Fix: handle sys_futex() FUTEX_WAIT interrupted by signal
[urcu.git] / urcu / static / urcu.h
1 #ifndef _URCU_STATIC_H
2 #define _URCU_STATIC_H
3
4 /*
5 * urcu-static.h
6 *
7 * Userspace RCU header.
8 *
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.
11 *
12 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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 <unistd.h>
35 #include <stdint.h>
36
37 #include <urcu/compiler.h>
38 #include <urcu/arch.h>
39 #include <urcu/system.h>
40 #include <urcu/uatomic.h>
41 #include <urcu/list.h>
42 #include <urcu/futex.h>
43 #include <urcu/tls-compat.h>
44 #include <urcu/rand-compat.h>
45
46 #ifdef __cplusplus
47 extern "C" {
48 #endif
49
50 /* Default is RCU_MEMBARRIER */
51 #if !defined(RCU_MEMBARRIER) && !defined(RCU_MB) && !defined(RCU_SIGNAL)
52 #define RCU_MEMBARRIER
53 #endif
54
55 /*
56 * This code section can only be included in LGPL 2.1 compatible source code.
57 * See below for the function call wrappers which can be used in code meant to
58 * be only linked with the Userspace RCU library. This comes with a small
59 * performance degradation on the read-side due to the added function calls.
60 * This is required to permit relinking with newer versions of the library.
61 */
62
63 /*
64 * The signal number used by the RCU library can be overridden with
65 * -DSIGRCU= when compiling the library.
66 * Provide backward compatibility for liburcu 0.3.x SIGURCU.
67 */
68 #ifdef SIGURCU
69 #define SIGRCU SIGURCU
70 #endif
71
72 #ifndef SIGRCU
73 #define SIGRCU SIGUSR1
74 #endif
75
76 enum rcu_state {
77 RCU_READER_ACTIVE_CURRENT,
78 RCU_READER_ACTIVE_OLD,
79 RCU_READER_INACTIVE,
80 };
81
82 #ifdef DEBUG_RCU
83 #define rcu_assert(args...) assert(args)
84 #else
85 #define rcu_assert(args...)
86 #endif
87
88 /*
89 * RCU memory barrier broadcast group. Currently, only broadcast to all process
90 * threads is supported (group 0).
91 *
92 * Slave barriers are only guaranteed to be ordered wrt master barriers.
93 *
94 * The pair ordering is detailed as (O: ordered, X: not ordered) :
95 * slave master
96 * slave X O
97 * master O O
98 */
99
100 #define MB_GROUP_ALL 0
101 #define RCU_MB_GROUP MB_GROUP_ALL
102
103 #ifdef RCU_MEMBARRIER
104 extern int rcu_has_sys_membarrier;
105
106 static inline void smp_mb_slave(int group)
107 {
108 if (caa_likely(rcu_has_sys_membarrier))
109 cmm_barrier();
110 else
111 cmm_smp_mb();
112 }
113 #endif
114
115 #ifdef RCU_MB
116 static inline void smp_mb_slave(int group)
117 {
118 cmm_smp_mb();
119 }
120 #endif
121
122 #ifdef RCU_SIGNAL
123 static inline void smp_mb_slave(int group)
124 {
125 cmm_barrier();
126 }
127 #endif
128
129 /*
130 * The trick here is that RCU_GP_CTR_PHASE must be a multiple of 8 so we can use
131 * a full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
132 */
133 #define RCU_GP_COUNT (1UL << 0)
134 /* Use the amount of bits equal to half of the architecture long size */
135 #define RCU_GP_CTR_PHASE (1UL << (sizeof(unsigned long) << 2))
136 #define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_PHASE - 1)
137
138 struct rcu_gp {
139 /*
140 * Global grace period counter.
141 * Contains the current RCU_GP_CTR_PHASE.
142 * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path.
143 * Written to only by writer with mutex taken.
144 * Read by both writer and readers.
145 */
146 unsigned long ctr;
147
148 int32_t futex;
149 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
150
151 extern struct rcu_gp rcu_gp;
152
153 struct rcu_reader {
154 /* Data used by both reader and synchronize_rcu() */
155 unsigned long ctr;
156 char need_mb;
157 /* Data used for registry */
158 struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
159 pthread_t tid;
160 };
161
162 extern DECLARE_URCU_TLS(struct rcu_reader, rcu_reader);
163
164 /*
165 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
166 */
167 static inline void wake_up_gp(void)
168 {
169 if (caa_unlikely(uatomic_read(&rcu_gp.futex) == -1)) {
170 uatomic_set(&rcu_gp.futex, 0);
171 /*
172 * Ignoring return value until we can make this function
173 * return something (because urcu_die() is not publicly
174 * exposed).
175 */
176 (void) futex_async(&rcu_gp.futex, FUTEX_WAKE, 1,
177 NULL, NULL, 0);
178 }
179 }
180
181 static inline enum rcu_state rcu_reader_state(unsigned long *ctr)
182 {
183 unsigned long v;
184
185 /*
186 * Make sure both tests below are done on the same version of *value
187 * to insure consistency.
188 */
189 v = CMM_LOAD_SHARED(*ctr);
190 if (!(v & RCU_GP_CTR_NEST_MASK))
191 return RCU_READER_INACTIVE;
192 if (!((v ^ rcu_gp.ctr) & RCU_GP_CTR_PHASE))
193 return RCU_READER_ACTIVE_CURRENT;
194 return RCU_READER_ACTIVE_OLD;
195 }
196
197 /*
198 * Helper for _rcu_read_lock(). The format of rcu_gp.ctr (as well as
199 * the per-thread rcu_reader.ctr) has the upper bits containing a count of
200 * _rcu_read_lock() nesting, and a lower-order bit that contains either zero
201 * or RCU_GP_CTR_PHASE. The smp_mb_slave() ensures that the accesses in
202 * _rcu_read_lock() happen before the subsequent read-side critical section.
203 */
204 static inline void _rcu_read_lock_update(unsigned long tmp)
205 {
206 if (caa_likely(!(tmp & RCU_GP_CTR_NEST_MASK))) {
207 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, _CMM_LOAD_SHARED(rcu_gp.ctr));
208 smp_mb_slave(RCU_MB_GROUP);
209 } else
210 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, tmp + RCU_GP_COUNT);
211 }
212
213 /*
214 * Enter an RCU read-side critical section.
215 *
216 * The first cmm_barrier() call ensures that the compiler does not reorder
217 * the body of _rcu_read_lock() with a mutex.
218 *
219 * This function and its helper are both less than 10 lines long. The
220 * intent is that this function meets the 10-line criterion in LGPL,
221 * allowing this function to be invoked directly from non-LGPL code.
222 */
223 static inline void _rcu_read_lock(void)
224 {
225 unsigned long tmp;
226
227 cmm_barrier();
228 tmp = URCU_TLS(rcu_reader).ctr;
229 _rcu_read_lock_update(tmp);
230 }
231
232 /*
233 * This is a helper function for _rcu_read_unlock().
234 *
235 * The first smp_mb_slave() call ensures that the critical section is
236 * seen to precede the store to rcu_reader.ctr.
237 * The second smp_mb_slave() call ensures that we write to rcu_reader.ctr
238 * before reading the update-side futex.
239 */
240 static inline void _rcu_read_unlock_update_and_wakeup(unsigned long tmp)
241 {
242 if (caa_likely((tmp & RCU_GP_CTR_NEST_MASK) == RCU_GP_COUNT)) {
243 smp_mb_slave(RCU_MB_GROUP);
244 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, URCU_TLS(rcu_reader).ctr - RCU_GP_COUNT);
245 smp_mb_slave(RCU_MB_GROUP);
246 wake_up_gp();
247 } else
248 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, URCU_TLS(rcu_reader).ctr - RCU_GP_COUNT);
249 }
250
251 /*
252 * Exit an RCU read-side crtical section. Both this function and its
253 * helper are smaller than 10 lines of code, and are intended to be
254 * usable by non-LGPL code, as called out in LGPL.
255 */
256 static inline void _rcu_read_unlock(void)
257 {
258 unsigned long tmp;
259
260 tmp = URCU_TLS(rcu_reader).ctr;
261 _rcu_read_unlock_update_and_wakeup(tmp);
262 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
263 }
264
265 /*
266 * Returns whether within a RCU read-side critical section.
267 *
268 * This function is less than 10 lines long. The intent is that this
269 * function meets the 10-line criterion for LGPL, allowing this function
270 * to be invoked directly from non-LGPL code.
271 */
272 static inline int _rcu_read_ongoing(void)
273 {
274 return URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK;
275 }
276
277 #ifdef __cplusplus
278 }
279 #endif
280
281 #endif /* _URCU_STATIC_H */
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