urcu: make the code of urcu-qsbr as normal urcu
[urcu.git] / urcu / static / urcu.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 CODE THAT IS TO BE RECOMPILED ON EACH LIBURCU
10 * RELEASE. See urcu.h for linking dynamically with the userspace rcu library.
adcfce54 11 *
6982d6d7 12 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
d2d23035 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>
bc6c15bb 34#include <unistd.h>
6d841bc2 35#include <stdint.h>
adcfce54 36
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37#include <urcu/compiler.h>
38#include <urcu/arch.h>
7e30abe3 39#include <urcu/system.h>
a2e7bf9c 40#include <urcu/uatomic.h>
e3b0cef0 41#include <urcu/list.h>
41849996 42#include <urcu/futex.h>
bd252a04 43#include <urcu/tls-compat.h>
bc6c15bb 44
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45#ifdef __cplusplus
46extern "C" {
47#endif
48
65f1e634 49/* Default is RCU_MEMBARRIER */
fdf01eed 50#if !defined(RCU_MEMBARRIER) && !defined(RCU_MB) && !defined(RCU_SIGNAL)
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51#define RCU_MEMBARRIER
52#endif
53
54/*
55 * RCU_MEMBARRIER is only possibly available on Linux. Fallback to RCU_MB
56 * otherwise.
57 */
58#if !defined(__linux__) && defined(RCU_MEMBARRIER)
59#undef RCU_MEMBARRIER
60#define RCU_MB
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61#endif
62
63#ifdef RCU_MEMBARRIER
4906d398 64#include <syscall.h>
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65
66/* If the headers do not support SYS_membarrier, statically use RCU_MB */
67#ifdef SYS_membarrier
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68# define MEMBARRIER_EXPEDITED (1 << 0)
69# define MEMBARRIER_DELAYED (1 << 1)
70# define MEMBARRIER_QUERY (1 << 16)
d4fc680a 71# define membarrier(...) syscall(SYS_membarrier, __VA_ARGS__)
fdf01eed 72#else
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73# undef RCU_MEMBARRIER
74# define RCU_MB
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75#endif
76#endif
77
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78/*
79 * This code section can only be included in LGPL 2.1 compatible source code.
80 * See below for the function call wrappers which can be used in code meant to
81 * be only linked with the Userspace RCU library. This comes with a small
82 * performance degradation on the read-side due to the added function calls.
83 * This is required to permit relinking with newer versions of the library.
84 */
85
86/*
87 * The signal number used by the RCU library can be overridden with
02be5561 88 * -DSIGRCU= when compiling the library.
ddf7eefb 89 * Provide backward compatibility for liburcu 0.3.x SIGURCU.
adcfce54 90 */
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91#ifdef SIGURCU
92#define SIGRCU SIGURCU
93#endif
94
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95#ifndef SIGRCU
96#define SIGRCU SIGUSR1
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97#endif
98
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99enum rcu_state {
100 RCU_READER_ACTIVE_CURRENT,
101 RCU_READER_ACTIVE_OLD,
102 RCU_READER_INACTIVE,
103};
104
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105#ifdef DEBUG_RCU
106#define rcu_assert(args...) assert(args)
107#else
108#define rcu_assert(args...)
109#endif
110
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111#ifdef DEBUG_YIELD
112#include <sched.h>
113#include <time.h>
114#include <pthread.h>
115#include <unistd.h>
116
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117#define RCU_YIELD_READ (1 << 0)
118#define RCU_YIELD_WRITE (1 << 1)
adcfce54 119
b4ce1526 120/*
fdf01eed 121 * Updates with RCU_SIGNAL are much slower. Account this in the delay.
b4ce1526 122 */
fdf01eed 123#ifdef RCU_SIGNAL
adcfce54 124/* maximum sleep delay, in us */
adcfce54 125#define MAX_SLEEP 30000
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126#else
127#define MAX_SLEEP 50
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128#endif
129
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130extern unsigned int rcu_yield_active;
131extern DECLARE_URCU_TLS(unsigned int, rcu_rand_yield);
adcfce54 132
1de4df4b 133static inline void rcu_debug_yield_read(void)
adcfce54 134{
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135 if (rcu_yield_active & RCU_YIELD_READ)
136 if (rand_r(&URCU_TLS(rcu_rand_yield)) & 0x1)
137 usleep(rand_r(&URCU_TLS(rcu_rand_yield)) % MAX_SLEEP);
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138}
139
1de4df4b 140static inline void rcu_debug_yield_write(void)
adcfce54 141{
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142 if (rcu_yield_active & RCU_YIELD_WRITE)
143 if (rand_r(&URCU_TLS(rcu_rand_yield)) & 0x1)
144 usleep(rand_r(&URCU_TLS(rcu_rand_yield)) % MAX_SLEEP);
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145}
146
1de4df4b 147static inline void rcu_debug_yield_init(void)
adcfce54 148{
1de4df4b 149 URCU_TLS(rcu_rand_yield) = time(NULL) ^ (unsigned long) pthread_self();
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150}
151#else
1de4df4b 152static inline void rcu_debug_yield_read(void)
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153{
154}
155
1de4df4b 156static inline void rcu_debug_yield_write(void)
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157{
158}
159
1de4df4b 160static inline void rcu_debug_yield_init(void)
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161{
162
163}
164#endif
165
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166/*
167 * RCU memory barrier broadcast group. Currently, only broadcast to all process
168 * threads is supported (group 0).
169 *
170 * Slave barriers are only guaranteed to be ordered wrt master barriers.
171 *
172 * The pair ordering is detailed as (O: ordered, X: not ordered) :
173 * slave master
174 * slave X O
175 * master O O
176 */
177
178#define MB_GROUP_ALL 0
179#define RCU_MB_GROUP MB_GROUP_ALL
180
fdf01eed 181#ifdef RCU_MEMBARRIER
1de4df4b 182extern int rcu_has_sys_membarrier;
fdf01eed 183
25cc6d18 184static inline void smp_mb_slave(int group)
fdf01eed 185{
1de4df4b 186 if (caa_likely(rcu_has_sys_membarrier))
5481ddb3 187 cmm_barrier();
fdf01eed 188 else
5481ddb3 189 cmm_smp_mb();
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190}
191#endif
192
02be5561 193#ifdef RCU_MB
25cc6d18 194static inline void smp_mb_slave(int group)
adcfce54 195{
5481ddb3 196 cmm_smp_mb();
adcfce54 197}
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198#endif
199
200#ifdef RCU_SIGNAL
25cc6d18 201static inline void smp_mb_slave(int group)
adcfce54 202{
5481ddb3 203 cmm_barrier();
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204}
205#endif
206
207/*
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208 * The trick here is that RCU_GP_CTR_PHASE must be a multiple of 8 so we can use
209 * a full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
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210 */
211#define RCU_GP_COUNT (1UL << 0)
212/* Use the amount of bits equal to half of the architecture long size */
27d65bc5 213#define RCU_GP_CTR_PHASE (1UL << (sizeof(unsigned long) << 2))
02be5561 214#define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_PHASE - 1)
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215
216/*
217 * Global quiescent period counter with low-order bits unused.
218 * Using a int rather than a char to eliminate false register dependencies
219 * causing stalls on some architectures.
220 */
27d65bc5 221extern unsigned long rcu_gp_ctr;
adcfce54 222
02be5561 223struct rcu_reader {
bd1a5e15 224 /* Data used by both reader and synchronize_rcu() */
27d65bc5 225 unsigned long ctr;
e3b0cef0 226 char need_mb;
bd1a5e15 227 /* Data used for registry */
16aa9ee8 228 struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
bd1a5e15 229 pthread_t tid;
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230};
231
bd252a04 232extern DECLARE_URCU_TLS(struct rcu_reader, rcu_reader);
adcfce54 233
1de4df4b 234extern int32_t rcu_gp_futex;
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235
236/*
237 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
238 */
239static inline void wake_up_gp(void)
240{
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241 if (caa_unlikely(uatomic_read(&rcu_gp_futex) == -1)) {
242 uatomic_set(&rcu_gp_futex, 0);
243 futex_async(&rcu_gp_futex, FUTEX_WAKE, 1,
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244 NULL, NULL, 0);
245 }
246}
247
fd189fa5 248static inline enum rcu_state rcu_reader_state(unsigned long *ctr)
adcfce54 249{
27d65bc5 250 unsigned long v;
adcfce54 251
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252 /*
253 * Make sure both tests below are done on the same version of *value
254 * to insure consistency.
255 */
6cf3827c 256 v = CMM_LOAD_SHARED(*ctr);
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257 if (!(v & RCU_GP_CTR_NEST_MASK))
258 return RCU_READER_INACTIVE;
259 if (!((v ^ rcu_gp_ctr) & RCU_GP_CTR_PHASE))
260 return RCU_READER_ACTIVE_CURRENT;
261 return RCU_READER_ACTIVE_OLD;
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262}
263
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264/*
265 * Helper for _rcu_read_lock(). The format of rcu_gp_ctr (as well as
266 * the per-thread rcu_reader.ctr) has the upper bits containing a count of
267 * _rcu_read_lock() nesting, and a lower-order bit that contains either zero
268 * or RCU_GP_CTR_PHASE. The smp_mb_slave() ensures that the accesses in
269 * _rcu_read_lock() happen before the subsequent read-side critical section.
270 */
271static inline void _rcu_read_lock_update(unsigned long tmp)
adcfce54 272{
a0b7f7ea 273 if (caa_likely(!(tmp & RCU_GP_CTR_NEST_MASK))) {
bd252a04 274 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, _CMM_LOAD_SHARED(rcu_gp_ctr));
25cc6d18 275 smp_mb_slave(RCU_MB_GROUP);
a5a9f428 276 } else
bd252a04 277 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, tmp + RCU_GP_COUNT);
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278}
279
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280/*
281 * Enter an RCU read-side critical section.
282 *
283 * The first cmm_barrier() call ensures that the compiler does not reorder
284 * the body of _rcu_read_lock() with a mutex.
285 *
286 * This function and its helper are both less than 10 lines long. The
287 * intent is that this function meets the 10-line criterion in LGPL,
288 * allowing this function to be invoked directly from non-LGPL code.
289 */
290static inline void _rcu_read_lock(void)
adcfce54 291{
27d65bc5 292 unsigned long tmp;
bc6c15bb 293
a5a9f428 294 cmm_barrier();
bd252a04 295 tmp = URCU_TLS(rcu_reader).ctr;
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296 _rcu_read_lock_update(tmp);
297}
298
299/*
300 * This is a helper function for _rcu_read_unlock().
301 *
302 * The first smp_mb_slave() call ensures that the critical section is
303 * seen to precede the store to rcu_reader.ctr.
304 * The second smp_mb_slave() call ensures that we write to rcu_reader.ctr
305 * before reading the update-side futex.
306 */
307static inline void _rcu_read_unlock_update_and_wakeup(unsigned long tmp)
308{
a0b7f7ea 309 if (caa_likely((tmp & RCU_GP_CTR_NEST_MASK) == RCU_GP_COUNT)) {
25cc6d18 310 smp_mb_slave(RCU_MB_GROUP);
bd252a04 311 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, URCU_TLS(rcu_reader).ctr - RCU_GP_COUNT);
25cc6d18 312 smp_mb_slave(RCU_MB_GROUP);
bc6c15bb 313 wake_up_gp();
a5a9f428 314 } else
bd252a04 315 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, URCU_TLS(rcu_reader).ctr - RCU_GP_COUNT);
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316}
317
318/*
319 * Exit an RCU read-side crtical section. Both this function and its
320 * helper are smaller than 10 lines of code, and are intended to be
321 * usable by non-LGPL code, as called out in LGPL.
322 */
323static inline void _rcu_read_unlock(void)
324{
325 unsigned long tmp;
326
327 tmp = URCU_TLS(rcu_reader).ctr;
328 _rcu_read_unlock_update_and_wakeup(tmp);
5481ddb3 329 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
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330}
331
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332/*
333 * Returns whether within a RCU read-side critical section.
334 *
335 * This function is less than 10 lines long. The intent is that this
336 * function meets the 10-line criterion for LGPL, allowing this function
337 * to be invoked directly from non-LGPL code.
338 */
339static inline int _rcu_read_ongoing(void)
340{
341 return URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK;
342}
343
ad918eeb 344#ifdef __cplusplus
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345}
346#endif
347
adcfce54 348#endif /* _URCU_STATIC_H */
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