4de6da00c7112c7d5e1b542497ab436d673f9048
[urcu.git] / include / urcu / static / urcu-signal.h
1 #ifndef _URCU_SIGNAL_STATIC_H
2 #define _URCU_SIGNAL_STATIC_H
3
4 /*
5 * urcu-signal-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/config.h>
38 #include <urcu/compiler.h>
39 #include <urcu/arch.h>
40 #include <urcu/system.h>
41 #include <urcu/uatomic.h>
42 #include <urcu/list.h>
43 #include <urcu/futex.h>
44 #include <urcu/tls-compat.h>
45 #include <urcu/debug.h>
46 #include <urcu/static/urcu-common.h>
47 #include <urcu/static/urcu-signal-nr.h>
48
49 #ifdef __cplusplus
50 extern "C" {
51 #endif
52
53 /*
54 * This code section can only be included in LGPL 2.1 compatible source code.
55 * See below for the function call wrappers which can be used in code meant to
56 * be only linked with the Userspace RCU library. This comes with a small
57 * performance degradation on the read-side due to the added function calls.
58 * This is required to permit relinking with newer versions of the library.
59 */
60
61 extern struct urcu_gp urcu_signal_gp;
62
63 extern DECLARE_URCU_TLS(struct urcu_reader, urcu_signal_reader);
64
65 /*
66 * Helper for _rcu_read_lock(). The format of urcu_signal_gp.ctr (as well as
67 * the per-thread rcu_reader.ctr) has the upper bits containing a count of
68 * _rcu_read_lock() nesting, and a lower-order bit that contains either zero
69 * or URCU_GP_CTR_PHASE. The cmm_barrier() ensures that the accesses in
70 * _rcu_read_lock() happen before the subsequent read-side critical section.
71 */
72 static inline void _urcu_signal_read_lock_update(unsigned long tmp)
73 {
74 if (caa_likely(!(tmp & URCU_GP_CTR_NEST_MASK))) {
75 _CMM_STORE_SHARED(URCU_TLS(urcu_signal_reader).ctr, _CMM_LOAD_SHARED(urcu_signal_gp.ctr));
76 cmm_barrier();
77 } else
78 _CMM_STORE_SHARED(URCU_TLS(urcu_signal_reader).ctr, tmp + URCU_GP_COUNT);
79 }
80
81 /*
82 * Enter an RCU read-side critical section.
83 *
84 * The first cmm_barrier() call ensures that the compiler does not reorder
85 * the body of _rcu_read_lock() with a mutex.
86 *
87 * This function and its helper are both less than 10 lines long. The
88 * intent is that this function meets the 10-line criterion in LGPL,
89 * allowing this function to be invoked directly from non-LGPL code.
90 */
91 static inline void _urcu_signal_read_lock(void)
92 {
93 unsigned long tmp;
94
95 urcu_assert(URCU_TLS(urcu_signal_reader).registered);
96 cmm_barrier();
97 tmp = URCU_TLS(urcu_signal_reader).ctr;
98 urcu_assert((tmp & URCU_GP_CTR_NEST_MASK) != URCU_GP_CTR_NEST_MASK);
99 _urcu_signal_read_lock_update(tmp);
100 }
101
102 /*
103 * This is a helper function for _rcu_read_unlock().
104 *
105 * The first cmm_barrier() call ensures that the critical section is
106 * seen to precede the store to rcu_reader.ctr.
107 * The second cmm_barrier() call ensures that we write to rcu_reader.ctr
108 * before reading the update-side futex.
109 */
110 static inline void _urcu_signal_read_unlock_update_and_wakeup(unsigned long tmp)
111 {
112 if (caa_likely((tmp & URCU_GP_CTR_NEST_MASK) == URCU_GP_COUNT)) {
113 cmm_barrier();
114 _CMM_STORE_SHARED(URCU_TLS(urcu_signal_reader).ctr, tmp - URCU_GP_COUNT);
115 cmm_barrier();
116 urcu_common_wake_up_gp(&urcu_signal_gp);
117 } else
118 _CMM_STORE_SHARED(URCU_TLS(urcu_signal_reader).ctr, tmp - URCU_GP_COUNT);
119 }
120
121 /*
122 * Exit an RCU read-side critical section. Both this function and its
123 * helper are smaller than 10 lines of code, and are intended to be
124 * usable by non-LGPL code, as called out in LGPL.
125 */
126 static inline void _urcu_signal_read_unlock(void)
127 {
128 unsigned long tmp;
129
130 urcu_assert(URCU_TLS(urcu_signal_reader).registered);
131 tmp = URCU_TLS(urcu_signal_reader).ctr;
132 urcu_assert(tmp & URCU_GP_CTR_NEST_MASK);
133 _urcu_signal_read_unlock_update_and_wakeup(tmp);
134 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
135 }
136
137 /*
138 * Returns whether within a RCU read-side critical section.
139 *
140 * This function is less than 10 lines long. The intent is that this
141 * function meets the 10-line criterion for LGPL, allowing this function
142 * to be invoked directly from non-LGPL code.
143 */
144 static inline int _urcu_signal_read_ongoing(void)
145 {
146 return URCU_TLS(urcu_signal_reader).ctr & URCU_GP_CTR_NEST_MASK;
147 }
148
149 #ifdef __cplusplus
150 }
151 #endif
152
153 #endif /* _URCU_SIGNAL_STATIC_H */
This page took 0.04542 seconds and 3 git commands to generate.