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[urcu.git] / urcu-qsbr-static.h
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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>
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36
37#include <compiler.h>
38#include <arch.h>
39
40/*
41 * Identify a shared load. A smp_rmc() or smp_mc() should come before the load.
42 */
43#define _LOAD_SHARED(p) ACCESS_ONCE(p)
44
45/*
46 * Load a data from shared memory, doing a cache flush if required.
47 */
48#define LOAD_SHARED(p) \
49 ({ \
50 smp_rmc(); \
51 _LOAD_SHARED(p); \
52 })
53
54/*
55 * Identify a shared store. A smp_wmc() or smp_mc() should follow the store.
56 */
57#define _STORE_SHARED(x, v) ({ ACCESS_ONCE(x) = (v); })
58
59/*
60 * Store v into x, where x is located in shared memory. Performs the required
61 * cache flush after writing. Returns v.
62 */
63#define STORE_SHARED(x, v) \
64 ({ \
65 _STORE_SHARED(x, v); \
66 smp_wmc(); \
67 (v); \
68 })
69
70/**
71 * _rcu_dereference - reads (copy) a RCU-protected pointer to a local variable
72 * into a RCU read-side critical section. The pointer can later be safely
73 * dereferenced within the critical section.
74 *
75 * This ensures that the pointer copy is invariant thorough the whole critical
76 * section.
77 *
78 * Inserts memory barriers on architectures that require them (currently only
79 * Alpha) and documents which pointers are protected by RCU.
80 *
81 * Should match rcu_assign_pointer() or rcu_xchg_pointer().
82 */
83
84#define _rcu_dereference(p) ({ \
85 typeof(p) _________p1 = LOAD_SHARED(p); \
86 smp_read_barrier_depends(); \
87 (_________p1); \
88 })
89
90/*
91 * This code section can only be included in LGPL 2.1 compatible source code.
92 * See below for the function call wrappers which can be used in code meant to
93 * be only linked with the Userspace RCU library. This comes with a small
94 * performance degradation on the read-side due to the added function calls.
95 * This is required to permit relinking with newer versions of the library.
96 */
97
98/*
99 * If a reader is really non-cooperative and refuses to commit its
100 * rcu_reader_qs_gp count to memory (there is no barrier in the reader
101 * per-se), kick it after a few loops waiting for it.
102 */
103#define KICK_READER_LOOPS 10000
104
105#ifdef DEBUG_RCU
106#define rcu_assert(args...) assert(args)
107#else
108#define rcu_assert(args...)
109#endif
110
111#ifdef DEBUG_YIELD
112#include <sched.h>
113#include <time.h>
114#include <pthread.h>
115#include <unistd.h>
116
117#define YIELD_READ (1 << 0)
118#define YIELD_WRITE (1 << 1)
119
120/* maximum sleep delay, in us */
121#define MAX_SLEEP 50
122
123extern unsigned int yield_active;
124extern unsigned int __thread rand_yield;
125
126static inline void debug_yield_read(void)
127{
128 if (yield_active & YIELD_READ)
129 if (rand_r(&rand_yield) & 0x1)
130 usleep(rand_r(&rand_yield) % MAX_SLEEP);
131}
132
133static inline void debug_yield_write(void)
134{
135 if (yield_active & YIELD_WRITE)
136 if (rand_r(&rand_yield) & 0x1)
137 usleep(rand_r(&rand_yield) % MAX_SLEEP);
138}
139
140static inline void debug_yield_init(void)
141{
142 rand_yield = time(NULL) ^ pthread_self();
143}
144#else
145static inline void debug_yield_read(void)
146{
147}
148
149static inline void debug_yield_write(void)
150{
151}
152
153static inline void debug_yield_init(void)
154{
155
156}
157#endif
158
159static inline void reader_barrier()
160{
161 smp_mb();
162}
163
ac258107 164#define RCU_GP_ONLINE (1UL << 0)
55570466 165#define RCU_GP_CTR (1UL << 1)
ac258107 166
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167/*
168 * Global quiescent period counter with low-order bits unused.
169 * Using a int rather than a char to eliminate false register dependencies
170 * causing stalls on some architectures.
171 */
f0f7dbdd 172extern unsigned long urcu_gp_ctr;
7ac06cef 173
f0f7dbdd 174extern unsigned long __thread rcu_reader_qs_gp;
7ac06cef 175
f0f7dbdd 176static inline int rcu_gp_ongoing(unsigned long *value)
7ac06cef 177{
f0f7dbdd 178 unsigned long reader_gp;
4e560c17 179
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180 if (value == NULL)
181 return 0;
4e560c17 182 reader_gp = LOAD_SHARED(*value);
f0f7dbdd 183 return reader_gp && (reader_gp - urcu_gp_ctr > ULONG_MAX / 2);
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184}
185
186static inline void _rcu_read_lock(void)
187{
ac258107 188 rcu_assert(rcu_reader_qs_gp);
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189}
190
191static inline void _rcu_read_unlock(void)
192{
193}
194
195static inline void _rcu_quiescent_state(void)
196{
197 smp_mb();
ab179a17 198 _STORE_SHARED(rcu_reader_qs_gp, _LOAD_SHARED(urcu_gp_ctr));
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199 smp_mb();
200}
201
202static inline void _rcu_thread_offline(void)
203{
204 smp_mb();
4e560c17 205 STORE_SHARED(rcu_reader_qs_gp, 0);
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206}
207
208static inline void _rcu_thread_online(void)
209{
ab179a17 210 _STORE_SHARED(rcu_reader_qs_gp, LOAD_SHARED(urcu_gp_ctr));
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211 smp_mb();
212}
213
214/**
215 * _rcu_assign_pointer - assign (publicize) a pointer to a new data structure
216 * meant to be read by RCU read-side critical sections. Returns the assigned
217 * value.
218 *
219 * Documents which pointers will be dereferenced by RCU read-side critical
220 * sections and adds the required memory barriers on architectures requiring
221 * them. It also makes sure the compiler does not reorder code initializing the
222 * data structure before its publication.
223 *
224 * Should match rcu_dereference_pointer().
225 */
226
227#define _rcu_assign_pointer(p, v) \
228 ({ \
229 if (!__builtin_constant_p(v) || \
230 ((v) != NULL)) \
231 wmb(); \
232 STORE_SHARED(p, v); \
233 })
234
235/**
236 * _rcu_xchg_pointer - same as rcu_assign_pointer, but returns the previous
237 * pointer to the data structure, which can be safely freed after waiting for a
238 * quiescent state using synchronize_rcu().
239 */
240
241#define _rcu_xchg_pointer(p, v) \
242 ({ \
243 if (!__builtin_constant_p(v) || \
244 ((v) != NULL)) \
245 wmb(); \
246 xchg(p, v); \
247 })
248
249/*
250 * Exchanges the pointer and waits for quiescent state.
251 * The pointer returned can be freed.
252 */
253#define _rcu_publish_content(p, v) \
254 ({ \
255 void *oldptr; \
256 oldptr = _rcu_xchg_pointer(p, v); \
257 synchronize_rcu(); \
258 oldptr; \
259 })
260
261#endif /* _URCU_QSBR_STATIC_H */
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