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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> |
a77f7d82 | 42 | #include <urcu/debug.h> |
fdee2e6d MD |
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 | ||
36bc70a8 MD |
52 | #ifdef __cplusplus |
53 | extern "C" { | |
54 | #endif | |
55 | ||
52c75091 MD |
56 | enum 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 |
fdee2e6d MD |
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 */ | |
02be5561 MD |
68 | #define RCU_GP_CTR_PHASE (1UL << (sizeof(long) << 2)) |
69 | #define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_PHASE - 1) | |
fdee2e6d MD |
70 | |
71 | /* | |
72 | * Used internally by _rcu_read_lock. | |
73 | */ | |
74 | extern void rcu_bp_register(void); | |
75 | ||
c13c2e55 MD |
76 | struct 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 | ||
87 | extern struct rcu_gp rcu_gp; | |
fdee2e6d | 88 | |
02be5561 | 89 | struct 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))); |
fdee2e6d MD |
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 | 103 | extern DECLARE_URCU_TLS(struct rcu_reader *, rcu_reader); |
fdee2e6d | 104 | |
52c75091 | 105 | static inline enum rcu_state rcu_reader_state(unsigned long *ctr) |
fdee2e6d | 106 | { |
52c75091 | 107 | unsigned long v; |
fdee2e6d | 108 | |
52c75091 MD |
109 | if (ctr == NULL) |
110 | return RCU_READER_INACTIVE; | |
fdee2e6d MD |
111 | /* |
112 | * Make sure both tests below are done on the same version of *value | |
113 | * to insure consistency. | |
114 | */ | |
52c75091 MD |
115 | v = CMM_LOAD_SHARED(*ctr); |
116 | if (!(v & RCU_GP_CTR_NEST_MASK)) | |
117 | return RCU_READER_INACTIVE; | |
c13c2e55 | 118 | if (!((v ^ rcu_gp.ctr) & RCU_GP_CTR_PHASE)) |
52c75091 MD |
119 | return RCU_READER_ACTIVE_CURRENT; |
120 | return RCU_READER_ACTIVE_OLD; | |
fdee2e6d MD |
121 | } |
122 | ||
a5a9f428 | 123 | /* |
c13c2e55 | 124 | * Helper for _rcu_read_lock(). The format of rcu_gp.ctr (as well as |
a5a9f428 PM |
125 | * the per-thread rcu_reader.ctr) has the upper bits containing a count of |
126 | * _rcu_read_lock() nesting, and a lower-order bit that contains either zero | |
127 | * or RCU_GP_CTR_PHASE. The smp_mb_slave() ensures that the accesses in | |
128 | * _rcu_read_lock() happen before the subsequent read-side critical section. | |
129 | */ | |
130 | static inline void _rcu_read_lock_update(unsigned long tmp) | |
131 | { | |
132 | if (caa_likely(!(tmp & RCU_GP_CTR_NEST_MASK))) { | |
c13c2e55 | 133 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, _CMM_LOAD_SHARED(rcu_gp.ctr)); |
a5a9f428 PM |
134 | cmm_smp_mb(); |
135 | } else | |
136 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, tmp + RCU_GP_COUNT); | |
137 | } | |
138 | ||
139 | /* | |
140 | * Enter an RCU read-side critical section. | |
141 | * | |
142 | * The first cmm_barrier() call ensures that the compiler does not reorder | |
143 | * the body of _rcu_read_lock() with a mutex. | |
144 | * | |
145 | * This function and its helper are both less than 10 lines long. The | |
146 | * intent is that this function meets the 10-line criterion in LGPL, | |
147 | * allowing this function to be invoked directly from non-LGPL code. | |
148 | */ | |
fdee2e6d MD |
149 | static inline void _rcu_read_lock(void) |
150 | { | |
52c75091 | 151 | unsigned long tmp; |
fdee2e6d | 152 | |
bd252a04 | 153 | if (caa_unlikely(!URCU_TLS(rcu_reader))) |
a5a9f428 | 154 | rcu_bp_register(); /* If not yet registered. */ |
5481ddb3 | 155 | cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */ |
bd252a04 | 156 | tmp = URCU_TLS(rcu_reader)->ctr; |
a5a9f428 | 157 | _rcu_read_lock_update(tmp); |
fdee2e6d MD |
158 | } |
159 | ||
a5a9f428 PM |
160 | /* |
161 | * Exit an RCU read-side critical section. This function is less than | |
162 | * 10 lines of code, and is intended to be usable by non-LGPL code, as | |
163 | * called out in LGPL. | |
164 | */ | |
fdee2e6d MD |
165 | static inline void _rcu_read_unlock(void) |
166 | { | |
167 | /* | |
168 | * Finish using rcu before decrementing the pointer. | |
169 | */ | |
5481ddb3 | 170 | cmm_smp_mb(); |
bd252a04 | 171 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, URCU_TLS(rcu_reader)->ctr - RCU_GP_COUNT); |
5481ddb3 | 172 | cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */ |
fdee2e6d MD |
173 | } |
174 | ||
882f3357 MD |
175 | /* |
176 | * Returns whether within a RCU read-side critical section. | |
177 | * | |
178 | * This function is less than 10 lines long. The intent is that this | |
179 | * function meets the 10-line criterion for LGPL, allowing this function | |
180 | * to be invoked directly from non-LGPL code. | |
181 | */ | |
182 | static inline int _rcu_read_ongoing(void) | |
183 | { | |
184 | if (caa_unlikely(!URCU_TLS(rcu_reader))) | |
185 | rcu_bp_register(); /* If not yet registered. */ | |
186 | return URCU_TLS(rcu_reader)->ctr & RCU_GP_CTR_NEST_MASK; | |
187 | } | |
188 | ||
36bc70a8 MD |
189 | #ifdef __cplusplus |
190 | } | |
191 | #endif | |
192 | ||
fdee2e6d | 193 | #endif /* _URCU_BP_STATIC_H */ |