1 #ifndef _URCU_QSBR_STATIC_H
2 #define _URCU_QSBR_STATIC_H
7 * Userspace RCU QSBR header.
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.
12 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
13 * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
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.
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.
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
29 * IBM's contributions to this file may be relicensed under LGPLv2 or later.
39 #include <urcu/compiler.h>
40 #include <urcu/arch.h>
41 #include <urcu/system.h>
42 #include <urcu/uatomic.h>
43 #include <urcu/list.h>
44 #include <urcu/futex.h>
45 #include <urcu/tls-compat.h>
52 * This code section can only be included in LGPL 2.1 compatible source code.
53 * See below for the function call wrappers which can be used in code meant to
54 * be only linked with the Userspace RCU library. This comes with a small
55 * performance degradation on the read-side due to the added function calls.
56 * This is required to permit relinking with newer versions of the library.
60 #define rcu_assert(args...) assert(args)
62 #define rcu_assert(args...)
66 RCU_READER_ACTIVE_CURRENT
,
67 RCU_READER_ACTIVE_OLD
,
77 #define RCU_YIELD_READ (1 << 0)
78 #define RCU_YIELD_WRITE (1 << 1)
80 /* maximum sleep delay, in us */
83 extern unsigned int rcu_yield_active
;
84 extern DECLARE_URCU_TLS(unsigned int, rcu_rand_yield
);
86 static inline void rcu_debug_yield_read(void)
88 if (rcu_yield_active
& RCU_YIELD_READ
)
89 if (rand_r(&URCU_TLS(rcu_rand_yield
)) & 0x1)
90 usleep(rand_r(&URCU_TLS(rcu_rand_yield
)) % MAX_SLEEP
);
93 static inline void rcu_debug_yield_write(void)
95 if (rcu_yield_active
& RCU_YIELD_WRITE
)
96 if (rand_r(&URCU_TLS(rcu_rand_yield
)) & 0x1)
97 usleep(rand_r(&URCU_TLS(rcu_rand_yield
)) % MAX_SLEEP
);
100 static inline void rcu_debug_yield_init(void)
102 URCU_TLS(rcu_rand_yield
) = time(NULL
) ^ (unsigned long) pthread_self();
105 static inline void rcu_debug_yield_read(void)
109 static inline void rcu_debug_yield_write(void)
113 static inline void rcu_debug_yield_init(void)
119 #define RCU_GP_ONLINE (1UL << 0)
120 #define RCU_GP_CTR (1UL << 1)
123 * Global quiescent period counter with low-order bits unused.
124 * Using a int rather than a char to eliminate false register dependencies
125 * causing stalls on some architectures.
127 extern unsigned long rcu_gp_ctr
;
130 /* Data used by both reader and synchronize_rcu() */
132 /* Data used for registry */
133 struct cds_list_head node
__attribute__((aligned(CAA_CACHE_LINE_SIZE
)));
138 extern DECLARE_URCU_TLS(struct rcu_reader
, rcu_reader
);
140 extern int32_t rcu_gp_futex
;
143 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
145 static inline void wake_up_gp(void)
147 if (caa_unlikely(_CMM_LOAD_SHARED(URCU_TLS(rcu_reader
).waiting
))) {
148 _CMM_STORE_SHARED(URCU_TLS(rcu_reader
).waiting
, 0);
150 if (uatomic_read(&rcu_gp_futex
) != -1)
152 uatomic_set(&rcu_gp_futex
, 0);
153 futex_noasync(&rcu_gp_futex
, FUTEX_WAKE
, 1,
158 static inline enum rcu_state
rcu_reader_state(unsigned long *ctr
)
162 v
= CMM_LOAD_SHARED(*ctr
);
164 return RCU_READER_INACTIVE
;
166 return RCU_READER_ACTIVE_CURRENT
;
167 return RCU_READER_ACTIVE_OLD
;
171 * Enter an RCU read-side critical section.
173 * This function is less than 10 lines long. The intent is that this
174 * function meets the 10-line criterion for LGPL, allowing this function
175 * to be invoked directly from non-LGPL code.
177 static inline void _rcu_read_lock(void)
179 rcu_assert(URCU_TLS(rcu_reader
).ctr
);
183 * Exit an RCU read-side critical section.
185 * This function is less than 10 lines long. The intent is that this
186 * function meets the 10-line criterion for LGPL, allowing this function
187 * to be invoked directly from non-LGPL code.
189 static inline void _rcu_read_unlock(void)
194 * Returns whether within a RCU read-side critical section.
196 * This function is less than 10 lines long. The intent is that this
197 * function meets the 10-line criterion for LGPL, allowing this function
198 * to be invoked directly from non-LGPL code.
200 static inline int _rcu_read_ongoing(void)
202 return URCU_TLS(rcu_reader
).ctr
;
206 * This is a helper function for _rcu_quiescent_state().
207 * The first cmm_smp_mb() ensures memory accesses in the prior read-side
208 * critical sections are not reordered with store to
209 * URCU_TLS(rcu_reader).ctr, and ensures that mutexes held within an
210 * offline section that would happen to end with this
211 * rcu_quiescent_state() call are not reordered with
212 * store to URCU_TLS(rcu_reader).ctr.
214 static inline void _rcu_quiescent_state_update_and_wakeup(unsigned long gp_ctr
)
217 _CMM_STORE_SHARED(URCU_TLS(rcu_reader
).ctr
, gp_ctr
);
218 cmm_smp_mb(); /* write URCU_TLS(rcu_reader).ctr before read futex */
224 * Inform RCU of a quiescent state.
226 * This function is less than 10 lines long. The intent is that this
227 * function meets the 10-line criterion for LGPL, allowing this function
228 * to be invoked directly from non-LGPL code.
230 * We skip the memory barriers and gp store if our local ctr already
231 * matches the global rcu_gp_ctr value: this is OK because a prior
232 * _rcu_quiescent_state() or _rcu_thread_online() already updated it
233 * within our thread, so we have no quiescent state to report.
235 static inline void _rcu_quiescent_state(void)
237 unsigned long gp_ctr
;
239 if ((gp_ctr
= CMM_LOAD_SHARED(rcu_gp_ctr
)) == URCU_TLS(rcu_reader
).ctr
)
241 _rcu_quiescent_state_update_and_wakeup(gp_ctr
);
245 * Take a thread offline, prohibiting it from entering further RCU
246 * read-side critical sections.
248 * This function is less than 10 lines long. The intent is that this
249 * function meets the 10-line criterion for LGPL, allowing this function
250 * to be invoked directly from non-LGPL code.
252 static inline void _rcu_thread_offline(void)
255 CMM_STORE_SHARED(URCU_TLS(rcu_reader
).ctr
, 0);
256 cmm_smp_mb(); /* write URCU_TLS(rcu_reader).ctr before read futex */
258 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
262 * Bring a thread online, allowing it to once again enter RCU
263 * read-side critical sections.
265 * This function is less than 10 lines long. The intent is that this
266 * function meets the 10-line criterion for LGPL, allowing this function
267 * to be invoked directly from non-LGPL code.
269 static inline void _rcu_thread_online(void)
271 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
272 _CMM_STORE_SHARED(URCU_TLS(rcu_reader
).ctr
, CMM_LOAD_SHARED(rcu_gp_ctr
));
280 #endif /* _URCU_QSBR_STATIC_H */