Restrict supported arch ot P6+ on Intel x86 32.
[urcu.git] / urcu-bp-static.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 *
9 * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu.h for linking
10 * dynamically with the userspace rcu library.
11 *
12 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
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 <syscall.h>
35#include <unistd.h>
36
37#include <urcu/compiler.h>
38#include <urcu/arch.h>
39#include <urcu/system.h>
48d848c7 40#include <urcu/uatomic_arch.h>
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41#include <urcu/list.h>
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
51/*
52 * Active attempts to check for reader Q.S. before calling sleep().
53 */
54#define RCU_QS_ACTIVE_ATTEMPTS 100
55
56#ifdef DEBUG_RCU
57#define rcu_assert(args...) assert(args)
58#else
59#define rcu_assert(args...)
60#endif
61
62#ifdef DEBUG_YIELD
63#include <sched.h>
64#include <time.h>
65#include <pthread.h>
66#include <unistd.h>
67
68#define YIELD_READ (1 << 0)
69#define YIELD_WRITE (1 << 1)
70
71/*
72 * Updates without URCU_MB are much slower. Account this in
73 * the delay.
74 */
75/* maximum sleep delay, in us */
76#define MAX_SLEEP 50
77
78extern unsigned int yield_active;
79extern unsigned int __thread rand_yield;
80
81static inline void debug_yield_read(void)
82{
83 if (yield_active & YIELD_READ)
84 if (rand_r(&rand_yield) & 0x1)
85 usleep(rand_r(&rand_yield) % MAX_SLEEP);
86}
87
88static inline void debug_yield_write(void)
89{
90 if (yield_active & YIELD_WRITE)
91 if (rand_r(&rand_yield) & 0x1)
92 usleep(rand_r(&rand_yield) % MAX_SLEEP);
93}
94
95static inline void debug_yield_init(void)
96{
97 rand_yield = time(NULL) ^ pthread_self();
98}
99#else
100static inline void debug_yield_read(void)
101{
102}
103
104static inline void debug_yield_write(void)
105{
106}
107
108static inline void debug_yield_init(void)
109{
110
111}
112#endif
113
114/*
115 * The trick here is that RCU_GP_CTR_BIT must be a multiple of 8 so we can use a
116 * full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
117 */
118#define RCU_GP_COUNT (1UL << 0)
119/* Use the amount of bits equal to half of the architecture long size */
120#define RCU_GP_CTR_BIT (1UL << (sizeof(long) << 2))
121#define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_BIT - 1)
122
123/*
124 * Used internally by _rcu_read_lock.
125 */
126extern void rcu_bp_register(void);
127
128/*
129 * Global quiescent period counter with low-order bits unused.
130 * Using a int rather than a char to eliminate false register dependencies
131 * causing stalls on some architectures.
132 */
133extern long urcu_gp_ctr;
134
135struct urcu_reader {
136 /* Data used by both reader and synchronize_rcu() */
137 long ctr;
138 /* Data used for registry */
139 struct list_head head __attribute__((aligned(CACHE_LINE_SIZE)));
140 pthread_t tid;
141 int alloc; /* registry entry allocated */
142};
143
144/*
145 * Bulletproof version keeps a pointer to a registry not part of the TLS.
146 * Adds a pointer dereference on the read-side, but won't require to unregister
147 * the reader thread.
148 */
149extern struct urcu_reader __thread *urcu_reader;
150
151static inline int rcu_old_gp_ongoing(long *value)
152{
153 long v;
154
155 if (value == NULL)
156 return 0;
157 /*
158 * Make sure both tests below are done on the same version of *value
159 * to insure consistency.
160 */
161 v = LOAD_SHARED(*value);
162 return (v & RCU_GP_CTR_NEST_MASK) &&
163 ((v ^ urcu_gp_ctr) & RCU_GP_CTR_BIT);
164}
165
166static inline void _rcu_read_lock(void)
167{
168 long tmp;
169
170 /* Check if registered */
171 if (unlikely(!urcu_reader))
172 rcu_bp_register();
173
174 tmp = urcu_reader->ctr;
175 /* urcu_gp_ctr = RCU_GP_COUNT | (~RCU_GP_CTR_BIT or RCU_GP_CTR_BIT) */
176 if (likely(!(tmp & RCU_GP_CTR_NEST_MASK))) {
177 _STORE_SHARED(urcu_reader->ctr, _LOAD_SHARED(urcu_gp_ctr));
178 /*
179 * Set active readers count for outermost nesting level before
180 * accessing the pointer.
181 */
182 smp_mb();
183 } else {
184 _STORE_SHARED(urcu_reader->ctr, tmp + RCU_GP_COUNT);
185 }
186}
187
188static inline void _rcu_read_unlock(void)
189{
190 /*
191 * Finish using rcu before decrementing the pointer.
192 */
193 smp_mb();
194 _STORE_SHARED(urcu_reader->ctr, urcu_reader->ctr - RCU_GP_COUNT);
195}
196
197#endif /* _URCU_BP_STATIC_H */
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