Refactor liburcu to support many flavors per compile unit
[urcu.git] / include / urcu / static / urcu-signal.h
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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
48#ifdef __cplusplus
49extern "C" {
50#endif
51
52/*
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.
58 */
59
60/*
61 * The signal number used by the RCU library can be overridden with
62 * -DSIGRCU= when compiling the library.
63 * Provide backward compatibility for liburcu 0.3.x SIGURCU.
64 */
65#ifdef SIGURCU
66#define SIGRCU SIGURCU
67#endif
68
69#ifndef SIGRCU
70#define SIGRCU SIGUSR1
71#endif
72
73extern struct urcu_gp urcu_signal_gp;
74
75extern DECLARE_URCU_TLS(struct urcu_reader, urcu_signal_reader);
76
77/*
78 * Helper for _rcu_read_lock(). The format of urcu_signal_gp.ctr (as well as
79 * the per-thread rcu_reader.ctr) has the upper bits containing a count of
80 * _rcu_read_lock() nesting, and a lower-order bit that contains either zero
81 * or URCU_GP_CTR_PHASE. The cmm_barrier() ensures that the accesses in
82 * _rcu_read_lock() happen before the subsequent read-side critical section.
83 */
84static inline void _urcu_signal_read_lock_update(unsigned long tmp)
85{
86 if (caa_likely(!(tmp & URCU_GP_CTR_NEST_MASK))) {
87 _CMM_STORE_SHARED(URCU_TLS(urcu_signal_reader).ctr, _CMM_LOAD_SHARED(urcu_signal_gp.ctr));
88 cmm_barrier();
89 } else
90 _CMM_STORE_SHARED(URCU_TLS(urcu_signal_reader).ctr, tmp + URCU_GP_COUNT);
91}
92
93/*
94 * Enter an RCU read-side critical section.
95 *
96 * The first cmm_barrier() call ensures that the compiler does not reorder
97 * the body of _rcu_read_lock() with a mutex.
98 *
99 * This function and its helper are both less than 10 lines long. The
100 * intent is that this function meets the 10-line criterion in LGPL,
101 * allowing this function to be invoked directly from non-LGPL code.
102 */
103static inline void _urcu_signal_read_lock(void)
104{
105 unsigned long tmp;
106
107 urcu_assert(URCU_TLS(urcu_signal_reader).registered);
108 cmm_barrier();
109 tmp = URCU_TLS(urcu_signal_reader).ctr;
110 urcu_assert((tmp & URCU_GP_CTR_NEST_MASK) != URCU_GP_CTR_NEST_MASK);
111 _urcu_signal_read_lock_update(tmp);
112}
113
114/*
115 * This is a helper function for _rcu_read_unlock().
116 *
117 * The first cmm_barrier() call ensures that the critical section is
118 * seen to precede the store to rcu_reader.ctr.
119 * The second cmm_barrier() call ensures that we write to rcu_reader.ctr
120 * before reading the update-side futex.
121 */
122static inline void _urcu_signal_read_unlock_update_and_wakeup(unsigned long tmp)
123{
124 if (caa_likely((tmp & URCU_GP_CTR_NEST_MASK) == URCU_GP_COUNT)) {
125 cmm_barrier();
126 _CMM_STORE_SHARED(URCU_TLS(urcu_signal_reader).ctr, tmp - URCU_GP_COUNT);
127 cmm_barrier();
128 urcu_common_wake_up_gp(&urcu_signal_gp);
129 } else
130 _CMM_STORE_SHARED(URCU_TLS(urcu_signal_reader).ctr, tmp - URCU_GP_COUNT);
131}
132
133/*
134 * Exit an RCU read-side crtical section. Both this function and its
135 * helper are smaller than 10 lines of code, and are intended to be
136 * usable by non-LGPL code, as called out in LGPL.
137 */
138static inline void _urcu_signal_read_unlock(void)
139{
140 unsigned long tmp;
141
142 urcu_assert(URCU_TLS(urcu_signal_reader).registered);
143 tmp = URCU_TLS(urcu_signal_reader).ctr;
144 urcu_assert(tmp & URCU_GP_CTR_NEST_MASK);
145 _urcu_signal_read_unlock_update_and_wakeup(tmp);
146 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
147}
148
149/*
150 * Returns whether within a RCU read-side critical section.
151 *
152 * This function is less than 10 lines long. The intent is that this
153 * function meets the 10-line criterion for LGPL, allowing this function
154 * to be invoked directly from non-LGPL code.
155 */
156static inline int _urcu_signal_read_ongoing(void)
157{
158 return URCU_TLS(urcu_signal_reader).ctr & URCU_GP_CTR_NEST_MASK;
159}
160
161#ifdef __cplusplus
162}
163#endif
164
165#endif /* _URCU_SIGNAL_STATIC_H */
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