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1 | // SPDX-FileCopyrightText: 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
2 | // SPDX-FileCopyrightText: 2009 Paul E. McKenney, IBM Corporation. | |
3 | // | |
4 | // SPDX-License-Identifier: LGPL-2.1-or-later | |
5 | ||
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6 | #ifndef _URCU_MB_STATIC_H |
7 | #define _URCU_MB_STATIC_H | |
8 | ||
9 | /* | |
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10 | * Userspace RCU header. |
11 | * | |
12 | * TO BE INCLUDED ONLY IN CODE THAT IS TO BE RECOMPILED ON EACH LIBURCU | |
13 | * RELEASE. See urcu.h for linking dynamically with the userspace rcu library. | |
14 | * | |
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15 | * IBM's contributions to this file may be relicensed under LGPLv2 or later. |
16 | */ | |
17 | ||
18 | #include <stdlib.h> | |
19 | #include <pthread.h> | |
20 | #include <unistd.h> | |
21 | #include <stdint.h> | |
22 | ||
01477510 | 23 | #include <urcu/debug.h> |
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24 | #include <urcu/config.h> |
25 | #include <urcu/compiler.h> | |
26 | #include <urcu/arch.h> | |
27 | #include <urcu/system.h> | |
28 | #include <urcu/uatomic.h> | |
29 | #include <urcu/list.h> | |
30 | #include <urcu/futex.h> | |
31 | #include <urcu/tls-compat.h> | |
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32 | #include <urcu/static/urcu-common.h> |
33 | ||
34 | #ifdef __cplusplus | |
35 | extern "C" { | |
36 | #endif | |
37 | ||
38 | /* | |
39 | * This code section can only be included in LGPL 2.1 compatible source code. | |
40 | * See below for the function call wrappers which can be used in code meant to | |
41 | * be only linked with the Userspace RCU library. This comes with a small | |
42 | * performance degradation on the read-side due to the added function calls. | |
43 | * This is required to permit relinking with newer versions of the library. | |
44 | */ | |
45 | ||
46 | extern struct urcu_gp urcu_mb_gp; | |
47 | ||
48 | extern DECLARE_URCU_TLS(struct urcu_reader, urcu_mb_reader); | |
49 | ||
50 | /* | |
51 | * Helper for _urcu_mb_read_lock(). The format of urcu_mb_gp.ctr (as well as | |
be152bdb LKO |
52 | * the per-thread rcu_reader.ctr) has the lower-order bits containing a count of |
53 | * _urcu_mb_read_lock() nesting, and a single high-order URCU_BP_GP_CTR_PHASE bit | |
54 | * that contains either zero or one. The cmm_smp_mb() ensures that the accesses in | |
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55 | * _urcu_mb_read_lock() happen before the subsequent read-side critical section. |
56 | */ | |
57 | static inline void _urcu_mb_read_lock_update(unsigned long tmp) | |
58 | { | |
59 | if (caa_likely(!(tmp & URCU_GP_CTR_NEST_MASK))) { | |
60 | _CMM_STORE_SHARED(URCU_TLS(urcu_mb_reader).ctr, _CMM_LOAD_SHARED(urcu_mb_gp.ctr)); | |
61 | cmm_smp_mb(); | |
62 | } else | |
63 | _CMM_STORE_SHARED(URCU_TLS(urcu_mb_reader).ctr, tmp + URCU_GP_COUNT); | |
64 | } | |
65 | ||
66 | /* | |
67 | * Enter an RCU read-side critical section. | |
68 | * | |
69 | * The first cmm_barrier() call ensures that the compiler does not reorder | |
70 | * the body of _urcu_mb_read_lock() with a mutex. | |
71 | * | |
72 | * This function and its helper are both less than 10 lines long. The | |
73 | * intent is that this function meets the 10-line criterion in LGPL, | |
74 | * allowing this function to be invoked directly from non-LGPL code. | |
75 | */ | |
76 | static inline void _urcu_mb_read_lock(void) | |
77 | { | |
78 | unsigned long tmp; | |
79 | ||
2a27e931 | 80 | urcu_assert_debug(URCU_TLS(urcu_mb_reader).registered); |
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81 | cmm_barrier(); |
82 | tmp = URCU_TLS(urcu_mb_reader).ctr; | |
2a27e931 | 83 | urcu_assert_debug((tmp & URCU_GP_CTR_NEST_MASK) != URCU_GP_CTR_NEST_MASK); |
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84 | _urcu_mb_read_lock_update(tmp); |
85 | } | |
86 | ||
87 | /* | |
88 | * This is a helper function for _urcu_mb_read_unlock(). | |
89 | * | |
90 | * The first cmm_smp_mb() call ensures that the critical section is | |
91 | * seen to precede the store to rcu_reader.ctr. | |
92 | * The second cmm_smp_mb() call ensures that we write to rcu_reader.ctr | |
93 | * before reading the update-side futex. | |
94 | */ | |
95 | static inline void _urcu_mb_read_unlock_update_and_wakeup(unsigned long tmp) | |
96 | { | |
601922a8 OD |
97 | unsigned long *ctr = &URCU_TLS(urcu_mb_reader).ctr; |
98 | ||
4477a870 | 99 | if (caa_likely((tmp & URCU_GP_CTR_NEST_MASK) == URCU_GP_COUNT)) { |
601922a8 | 100 | uatomic_store(ctr, tmp - URCU_GP_COUNT, CMM_SEQ_CST); |
4477a870 | 101 | urcu_common_wake_up_gp(&urcu_mb_gp); |
601922a8 OD |
102 | } else { |
103 | uatomic_store(ctr, tmp - URCU_GP_COUNT, CMM_RELAXED); | |
104 | } | |
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105 | } |
106 | ||
107 | /* | |
f99c6e92 | 108 | * Exit an RCU read-side critical section. Both this function and its |
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109 | * helper are smaller than 10 lines of code, and are intended to be |
110 | * usable by non-LGPL code, as called out in LGPL. | |
111 | */ | |
112 | static inline void _urcu_mb_read_unlock(void) | |
113 | { | |
114 | unsigned long tmp; | |
115 | ||
2a27e931 | 116 | urcu_assert_debug(URCU_TLS(urcu_mb_reader).registered); |
4477a870 | 117 | tmp = URCU_TLS(urcu_mb_reader).ctr; |
2a27e931 | 118 | urcu_assert_debug(tmp & URCU_GP_CTR_NEST_MASK); |
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119 | _urcu_mb_read_unlock_update_and_wakeup(tmp); |
120 | cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */ | |
121 | } | |
122 | ||
123 | /* | |
124 | * Returns whether within a RCU read-side critical section. | |
125 | * | |
126 | * This function is less than 10 lines long. The intent is that this | |
127 | * function meets the 10-line criterion for LGPL, allowing this function | |
128 | * to be invoked directly from non-LGPL code. | |
129 | */ | |
130 | static inline int _urcu_mb_read_ongoing(void) | |
131 | { | |
132 | return URCU_TLS(urcu_mb_reader).ctr & URCU_GP_CTR_NEST_MASK; | |
133 | } | |
134 | ||
135 | #ifdef __cplusplus | |
136 | } | |
137 | #endif | |
138 | ||
139 | #endif /* _URCU_MB_STATIC_H */ |