wfstack: implement cds_wfs_pop_all and iterators, document API
[urcu.git] / urcu / static / urcu-bp.h
CommitLineData
fdee2e6d
MD
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 *
a5a9f428
PM
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>
fdee2e6d
MD
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>
fdee2e6d
MD
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>
fdee2e6d
MD
42
43/*
44 * This code section can only be included in LGPL 2.1 compatible source code.
45 * See below for the function call wrappers which can be used in code meant to
46 * be only linked with the Userspace RCU library. This comes with a small
47 * performance degradation on the read-side due to the added function calls.
48 * This is required to permit relinking with newer versions of the library.
49 */
50
36bc70a8
MD
51#ifdef __cplusplus
52extern "C" {
53#endif
54
fdee2e6d
MD
55#ifdef DEBUG_RCU
56#define rcu_assert(args...) assert(args)
57#else
58#define rcu_assert(args...)
59#endif
60
61#ifdef DEBUG_YIELD
62#include <sched.h>
63#include <time.h>
64#include <pthread.h>
65#include <unistd.h>
66
67#define YIELD_READ (1 << 0)
68#define YIELD_WRITE (1 << 1)
69
70/*
02be5561 71 * Updates without RCU_MB are much slower. Account this in
fdee2e6d
MD
72 * the delay.
73 */
74/* maximum sleep delay, in us */
75#define MAX_SLEEP 50
76
77extern unsigned int yield_active;
bd252a04 78extern DECLARE_URCU_TLS(unsigned int, rand_yield);
fdee2e6d
MD
79
80static inline void debug_yield_read(void)
81{
82 if (yield_active & YIELD_READ)
bd252a04
MD
83 if (rand_r(&URCU_TLS(rand_yield)) & 0x1)
84 usleep(rand_r(&URCU_TLS(rand_yield)) % MAX_SLEEP);
fdee2e6d
MD
85}
86
87static inline void debug_yield_write(void)
88{
89 if (yield_active & YIELD_WRITE)
bd252a04
MD
90 if (rand_r(&URCU_TLS(rand_yield)) & 0x1)
91 usleep(rand_r(&URCU_TLS(rand_yield)) % MAX_SLEEP);
fdee2e6d
MD
92}
93
94static inline void debug_yield_init(void)
95{
bd252a04 96 URCU_TLS(rand_yield) = time(NULL) ^ pthread_self();
fdee2e6d
MD
97}
98#else
99static inline void debug_yield_read(void)
100{
101}
102
103static inline void debug_yield_write(void)
104{
105}
106
107static inline void debug_yield_init(void)
108{
109
110}
111#endif
112
113/*
02be5561 114 * The trick here is that RCU_GP_CTR_PHASE must be a multiple of 8 so we can use a
fdee2e6d
MD
115 * full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
116 */
117#define RCU_GP_COUNT (1UL << 0)
118/* Use the amount of bits equal to half of the architecture long size */
02be5561
MD
119#define RCU_GP_CTR_PHASE (1UL << (sizeof(long) << 2))
120#define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_PHASE - 1)
fdee2e6d
MD
121
122/*
123 * Used internally by _rcu_read_lock.
124 */
125extern void rcu_bp_register(void);
126
127/*
128 * Global quiescent period counter with low-order bits unused.
129 * Using a int rather than a char to eliminate false register dependencies
130 * causing stalls on some architectures.
131 */
02be5561 132extern long rcu_gp_ctr;
fdee2e6d 133
02be5561 134struct rcu_reader {
fdee2e6d
MD
135 /* Data used by both reader and synchronize_rcu() */
136 long ctr;
137 /* Data used for registry */
16aa9ee8 138 struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
fdee2e6d
MD
139 pthread_t tid;
140 int alloc; /* registry entry allocated */
141};
142
143/*
144 * Bulletproof version keeps a pointer to a registry not part of the TLS.
145 * Adds a pointer dereference on the read-side, but won't require to unregister
146 * the reader thread.
147 */
bd252a04 148extern DECLARE_URCU_TLS(struct rcu_reader *, rcu_reader);
fdee2e6d
MD
149
150static inline int rcu_old_gp_ongoing(long *value)
151{
152 long v;
153
154 if (value == NULL)
155 return 0;
156 /*
157 * Make sure both tests below are done on the same version of *value
158 * to insure consistency.
159 */
6cf3827c 160 v = CMM_LOAD_SHARED(*value);
fdee2e6d 161 return (v & RCU_GP_CTR_NEST_MASK) &&
02be5561 162 ((v ^ rcu_gp_ctr) & RCU_GP_CTR_PHASE);
fdee2e6d
MD
163}
164
a5a9f428
PM
165/*
166 * Helper for _rcu_read_lock(). The format of rcu_gp_ctr (as well as
167 * the per-thread rcu_reader.ctr) has the upper bits containing a count of
168 * _rcu_read_lock() nesting, and a lower-order bit that contains either zero
169 * or RCU_GP_CTR_PHASE. The smp_mb_slave() ensures that the accesses in
170 * _rcu_read_lock() happen before the subsequent read-side critical section.
171 */
172static inline void _rcu_read_lock_update(unsigned long tmp)
173{
174 if (caa_likely(!(tmp & RCU_GP_CTR_NEST_MASK))) {
175 _CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, _CMM_LOAD_SHARED(rcu_gp_ctr));
176 cmm_smp_mb();
177 } else
178 _CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, tmp + RCU_GP_COUNT);
179}
180
181/*
182 * Enter an RCU read-side critical section.
183 *
184 * The first cmm_barrier() call ensures that the compiler does not reorder
185 * the body of _rcu_read_lock() with a mutex.
186 *
187 * This function and its helper are both less than 10 lines long. The
188 * intent is that this function meets the 10-line criterion in LGPL,
189 * allowing this function to be invoked directly from non-LGPL code.
190 */
fdee2e6d
MD
191static inline void _rcu_read_lock(void)
192{
193 long tmp;
194
bd252a04 195 if (caa_unlikely(!URCU_TLS(rcu_reader)))
a5a9f428 196 rcu_bp_register(); /* If not yet registered. */
5481ddb3 197 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
bd252a04 198 tmp = URCU_TLS(rcu_reader)->ctr;
a5a9f428 199 _rcu_read_lock_update(tmp);
fdee2e6d
MD
200}
201
a5a9f428
PM
202/*
203 * Exit an RCU read-side critical section. This function is less than
204 * 10 lines of code, and is intended to be usable by non-LGPL code, as
205 * called out in LGPL.
206 */
fdee2e6d
MD
207static inline void _rcu_read_unlock(void)
208{
209 /*
210 * Finish using rcu before decrementing the pointer.
211 */
5481ddb3 212 cmm_smp_mb();
bd252a04 213 _CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, URCU_TLS(rcu_reader)->ctr - RCU_GP_COUNT);
5481ddb3 214 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
fdee2e6d
MD
215}
216
36bc70a8
MD
217#ifdef __cplusplus
218}
219#endif
220
fdee2e6d 221#endif /* _URCU_BP_STATIC_H */
This page took 0.035879 seconds and 4 git commands to generate.