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.
38 #include <urcu/debug.h>
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>
46 #include <urcu/static/urcu-common.h>
53 * This code section can only be included in LGPL 2.1 compatible source code.
54 * See below for the function call wrappers which can be used in code meant to
55 * be only linked with the Userspace RCU library. This comes with a small
56 * performance degradation on the read-side due to the added function calls.
57 * This is required to permit relinking with newer versions of the library.
60 #define URCU_QSBR_GP_ONLINE (1UL << 0)
61 #define URCU_QSBR_GP_CTR (1UL << 1)
63 extern struct urcu_gp urcu_qsbr_gp
;
65 struct urcu_qsbr_reader
{
66 /* Data used by both reader and synchronize_rcu() */
68 /* Data used for registry */
69 struct cds_list_head node
__attribute__((aligned(CAA_CACHE_LINE_SIZE
)));
72 /* Reader registered flag, for internal checks. */
73 unsigned int registered
:1;
76 extern DECLARE_URCU_TLS(struct urcu_qsbr_reader
, urcu_qsbr_reader
);
79 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
81 static inline void urcu_qsbr_wake_up_gp(void)
83 if (caa_unlikely(_CMM_LOAD_SHARED(URCU_TLS(urcu_qsbr_reader
).waiting
))) {
84 _CMM_STORE_SHARED(URCU_TLS(urcu_qsbr_reader
).waiting
, 0);
86 if (uatomic_read(&urcu_qsbr_gp
.futex
) != -1)
88 uatomic_set(&urcu_qsbr_gp
.futex
, 0);
90 * Ignoring return value until we can make this function
91 * return something (because urcu_die() is not publicly
94 (void) futex_noasync(&urcu_qsbr_gp
.futex
, FUTEX_WAKE
, 1,
99 static inline enum urcu_state
urcu_qsbr_reader_state(unsigned long *ctr
)
103 v
= CMM_LOAD_SHARED(*ctr
);
105 return URCU_READER_INACTIVE
;
106 if (v
== urcu_qsbr_gp
.ctr
)
107 return URCU_READER_ACTIVE_CURRENT
;
108 return URCU_READER_ACTIVE_OLD
;
112 * Enter an RCU read-side critical section.
114 * This function is less than 10 lines long. The intent is that this
115 * function meets the 10-line criterion for LGPL, allowing this function
116 * to be invoked directly from non-LGPL code.
118 static inline void _urcu_qsbr_read_lock(void)
120 urcu_assert_debug(URCU_TLS(urcu_qsbr_reader
).ctr
);
124 * Exit an RCU read-side critical section.
126 * This function is less than 10 lines long. The intent is that this
127 * function meets the 10-line criterion for LGPL, allowing this function
128 * to be invoked directly from non-LGPL code.
130 static inline void _urcu_qsbr_read_unlock(void)
132 urcu_assert_debug(URCU_TLS(urcu_qsbr_reader
).ctr
);
136 * Returns whether within a RCU read-side critical section.
138 * This function is less than 10 lines long. The intent is that this
139 * function meets the 10-line criterion for LGPL, allowing this function
140 * to be invoked directly from non-LGPL code.
142 static inline int _urcu_qsbr_read_ongoing(void)
144 return URCU_TLS(urcu_qsbr_reader
).ctr
;
148 * This is a helper function for _rcu_quiescent_state().
149 * The first cmm_smp_mb() ensures memory accesses in the prior read-side
150 * critical sections are not reordered with store to
151 * URCU_TLS(urcu_qsbr_reader).ctr, and ensures that mutexes held within an
152 * offline section that would happen to end with this
153 * urcu_qsbr_quiescent_state() call are not reordered with
154 * store to URCU_TLS(urcu_qsbr_reader).ctr.
156 static inline void _urcu_qsbr_quiescent_state_update_and_wakeup(unsigned long gp_ctr
)
159 _CMM_STORE_SHARED(URCU_TLS(urcu_qsbr_reader
).ctr
, gp_ctr
);
160 cmm_smp_mb(); /* write URCU_TLS(urcu_qsbr_reader).ctr before read futex */
161 urcu_qsbr_wake_up_gp();
166 * Inform RCU of a quiescent state.
168 * This function is less than 10 lines long. The intent is that this
169 * function meets the 10-line criterion for LGPL, allowing this function
170 * to be invoked directly from non-LGPL code.
172 * We skip the memory barriers and gp store if our local ctr already
173 * matches the global urcu_qsbr_gp.ctr value: this is OK because a prior
174 * _rcu_quiescent_state() or _rcu_thread_online() already updated it
175 * within our thread, so we have no quiescent state to report.
177 static inline void _urcu_qsbr_quiescent_state(void)
179 unsigned long gp_ctr
;
181 urcu_assert_debug(URCU_TLS(urcu_qsbr_reader
).registered
);
182 if ((gp_ctr
= CMM_LOAD_SHARED(urcu_qsbr_gp
.ctr
)) == URCU_TLS(urcu_qsbr_reader
).ctr
)
184 _urcu_qsbr_quiescent_state_update_and_wakeup(gp_ctr
);
188 * Take a thread offline, prohibiting it from entering further RCU
189 * read-side critical sections.
191 * This function is less than 10 lines long. The intent is that this
192 * function meets the 10-line criterion for LGPL, allowing this function
193 * to be invoked directly from non-LGPL code.
195 static inline void _urcu_qsbr_thread_offline(void)
197 urcu_assert_debug(URCU_TLS(urcu_qsbr_reader
).registered
);
199 CMM_STORE_SHARED(URCU_TLS(urcu_qsbr_reader
).ctr
, 0);
200 cmm_smp_mb(); /* write URCU_TLS(urcu_qsbr_reader).ctr before read futex */
201 urcu_qsbr_wake_up_gp();
202 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
206 * Bring a thread online, allowing it to once again enter RCU
207 * read-side critical sections.
209 * This function is less than 10 lines long. The intent is that this
210 * function meets the 10-line criterion for LGPL, allowing this function
211 * to be invoked directly from non-LGPL code.
213 static inline void _urcu_qsbr_thread_online(void)
215 urcu_assert_debug(URCU_TLS(urcu_qsbr_reader
).registered
);
216 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
217 _CMM_STORE_SHARED(URCU_TLS(urcu_qsbr_reader
).ctr
, CMM_LOAD_SHARED(urcu_qsbr_gp
.ctr
));
225 #endif /* _URCU_QSBR_STATIC_H */