urcu qsbr: add DEBUG_RCU self check
[urcu.git] / urcu-qsbr.h
CommitLineData
420e5b92
MD
1#ifndef _URCU_QSBR_H
2#define _URCU_QSBR_H
3
4/*
5 * urcu-static.h
6 *
7 * Userspace RCU header.
8 *
9 * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu.h for linking
10 * dynamically with the userspace rcu 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>
fb6e510b 34#include <assert.h>
420e5b92
MD
35
36#include <compiler.h>
37#include <arch.h>
38
39/*
40 * Identify a shared load. A smp_rmc() or smp_mc() should come before the load.
41 */
42#define _LOAD_SHARED(p) ACCESS_ONCE(p)
43
44/*
45 * Load a data from shared memory, doing a cache flush if required.
46 */
47#define LOAD_SHARED(p) \
48 ({ \
49 smp_rmc(); \
50 _LOAD_SHARED(p); \
51 })
52
53/*
54 * Identify a shared store. A smp_wmc() or smp_mc() should follow the store.
55 */
56#define _STORE_SHARED(x, v) ({ ACCESS_ONCE(x) = (v); })
57
58/*
59 * Store v into x, where x is located in shared memory. Performs the required
60 * cache flush after writing. Returns v.
61 */
62#define STORE_SHARED(x, v) \
63 ({ \
64 _STORE_SHARED(x, v); \
65 smp_wmc(); \
66 (v); \
67 })
68
69/**
70 * _rcu_dereference - reads (copy) a RCU-protected pointer to a local variable
71 * into a RCU read-side critical section. The pointer can later be safely
72 * dereferenced within the critical section.
73 *
74 * This ensures that the pointer copy is invariant thorough the whole critical
75 * section.
76 *
77 * Inserts memory barriers on architectures that require them (currently only
78 * Alpha) and documents which pointers are protected by RCU.
79 *
80 * Should match rcu_assign_pointer() or rcu_xchg_pointer().
81 */
82
83#define _rcu_dereference(p) ({ \
84 typeof(p) _________p1 = LOAD_SHARED(p); \
85 smp_read_barrier_depends(); \
86 (_________p1); \
87 })
88
89/*
90 * This code section can only be included in LGPL 2.1 compatible source code.
91 * See below for the function call wrappers which can be used in code meant to
92 * be only linked with the Userspace RCU library. This comes with a small
93 * performance degradation on the read-side due to the added function calls.
94 * This is required to permit relinking with newer versions of the library.
95 */
96
97/*
98 * The signal number used by the RCU library can be overridden with
99 * -DSIGURCU= when compiling the library.
100 */
101#ifndef SIGURCU
102#define SIGURCU SIGUSR1
103#endif
104
105/*
106 * If a reader is really non-cooperative and refuses to commit its
3395d46c 107 * rcu_reader_qs_gp count to memory (there is no barrier in the reader
420e5b92
MD
108 * per-se), kick it after a few loops waiting for it.
109 */
110#define KICK_READER_LOOPS 10000
111
fb6e510b
MD
112#ifdef DEBUG_RCU
113#define rcu_assert(args...) assert(args)
114#else
115#define rcu_assert(args...)
116#endif
117
420e5b92
MD
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
420e5b92
MD
127/* maximum sleep delay, in us */
128#define MAX_SLEEP 50
420e5b92
MD
129
130extern unsigned int yield_active;
131extern unsigned int __thread rand_yield;
132
133static 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
140static 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
147static inline void debug_yield_init(void)
148{
149 rand_yield = time(NULL) ^ pthread_self();
150}
151#else
152static inline void debug_yield_read(void)
153{
154}
155
156static inline void debug_yield_write(void)
157{
158}
159
160static inline void debug_yield_init(void)
161{
162
163}
164#endif
165
420e5b92
MD
166static inline void reader_barrier()
167{
168 smp_mb();
169}
420e5b92 170
420e5b92
MD
171/*
172 * Global quiescent period counter with low-order bits unused.
173 * Using a int rather than a char to eliminate false register dependencies
174 * causing stalls on some architectures.
175 */
176extern long urcu_gp_ctr;
177
3395d46c 178extern long __thread rcu_reader_qs_gp;
420e5b92 179
3395d46c 180static inline int rcu_gp_ongoing(long *value)
420e5b92
MD
181{
182 if (value == NULL)
183 return 0;
184
185 return LOAD_SHARED(*value) & 1;
186}
187
188static inline void _rcu_read_lock(void)
189{
fb6e510b 190 rcu_assert(rcu_reader_qs_gp & 1);
420e5b92
MD
191}
192
193static inline void _rcu_read_unlock(void)
194{
195}
196
197static inline void _rcu_quiescent_state(void)
198{
199 smp_mb();
3395d46c 200 rcu_reader_qs_gp = ACCESS_ONCE(urcu_gp_ctr) + 1;
420e5b92
MD
201 smp_mb();
202}
203
204static inline void _rcu_thread_offline(void)
205{
206 smp_mb();
3395d46c 207 rcu_reader_qs_gp = ACCESS_ONCE(urcu_gp_ctr);
420e5b92
MD
208}
209
210static inline void _rcu_thread_online(void)
211{
3395d46c 212 rcu_reader_qs_gp = ACCESS_ONCE(urcu_gp_ctr) + 1;
420e5b92
MD
213 smp_mb();
214}
215
216/**
217 * _rcu_assign_pointer - assign (publicize) a pointer to a new data structure
218 * meant to be read by RCU read-side critical sections. Returns the assigned
219 * value.
220 *
221 * Documents which pointers will be dereferenced by RCU read-side critical
222 * sections and adds the required memory barriers on architectures requiring
223 * them. It also makes sure the compiler does not reorder code initializing the
224 * data structure before its publication.
225 *
226 * Should match rcu_dereference_pointer().
227 */
228
229#define _rcu_assign_pointer(p, v) \
230 ({ \
231 if (!__builtin_constant_p(v) || \
232 ((v) != NULL)) \
233 wmb(); \
234 STORE_SHARED(p, v); \
235 })
236
237/**
238 * _rcu_xchg_pointer - same as rcu_assign_pointer, but returns the previous
239 * pointer to the data structure, which can be safely freed after waiting for a
240 * quiescent state using synchronize_rcu().
241 */
242
243#define _rcu_xchg_pointer(p, v) \
244 ({ \
245 if (!__builtin_constant_p(v) || \
246 ((v) != NULL)) \
247 wmb(); \
248 xchg(p, v); \
249 })
250
251/*
252 * Exchanges the pointer and waits for quiescent state.
253 * The pointer returned can be freed.
254 */
255#define _rcu_publish_content(p, v) \
256 ({ \
257 void *oldptr; \
258 oldptr = _rcu_xchg_pointer(p, v); \
259 synchronize_rcu(); \
260 oldptr; \
261 })
262
263extern void synchronize_rcu(void);
264
265/*
266 * Reader thread registration.
267 */
268extern void rcu_register_thread(void);
269extern void rcu_unregister_thread(void);
270
271#endif /* _URCU_QSBR_H */
This page took 0.049471 seconds and 4 git commands to generate.