Cleanup: remove trailing whitespaces at EOL
[urcu.git] / urcu / static / urcu-bp.h
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1#ifndef _URCU_BP_STATIC_H
2#define _URCU_BP_STATIC_H
3
4/*
5 * urcu-bp-static.h
6 *
7 * Userspace RCU header.
8 *
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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.
fdee2e6d 11 *
6982d6d7 12 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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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>
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34#include <unistd.h>
35
36#include <urcu/compiler.h>
37#include <urcu/arch.h>
38#include <urcu/system.h>
a2e7bf9c 39#include <urcu/uatomic.h>
fdee2e6d 40#include <urcu/list.h>
bd252a04 41#include <urcu/tls-compat.h>
a77f7d82 42#include <urcu/debug.h>
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43
44/*
45 * This code section can only be included in LGPL 2.1 compatible source code.
46 * See below for the function call wrappers which can be used in code meant to
47 * be only linked with the Userspace RCU library. This comes with a small
48 * performance degradation on the read-side due to the added function calls.
49 * This is required to permit relinking with newer versions of the library.
50 */
51
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52#ifdef __cplusplus
53extern "C" {
54#endif
55
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56enum rcu_state {
57 RCU_READER_ACTIVE_CURRENT,
58 RCU_READER_ACTIVE_OLD,
59 RCU_READER_INACTIVE,
60};
61
fdee2e6d 62/*
02be5561 63 * The trick here is that RCU_GP_CTR_PHASE must be a multiple of 8 so we can use a
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64 * full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
65 */
66#define RCU_GP_COUNT (1UL << 0)
67/* Use the amount of bits equal to half of the architecture long size */
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68#define RCU_GP_CTR_PHASE (1UL << (sizeof(long) << 2))
69#define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_PHASE - 1)
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70
71/*
72 * Used internally by _rcu_read_lock.
73 */
74extern void rcu_bp_register(void);
75
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76struct rcu_gp {
77 /*
78 * Global grace period counter.
79 * Contains the current RCU_GP_CTR_PHASE.
80 * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path.
81 * Written to only by writer with mutex taken.
82 * Read by both writer and readers.
83 */
84 unsigned long ctr;
85} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
86
87extern struct rcu_gp rcu_gp;
fdee2e6d 88
02be5561 89struct rcu_reader {
fdee2e6d 90 /* Data used by both reader and synchronize_rcu() */
52c75091 91 unsigned long ctr;
fdee2e6d 92 /* Data used for registry */
16aa9ee8 93 struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
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94 pthread_t tid;
95 int alloc; /* registry entry allocated */
96};
97
98/*
99 * Bulletproof version keeps a pointer to a registry not part of the TLS.
100 * Adds a pointer dereference on the read-side, but won't require to unregister
101 * the reader thread.
102 */
bd252a04 103extern DECLARE_URCU_TLS(struct rcu_reader *, rcu_reader);
fdee2e6d 104
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105extern int urcu_bp_has_sys_membarrier;
106
107static inline void urcu_bp_smp_mb_slave(void)
108{
109 if (caa_likely(urcu_bp_has_sys_membarrier))
110 cmm_barrier();
111 else
112 cmm_smp_mb();
113}
114
52c75091 115static inline enum rcu_state rcu_reader_state(unsigned long *ctr)
fdee2e6d 116{
52c75091 117 unsigned long v;
fdee2e6d 118
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119 if (ctr == NULL)
120 return RCU_READER_INACTIVE;
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121 /*
122 * Make sure both tests below are done on the same version of *value
123 * to insure consistency.
124 */
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125 v = CMM_LOAD_SHARED(*ctr);
126 if (!(v & RCU_GP_CTR_NEST_MASK))
127 return RCU_READER_INACTIVE;
c13c2e55 128 if (!((v ^ rcu_gp.ctr) & RCU_GP_CTR_PHASE))
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129 return RCU_READER_ACTIVE_CURRENT;
130 return RCU_READER_ACTIVE_OLD;
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131}
132
a5a9f428 133/*
c13c2e55 134 * Helper for _rcu_read_lock(). The format of rcu_gp.ctr (as well as
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135 * the per-thread rcu_reader.ctr) has the upper bits containing a count of
136 * _rcu_read_lock() nesting, and a lower-order bit that contains either zero
137 * or RCU_GP_CTR_PHASE. The smp_mb_slave() ensures that the accesses in
138 * _rcu_read_lock() happen before the subsequent read-side critical section.
139 */
140static inline void _rcu_read_lock_update(unsigned long tmp)
141{
142 if (caa_likely(!(tmp & RCU_GP_CTR_NEST_MASK))) {
c13c2e55 143 _CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, _CMM_LOAD_SHARED(rcu_gp.ctr));
f541831e 144 urcu_bp_smp_mb_slave();
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145 } else
146 _CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, tmp + RCU_GP_COUNT);
147}
148
149/*
150 * Enter an RCU read-side critical section.
151 *
152 * The first cmm_barrier() call ensures that the compiler does not reorder
153 * the body of _rcu_read_lock() with a mutex.
154 *
155 * This function and its helper are both less than 10 lines long. The
156 * intent is that this function meets the 10-line criterion in LGPL,
157 * allowing this function to be invoked directly from non-LGPL code.
158 */
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159static inline void _rcu_read_lock(void)
160{
52c75091 161 unsigned long tmp;
fdee2e6d 162
bd252a04 163 if (caa_unlikely(!URCU_TLS(rcu_reader)))
a5a9f428 164 rcu_bp_register(); /* If not yet registered. */
5481ddb3 165 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
bd252a04 166 tmp = URCU_TLS(rcu_reader)->ctr;
6ef5ddc9 167 urcu_assert((tmp & RCU_GP_CTR_NEST_MASK) != RCU_GP_CTR_NEST_MASK);
a5a9f428 168 _rcu_read_lock_update(tmp);
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169}
170
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171/*
172 * Exit an RCU read-side critical section. This function is less than
173 * 10 lines of code, and is intended to be usable by non-LGPL code, as
174 * called out in LGPL.
175 */
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176static inline void _rcu_read_unlock(void)
177{
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178 unsigned long tmp;
179
180 tmp = URCU_TLS(rcu_reader)->ctr;
181 urcu_assert(tmp & RCU_GP_CTR_NEST_MASK);
182 /* Finish using rcu before decrementing the pointer. */
f541831e 183 urcu_bp_smp_mb_slave();
343c8b13 184 _CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, tmp - RCU_GP_COUNT);
5481ddb3 185 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
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186}
187
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188/*
189 * Returns whether within a RCU read-side critical section.
190 *
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.
194 */
195static inline int _rcu_read_ongoing(void)
196{
197 if (caa_unlikely(!URCU_TLS(rcu_reader)))
198 rcu_bp_register(); /* If not yet registered. */
199 return URCU_TLS(rcu_reader)->ctr & RCU_GP_CTR_NEST_MASK;
200}
201
67ecffc0 202#ifdef __cplusplus
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203}
204#endif
205
fdee2e6d 206#endif /* _URCU_BP_STATIC_H */
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