Fix some typos in PowerPC support code.
[urcu.git] / urcu-static.h
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1#ifndef _URCU_STATIC_H
2#define _URCU_STATIC_H
3
4/*
5 * urcu-static.h
6 *
d2d23035 7 * Userspace RCU header.
adcfce54 8 *
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9 * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu.h for linking
10 * dynamically with the userspace rcu library.
adcfce54 11 *
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12 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
13 * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
adcfce54 14 *
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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
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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
35#include <compiler.h>
36#include <arch.h>
37
38/*
39 * Identify a shared load. A smp_rmc() or smp_mc() should come before the load.
40 */
41#define _LOAD_SHARED(p) ACCESS_ONCE(p)
42
43/*
44 * Load a data from shared memory, doing a cache flush if required.
45 */
46#define LOAD_SHARED(p) \
47 ({ \
48 smp_rmc(); \
49 _LOAD_SHARED(p); \
50 })
51
52/*
53 * Identify a shared store. A smp_wmc() or smp_mc() should follow the store.
54 */
55#define _STORE_SHARED(x, v) ({ ACCESS_ONCE(x) = (v); })
56
57/*
58 * Store v into x, where x is located in shared memory. Performs the required
59 * cache flush after writing. Returns v.
60 */
61#define STORE_SHARED(x, v) \
62 ({ \
63 _STORE_SHARED(x, v); \
64 smp_wmc(); \
65 (v); \
66 })
67
68/**
69 * _rcu_dereference - reads (copy) a RCU-protected pointer to a local variable
70 * into a RCU read-side critical section. The pointer can later be safely
71 * dereferenced within the critical section.
72 *
73 * This ensures that the pointer copy is invariant thorough the whole critical
74 * section.
75 *
76 * Inserts memory barriers on architectures that require them (currently only
77 * Alpha) and documents which pointers are protected by RCU.
78 *
79 * Should match rcu_assign_pointer() or rcu_xchg_pointer().
80 */
81
82#define _rcu_dereference(p) ({ \
83 typeof(p) _________p1 = LOAD_SHARED(p); \
84 smp_read_barrier_depends(); \
85 (_________p1); \
86 })
87
88/*
89 * This code section can only be included in LGPL 2.1 compatible source code.
90 * See below for the function call wrappers which can be used in code meant to
91 * be only linked with the Userspace RCU library. This comes with a small
92 * performance degradation on the read-side due to the added function calls.
93 * This is required to permit relinking with newer versions of the library.
94 */
95
96/*
97 * The signal number used by the RCU library can be overridden with
98 * -DSIGURCU= when compiling the library.
99 */
100#ifndef SIGURCU
101#define SIGURCU SIGUSR1
102#endif
103
104/*
105 * If a reader is really non-cooperative and refuses to commit its
106 * urcu_active_readers count to memory (there is no barrier in the reader
107 * per-se), kick it after a few loops waiting for it.
108 */
109#define KICK_READER_LOOPS 10000
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/* Updates without DEBUG_FULL_MB are much slower. Account this in the delay */
121#ifdef DEBUG_FULL_MB
122/* maximum sleep delay, in us */
123#define MAX_SLEEP 50
124#else
125#define MAX_SLEEP 30000
126#endif
127
128extern unsigned int yield_active;
129extern unsigned int __thread rand_yield;
130
131static inline void debug_yield_read(void)
132{
133 if (yield_active & YIELD_READ)
134 if (rand_r(&rand_yield) & 0x1)
135 usleep(rand_r(&rand_yield) % MAX_SLEEP);
136}
137
138static inline void debug_yield_write(void)
139{
140 if (yield_active & YIELD_WRITE)
141 if (rand_r(&rand_yield) & 0x1)
142 usleep(rand_r(&rand_yield) % MAX_SLEEP);
143}
144
145static inline void debug_yield_init(void)
146{
147 rand_yield = time(NULL) ^ pthread_self();
148}
149#else
150static inline void debug_yield_read(void)
151{
152}
153
154static inline void debug_yield_write(void)
155{
156}
157
158static inline void debug_yield_init(void)
159{
160
161}
162#endif
163
164#ifdef DEBUG_FULL_MB
165static inline void reader_barrier()
166{
167 smp_mb();
168}
169#else
170static inline void reader_barrier()
171{
172 barrier();
173}
174#endif
175
176/*
177 * The trick here is that RCU_GP_CTR_BIT must be a multiple of 8 so we can use a
178 * full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
179 */
180#define RCU_GP_COUNT (1UL << 0)
181/* Use the amount of bits equal to half of the architecture long size */
182#define RCU_GP_CTR_BIT (1UL << (sizeof(long) << 2))
183#define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_BIT - 1)
184
185/*
186 * Global quiescent period counter with low-order bits unused.
187 * Using a int rather than a char to eliminate false register dependencies
188 * causing stalls on some architectures.
189 */
190extern long urcu_gp_ctr;
191
192extern long __thread urcu_active_readers;
193
194static inline int rcu_old_gp_ongoing(long *value)
195{
196 long v;
197
198 if (value == NULL)
199 return 0;
200 /*
201 * Make sure both tests below are done on the same version of *value
202 * to insure consistency.
203 */
204 v = LOAD_SHARED(*value);
205 return (v & RCU_GP_CTR_NEST_MASK) &&
206 ((v ^ urcu_gp_ctr) & RCU_GP_CTR_BIT);
207}
208
209static inline void _rcu_read_lock(void)
210{
211 long tmp;
212
213 tmp = urcu_active_readers;
214 /* urcu_gp_ctr = RCU_GP_COUNT | (~RCU_GP_CTR_BIT or RCU_GP_CTR_BIT) */
215 /*
216 * The data dependency "read urcu_gp_ctr, write urcu_active_readers",
217 * serializes those two memory operations. The memory barrier in the
218 * signal handler ensures we receive the proper memory commit barriers
219 * required by _STORE_SHARED and _LOAD_SHARED whenever communication
220 * with the writer is needed.
221 */
222 if (likely(!(tmp & RCU_GP_CTR_NEST_MASK)))
223 _STORE_SHARED(urcu_active_readers, _LOAD_SHARED(urcu_gp_ctr));
224 else
225 _STORE_SHARED(urcu_active_readers, tmp + RCU_GP_COUNT);
226 /*
227 * Increment active readers count before accessing the pointer.
228 * See force_mb_all_threads().
229 */
230 reader_barrier();
231}
232
233static inline void _rcu_read_unlock(void)
234{
235 reader_barrier();
236 /*
237 * Finish using rcu before decrementing the pointer.
238 * See force_mb_all_threads().
239 */
240 _STORE_SHARED(urcu_active_readers, urcu_active_readers - RCU_GP_COUNT);
241}
242
243/**
244 * _rcu_assign_pointer - assign (publicize) a pointer to a new data structure
245 * meant to be read by RCU read-side critical sections. Returns the assigned
246 * value.
247 *
248 * Documents which pointers will be dereferenced by RCU read-side critical
249 * sections and adds the required memory barriers on architectures requiring
250 * them. It also makes sure the compiler does not reorder code initializing the
251 * data structure before its publication.
252 *
253 * Should match rcu_dereference_pointer().
254 */
255
256#define _rcu_assign_pointer(p, v) \
257 ({ \
258 if (!__builtin_constant_p(v) || \
259 ((v) != NULL)) \
260 wmb(); \
261 STORE_SHARED(p, v); \
262 })
263
264/**
265 * _rcu_xchg_pointer - same as rcu_assign_pointer, but returns the previous
266 * pointer to the data structure, which can be safely freed after waitin for a
267 * quiescent state using synchronize_rcu().
268 */
269
270#define _rcu_xchg_pointer(p, v) \
271 ({ \
272 if (!__builtin_constant_p(v) || \
273 ((v) != NULL)) \
274 wmb(); \
275 xchg(p, v); \
276 })
277
278/*
279 * Exchanges the pointer and waits for quiescent state.
280 * The pointer returned can be freed.
281 */
282#define _rcu_publish_content(p, v) \
283 ({ \
284 void *oldptr; \
285 oldptr = _rcu_xchg_pointer(p, v); \
286 synchronize_rcu(); \
287 oldptr; \
288 })
289
290#endif /* _URCU_STATIC_H */
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