* using synchronize_rcu(). If fails (unexpected value), returns old (which
	303	* should not be freed !).
	304	*/
	305
	306	#define _rcu_cmpxchg_pointer(p, old, _new) \
	307	({ \
	308	if (!__builtin_constant_p(_new) \|\| \
	309	((_new) != NULL)) \
	310	wmb(); \
	311	cmpxchg(p, old, _new); \
	312	})
	313
7ac06cef MD	314	/**
	315	* _rcu_xchg_pointer - same as rcu_assign_pointer, but returns the previous
	316	* pointer to the data structure, which can be safely freed after waiting for a
	317	* quiescent state using synchronize_rcu().
	318	*/
	319
	320	#define _rcu_xchg_pointer(p, v) \
	321	({ \
	322	if (!__builtin_constant_p(v) \|\| \
	323	((v) != NULL)) \
	324	wmb(); \
	325	xchg(p, v); \
	326	})
	327
	328	/*
	329	* Exchanges the pointer and waits for quiescent state.
	330	* The pointer returned can be freed.
	331	*/
	332	#define _rcu_publish_content(p, v) \
	333	({ \
	334	void *oldptr; \
	335	oldptr = _rcu_xchg_pointer(p, v); \
	336	synchronize_rcu(); \
	337	oldptr; \
	338	})
	339
	340	#endif /* _URCU_QSBR_STATIC_H */