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5270 | serge | 1 | /* |
2 | * Read-Copy Update mechanism for mutual exclusion |
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3 | * |
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4 | * This program is free software; you can redistribute it and/or modify |
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5 | * it under the terms of the GNU General Public License as published by |
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6 | * the Free Software Foundation; either version 2 of the License, or |
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7 | * (at your option) any later version. |
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8 | * |
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9 | * This program is distributed in the hope that it will be useful, |
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10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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12 | * GNU General Public License for more details. |
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13 | * |
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14 | * You should have received a copy of the GNU General Public License |
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15 | * along with this program; if not, you can access it online at |
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16 | * http://www.gnu.org/licenses/gpl-2.0.html. |
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17 | * |
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18 | * Copyright IBM Corporation, 2001 |
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19 | * |
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20 | * Author: Dipankar Sarma |
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21 | * |
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22 | * Based on the original work by Paul McKenney |
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23 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. |
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24 | * Papers: |
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25 | * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf |
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26 | * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) |
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27 | * |
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28 | * For detailed explanation of Read-Copy Update mechanism see - |
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29 | * http://lse.sourceforge.net/locking/rcupdate.html |
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30 | * |
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31 | */ |
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32 | |||
33 | #ifndef __LINUX_RCUPDATE_H |
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34 | #define __LINUX_RCUPDATE_H |
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35 | |||
36 | #include |
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37 | #include |
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38 | #include |
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39 | #include |
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40 | //#include |
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41 | #include |
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42 | #include |
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43 | #include |
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44 | //#include |
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45 | #include |
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46 | #include |
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6082 | serge | 47 | #include |
48 | |||
5270 | serge | 49 | #include |
50 | |||
51 | extern int rcu_expedited; /* for sysctl */ |
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52 | |||
6082 | serge | 53 | #ifdef CONFIG_TINY_RCU |
54 | /* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */ |
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55 | static inline bool rcu_gp_is_expedited(void) /* Internal RCU use. */ |
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56 | { |
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57 | return false; |
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58 | } |
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59 | |||
60 | static inline void rcu_expedite_gp(void) |
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61 | { |
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62 | } |
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63 | |||
64 | static inline void rcu_unexpedite_gp(void) |
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65 | { |
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66 | } |
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67 | #else /* #ifdef CONFIG_TINY_RCU */ |
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68 | bool rcu_gp_is_expedited(void); /* Internal RCU use. */ |
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69 | void rcu_expedite_gp(void); |
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70 | void rcu_unexpedite_gp(void); |
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71 | #endif /* #else #ifdef CONFIG_TINY_RCU */ |
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72 | |||
5270 | serge | 73 | enum rcutorture_type { |
74 | RCU_FLAVOR, |
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75 | RCU_BH_FLAVOR, |
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76 | RCU_SCHED_FLAVOR, |
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77 | RCU_TASKS_FLAVOR, |
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78 | SRCU_FLAVOR, |
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79 | INVALID_RCU_FLAVOR |
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80 | }; |
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81 | |||
82 | #if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) |
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83 | void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, |
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84 | unsigned long *gpnum, unsigned long *completed); |
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85 | void rcutorture_record_test_transition(void); |
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86 | void rcutorture_record_progress(unsigned long vernum); |
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87 | void do_trace_rcu_torture_read(const char *rcutorturename, |
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88 | struct rcu_head *rhp, |
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89 | unsigned long secs, |
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90 | unsigned long c_old, |
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91 | unsigned long c); |
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92 | #else |
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93 | static inline void rcutorture_get_gp_data(enum rcutorture_type test_type, |
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94 | int *flags, |
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95 | unsigned long *gpnum, |
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96 | unsigned long *completed) |
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97 | { |
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98 | *flags = 0; |
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99 | *gpnum = 0; |
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100 | *completed = 0; |
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101 | } |
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102 | static inline void rcutorture_record_test_transition(void) |
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103 | { |
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104 | } |
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105 | static inline void rcutorture_record_progress(unsigned long vernum) |
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106 | { |
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107 | } |
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108 | #ifdef CONFIG_RCU_TRACE |
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109 | void do_trace_rcu_torture_read(const char *rcutorturename, |
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110 | struct rcu_head *rhp, |
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111 | unsigned long secs, |
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112 | unsigned long c_old, |
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113 | unsigned long c); |
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114 | #else |
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115 | #define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \ |
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116 | do { } while (0) |
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117 | #endif |
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118 | #endif |
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119 | |||
120 | #define UINT_CMP_GE(a, b) (UINT_MAX / 2 >= (a) - (b)) |
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121 | #define UINT_CMP_LT(a, b) (UINT_MAX / 2 < (a) - (b)) |
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122 | #define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b)) |
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123 | #define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b)) |
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124 | #define ulong2long(a) (*(long *)(&(a))) |
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125 | |||
126 | /* Exported common interfaces */ |
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127 | |||
128 | #ifdef CONFIG_PREEMPT_RCU |
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129 | |||
130 | /** |
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131 | * call_rcu() - Queue an RCU callback for invocation after a grace period. |
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132 | * @head: structure to be used for queueing the RCU updates. |
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133 | * @func: actual callback function to be invoked after the grace period |
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134 | * |
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135 | * The callback function will be invoked some time after a full grace |
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136 | * period elapses, in other words after all pre-existing RCU read-side |
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137 | * critical sections have completed. However, the callback function |
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138 | * might well execute concurrently with RCU read-side critical sections |
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139 | * that started after call_rcu() was invoked. RCU read-side critical |
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140 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), |
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141 | * and may be nested. |
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142 | * |
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143 | * Note that all CPUs must agree that the grace period extended beyond |
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144 | * all pre-existing RCU read-side critical section. On systems with more |
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145 | * than one CPU, this means that when "func()" is invoked, each CPU is |
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146 | * guaranteed to have executed a full memory barrier since the end of its |
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147 | * last RCU read-side critical section whose beginning preceded the call |
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148 | * to call_rcu(). It also means that each CPU executing an RCU read-side |
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149 | * critical section that continues beyond the start of "func()" must have |
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150 | * executed a memory barrier after the call_rcu() but before the beginning |
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151 | * of that RCU read-side critical section. Note that these guarantees |
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152 | * include CPUs that are offline, idle, or executing in user mode, as |
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153 | * well as CPUs that are executing in the kernel. |
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154 | * |
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155 | * Furthermore, if CPU A invoked call_rcu() and CPU B invoked the |
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156 | * resulting RCU callback function "func()", then both CPU A and CPU B are |
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157 | * guaranteed to execute a full memory barrier during the time interval |
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158 | * between the call to call_rcu() and the invocation of "func()" -- even |
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159 | * if CPU A and CPU B are the same CPU (but again only if the system has |
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160 | * more than one CPU). |
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161 | */ |
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162 | void call_rcu(struct rcu_head *head, |
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6082 | serge | 163 | rcu_callback_t func); |
5270 | serge | 164 | |
165 | #else /* #ifdef CONFIG_PREEMPT_RCU */ |
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166 | |||
167 | /* In classic RCU, call_rcu() is just call_rcu_sched(). */ |
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168 | #define call_rcu call_rcu_sched |
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169 | |||
170 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ |
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171 | |||
172 | /** |
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173 | * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period. |
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174 | * @head: structure to be used for queueing the RCU updates. |
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175 | * @func: actual callback function to be invoked after the grace period |
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176 | * |
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177 | * The callback function will be invoked some time after a full grace |
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178 | * period elapses, in other words after all currently executing RCU |
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179 | * read-side critical sections have completed. call_rcu_bh() assumes |
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180 | * that the read-side critical sections end on completion of a softirq |
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181 | * handler. This means that read-side critical sections in process |
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182 | * context must not be interrupted by softirqs. This interface is to be |
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183 | * used when most of the read-side critical sections are in softirq context. |
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184 | * RCU read-side critical sections are delimited by : |
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185 | * - rcu_read_lock() and rcu_read_unlock(), if in interrupt context. |
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186 | * OR |
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187 | * - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context. |
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188 | * These may be nested. |
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189 | * |
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190 | * See the description of call_rcu() for more detailed information on |
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191 | * memory ordering guarantees. |
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192 | */ |
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193 | void call_rcu_bh(struct rcu_head *head, |
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6082 | serge | 194 | rcu_callback_t func); |
5270 | serge | 195 | |
196 | /** |
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197 | * call_rcu_sched() - Queue an RCU for invocation after sched grace period. |
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198 | * @head: structure to be used for queueing the RCU updates. |
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199 | * @func: actual callback function to be invoked after the grace period |
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200 | * |
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201 | * The callback function will be invoked some time after a full grace |
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202 | * period elapses, in other words after all currently executing RCU |
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203 | * read-side critical sections have completed. call_rcu_sched() assumes |
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204 | * that the read-side critical sections end on enabling of preemption |
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205 | * or on voluntary preemption. |
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206 | * RCU read-side critical sections are delimited by : |
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207 | * - rcu_read_lock_sched() and rcu_read_unlock_sched(), |
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208 | * OR |
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209 | * anything that disables preemption. |
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210 | * These may be nested. |
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211 | * |
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212 | * See the description of call_rcu() for more detailed information on |
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213 | * memory ordering guarantees. |
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214 | */ |
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215 | void call_rcu_sched(struct rcu_head *head, |
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6082 | serge | 216 | rcu_callback_t func); |
5270 | serge | 217 | |
218 | void synchronize_sched(void); |
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219 | |||
6588 | serge | 220 | #define wait_rcu_gp(...) |
5270 | serge | 221 | /** |
222 | * call_rcu_tasks() - Queue an RCU for invocation task-based grace period |
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223 | * @head: structure to be used for queueing the RCU updates. |
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224 | * @func: actual callback function to be invoked after the grace period |
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225 | * |
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226 | * The callback function will be invoked some time after a full grace |
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227 | * period elapses, in other words after all currently executing RCU |
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228 | * read-side critical sections have completed. call_rcu_tasks() assumes |
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229 | * that the read-side critical sections end at a voluntary context |
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230 | * switch (not a preemption!), entry into idle, or transition to usermode |
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231 | * execution. As such, there are no read-side primitives analogous to |
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232 | * rcu_read_lock() and rcu_read_unlock() because this primitive is intended |
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233 | * to determine that all tasks have passed through a safe state, not so |
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234 | * much for data-strcuture synchronization. |
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235 | * |
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236 | * See the description of call_rcu() for more detailed information on |
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237 | * memory ordering guarantees. |
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238 | */ |
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6082 | serge | 239 | void call_rcu_tasks(struct rcu_head *head, rcu_callback_t func); |
5270 | serge | 240 | void synchronize_rcu_tasks(void); |
241 | void rcu_barrier_tasks(void); |
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242 | |||
243 | #ifdef CONFIG_PREEMPT_RCU |
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244 | |||
245 | void __rcu_read_lock(void); |
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246 | void __rcu_read_unlock(void); |
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247 | void rcu_read_unlock_special(struct task_struct *t); |
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248 | void synchronize_rcu(void); |
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249 | |||
250 | /* |
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251 | * Defined as a macro as it is a very low level header included from |
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252 | * areas that don't even know about current. This gives the rcu_read_lock() |
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253 | * nesting depth, but makes sense only if CONFIG_PREEMPT_RCU -- in other |
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254 | * types of kernel builds, the rcu_read_lock() nesting depth is unknowable. |
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255 | */ |
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256 | #define rcu_preempt_depth() (current->rcu_read_lock_nesting) |
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257 | |||
258 | #else /* #ifdef CONFIG_PREEMPT_RCU */ |
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259 | |||
260 | static inline void __rcu_read_lock(void) |
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261 | { |
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6082 | serge | 262 | if (IS_ENABLED(CONFIG_PREEMPT_COUNT)) |
263 | preempt_disable(); |
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5270 | serge | 264 | } |
265 | |||
266 | static inline void __rcu_read_unlock(void) |
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267 | { |
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6082 | serge | 268 | if (IS_ENABLED(CONFIG_PREEMPT_COUNT)) |
269 | preempt_enable(); |
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5270 | serge | 270 | } |
271 | |||
272 | static inline void synchronize_rcu(void) |
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273 | { |
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274 | synchronize_sched(); |
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275 | } |
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276 | |||
277 | static inline int rcu_preempt_depth(void) |
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278 | { |
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279 | return 0; |
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280 | } |
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281 | |||
282 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ |
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283 | |||
284 | /* Internal to kernel */ |
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285 | void rcu_init(void); |
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6082 | serge | 286 | void rcu_end_inkernel_boot(void); |
5270 | serge | 287 | void rcu_sched_qs(void); |
288 | void rcu_bh_qs(void); |
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289 | void rcu_check_callbacks(int user); |
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290 | struct notifier_block; |
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6082 | serge | 291 | int rcu_cpu_notify(struct notifier_block *self, |
292 | unsigned long action, void *hcpu); |
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5270 | serge | 293 | |
294 | #ifdef CONFIG_RCU_STALL_COMMON |
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295 | void rcu_sysrq_start(void); |
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296 | void rcu_sysrq_end(void); |
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297 | #else /* #ifdef CONFIG_RCU_STALL_COMMON */ |
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298 | static inline void rcu_sysrq_start(void) |
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299 | { |
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300 | } |
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301 | static inline void rcu_sysrq_end(void) |
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302 | { |
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303 | } |
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304 | #endif /* #else #ifdef CONFIG_RCU_STALL_COMMON */ |
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305 | |||
6082 | serge | 306 | #ifdef CONFIG_NO_HZ_FULL |
5270 | serge | 307 | void rcu_user_enter(void); |
308 | void rcu_user_exit(void); |
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309 | #else |
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310 | static inline void rcu_user_enter(void) { } |
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311 | static inline void rcu_user_exit(void) { } |
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312 | static inline void rcu_user_hooks_switch(struct task_struct *prev, |
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313 | struct task_struct *next) { } |
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6082 | serge | 314 | #endif /* CONFIG_NO_HZ_FULL */ |
5270 | serge | 315 | |
316 | #ifdef CONFIG_RCU_NOCB_CPU |
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317 | void rcu_init_nohz(void); |
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318 | #else /* #ifdef CONFIG_RCU_NOCB_CPU */ |
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319 | static inline void rcu_init_nohz(void) |
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320 | { |
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321 | } |
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322 | #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ |
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323 | |||
324 | /** |
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325 | * RCU_NONIDLE - Indicate idle-loop code that needs RCU readers |
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326 | * @a: Code that RCU needs to pay attention to. |
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327 | * |
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328 | * RCU, RCU-bh, and RCU-sched read-side critical sections are forbidden |
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329 | * in the inner idle loop, that is, between the rcu_idle_enter() and |
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330 | * the rcu_idle_exit() -- RCU will happily ignore any such read-side |
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331 | * critical sections. However, things like powertop need tracepoints |
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332 | * in the inner idle loop. |
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333 | * |
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334 | * This macro provides the way out: RCU_NONIDLE(do_something_with_RCU()) |
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335 | * will tell RCU that it needs to pay attending, invoke its argument |
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336 | * (in this example, a call to the do_something_with_RCU() function), |
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337 | * and then tell RCU to go back to ignoring this CPU. It is permissible |
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338 | * to nest RCU_NONIDLE() wrappers, but the nesting level is currently |
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339 | * quite limited. If deeper nesting is required, it will be necessary |
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340 | * to adjust DYNTICK_TASK_NESTING_VALUE accordingly. |
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341 | */ |
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342 | #define RCU_NONIDLE(a) \ |
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343 | do { \ |
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344 | rcu_irq_enter(); \ |
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345 | do { a; } while (0); \ |
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346 | rcu_irq_exit(); \ |
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347 | } while (0) |
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348 | |||
349 | /* |
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350 | * Note a voluntary context switch for RCU-tasks benefit. This is a |
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351 | * macro rather than an inline function to avoid #include hell. |
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352 | */ |
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353 | #ifdef CONFIG_TASKS_RCU |
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354 | #define TASKS_RCU(x) x |
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355 | extern struct srcu_struct tasks_rcu_exit_srcu; |
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356 | #define rcu_note_voluntary_context_switch(t) \ |
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357 | do { \ |
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6082 | serge | 358 | rcu_all_qs(); \ |
359 | if (READ_ONCE((t)->rcu_tasks_holdout)) \ |
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360 | WRITE_ONCE((t)->rcu_tasks_holdout, false); \ |
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5270 | serge | 361 | } while (0) |
362 | #else /* #ifdef CONFIG_TASKS_RCU */ |
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363 | #define TASKS_RCU(x) do { } while (0) |
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6082 | serge | 364 | #define rcu_note_voluntary_context_switch(t) rcu_all_qs() |
5270 | serge | 365 | #endif /* #else #ifdef CONFIG_TASKS_RCU */ |
366 | |||
367 | /** |
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368 | * cond_resched_rcu_qs - Report potential quiescent states to RCU |
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369 | * |
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370 | * This macro resembles cond_resched(), except that it is defined to |
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371 | * report potential quiescent states to RCU-tasks even if the cond_resched() |
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372 | * machinery were to be shut off, as some advocate for PREEMPT kernels. |
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373 | */ |
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374 | #define cond_resched_rcu_qs() \ |
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375 | do { \ |
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376 | if (!cond_resched()) \ |
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377 | rcu_note_voluntary_context_switch(current); \ |
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378 | } while (0) |
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379 | |||
380 | #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP) |
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381 | bool __rcu_is_watching(void); |
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382 | #endif /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP) */ |
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383 | |||
384 | /* |
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385 | * Infrastructure to implement the synchronize_() primitives in |
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386 | * TREE_RCU and rcu_barrier_() primitives in TINY_RCU. |
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387 | */ |
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388 | |||
389 | #if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) |
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390 | #include |
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391 | #elif defined(CONFIG_TINY_RCU) |
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392 | #include |
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393 | #else |
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394 | #error "Unknown RCU implementation specified to kernel configuration" |
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395 | #endif |
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396 | |||
397 | /* |
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398 | * init_rcu_head_on_stack()/destroy_rcu_head_on_stack() are needed for dynamic |
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399 | * initialization and destruction of rcu_head on the stack. rcu_head structures |
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400 | * allocated dynamically in the heap or defined statically don't need any |
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401 | * initialization. |
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402 | */ |
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403 | #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD |
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404 | void init_rcu_head(struct rcu_head *head); |
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405 | void destroy_rcu_head(struct rcu_head *head); |
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406 | void init_rcu_head_on_stack(struct rcu_head *head); |
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407 | void destroy_rcu_head_on_stack(struct rcu_head *head); |
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408 | #else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
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409 | static inline void init_rcu_head(struct rcu_head *head) |
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410 | { |
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411 | } |
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412 | |||
413 | static inline void destroy_rcu_head(struct rcu_head *head) |
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414 | { |
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415 | } |
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416 | |||
417 | static inline void init_rcu_head_on_stack(struct rcu_head *head) |
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418 | { |
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419 | } |
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420 | |||
421 | static inline void destroy_rcu_head_on_stack(struct rcu_head *head) |
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422 | { |
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423 | } |
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424 | #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
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425 | |||
426 | #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) |
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427 | bool rcu_lockdep_current_cpu_online(void); |
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428 | #else /* #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ |
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429 | static inline bool rcu_lockdep_current_cpu_online(void) |
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430 | { |
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431 | return true; |
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432 | } |
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433 | #endif /* #else #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ |
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434 | |||
435 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
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436 | |||
437 | static inline void rcu_lock_acquire(struct lockdep_map *map) |
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438 | { |
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439 | lock_acquire(map, 0, 0, 2, 0, NULL, _THIS_IP_); |
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440 | } |
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441 | |||
442 | static inline void rcu_lock_release(struct lockdep_map *map) |
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443 | { |
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444 | lock_release(map, 1, _THIS_IP_); |
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445 | } |
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446 | |||
447 | extern struct lockdep_map rcu_lock_map; |
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448 | extern struct lockdep_map rcu_bh_lock_map; |
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449 | extern struct lockdep_map rcu_sched_lock_map; |
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450 | extern struct lockdep_map rcu_callback_map; |
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451 | int debug_lockdep_rcu_enabled(void); |
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452 | |||
453 | int rcu_read_lock_held(void); |
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454 | int rcu_read_lock_bh_held(void); |
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455 | |||
456 | /** |
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457 | * rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section? |
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458 | * |
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459 | * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an |
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460 | * RCU-sched read-side critical section. In absence of |
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461 | * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side |
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6295 | serge | 462 | * critical section unless it can prove otherwise. |
5270 | serge | 463 | */ |
464 | #ifdef CONFIG_PREEMPT_COUNT |
||
6295 | serge | 465 | int rcu_read_lock_sched_held(void); |
5270 | serge | 466 | #else /* #ifdef CONFIG_PREEMPT_COUNT */ |
467 | static inline int rcu_read_lock_sched_held(void) |
||
468 | { |
||
469 | return 1; |
||
470 | } |
||
471 | #endif /* #else #ifdef CONFIG_PREEMPT_COUNT */ |
||
472 | |||
473 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
||
474 | |||
475 | # define rcu_lock_acquire(a) do { } while (0) |
||
476 | # define rcu_lock_release(a) do { } while (0) |
||
477 | |||
478 | static inline int rcu_read_lock_held(void) |
||
479 | { |
||
480 | return 1; |
||
481 | } |
||
482 | |||
483 | static inline int rcu_read_lock_bh_held(void) |
||
484 | { |
||
485 | return 1; |
||
486 | } |
||
487 | |||
488 | #ifdef CONFIG_PREEMPT_COUNT |
||
489 | static inline int rcu_read_lock_sched_held(void) |
||
490 | { |
||
491 | return preempt_count() != 0 || irqs_disabled(); |
||
492 | } |
||
493 | #else /* #ifdef CONFIG_PREEMPT_COUNT */ |
||
494 | static inline int rcu_read_lock_sched_held(void) |
||
495 | { |
||
496 | return 1; |
||
497 | } |
||
498 | #endif /* #else #ifdef CONFIG_PREEMPT_COUNT */ |
||
499 | |||
500 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
||
501 | |||
502 | #ifdef CONFIG_PROVE_RCU |
||
503 | |||
504 | /** |
||
6295 | serge | 505 | * RCU_LOCKDEP_WARN - emit lockdep splat if specified condition is met |
5270 | serge | 506 | * @c: condition to check |
507 | * @s: informative message |
||
508 | */ |
||
6295 | serge | 509 | #define RCU_LOCKDEP_WARN(c, s) \ |
5270 | serge | 510 | do { \ |
511 | static bool __section(.data.unlikely) __warned; \ |
||
6295 | serge | 512 | if (debug_lockdep_rcu_enabled() && !__warned && (c)) { \ |
5270 | serge | 513 | __warned = true; \ |
514 | lockdep_rcu_suspicious(__FILE__, __LINE__, s); \ |
||
515 | } \ |
||
516 | } while (0) |
||
517 | |||
518 | #if defined(CONFIG_PROVE_RCU) && !defined(CONFIG_PREEMPT_RCU) |
||
519 | static inline void rcu_preempt_sleep_check(void) |
||
520 | { |
||
6295 | serge | 521 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_lock_map), |
5270 | serge | 522 | "Illegal context switch in RCU read-side critical section"); |
523 | } |
||
524 | #else /* #ifdef CONFIG_PROVE_RCU */ |
||
525 | static inline void rcu_preempt_sleep_check(void) |
||
526 | { |
||
527 | } |
||
528 | #endif /* #else #ifdef CONFIG_PROVE_RCU */ |
||
529 | |||
530 | #define rcu_sleep_check() \ |
||
531 | do { \ |
||
532 | rcu_preempt_sleep_check(); \ |
||
6295 | serge | 533 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map), \ |
5270 | serge | 534 | "Illegal context switch in RCU-bh read-side critical section"); \ |
6295 | serge | 535 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_sched_lock_map), \ |
5270 | serge | 536 | "Illegal context switch in RCU-sched read-side critical section"); \ |
537 | } while (0) |
||
538 | |||
539 | #else /* #ifdef CONFIG_PROVE_RCU */ |
||
540 | |||
6295 | serge | 541 | #define RCU_LOCKDEP_WARN(c, s) do { } while (0) |
5270 | serge | 542 | #define rcu_sleep_check() do { } while (0) |
543 | |||
544 | #endif /* #else #ifdef CONFIG_PROVE_RCU */ |
||
545 | |||
546 | /* |
||
547 | * Helper functions for rcu_dereference_check(), rcu_dereference_protected() |
||
548 | * and rcu_assign_pointer(). Some of these could be folded into their |
||
549 | * callers, but they are left separate in order to ease introduction of |
||
550 | * multiple flavors of pointers to match the multiple flavors of RCU |
||
551 | * (e.g., __rcu_bh, * __rcu_sched, and __srcu), should this make sense in |
||
552 | * the future. |
||
553 | */ |
||
554 | |||
555 | #ifdef __CHECKER__ |
||
556 | #define rcu_dereference_sparse(p, space) \ |
||
557 | ((void)(((typeof(*p) space *)p) == p)) |
||
558 | #else /* #ifdef __CHECKER__ */ |
||
559 | #define rcu_dereference_sparse(p, space) |
||
560 | #endif /* #else #ifdef __CHECKER__ */ |
||
561 | |||
562 | #define __rcu_access_pointer(p, space) \ |
||
563 | ({ \ |
||
6082 | serge | 564 | typeof(*p) *_________p1 = (typeof(*p) *__force)READ_ONCE(p); \ |
5270 | serge | 565 | rcu_dereference_sparse(p, space); \ |
566 | ((typeof(*p) __force __kernel *)(_________p1)); \ |
||
567 | }) |
||
568 | #define __rcu_dereference_check(p, c, space) \ |
||
569 | ({ \ |
||
6082 | serge | 570 | /* Dependency order vs. p above. */ \ |
571 | typeof(*p) *________p1 = (typeof(*p) *__force)lockless_dereference(p); \ |
||
6295 | serge | 572 | RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_check() usage"); \ |
5270 | serge | 573 | rcu_dereference_sparse(p, space); \ |
6082 | serge | 574 | ((typeof(*p) __force __kernel *)(________p1)); \ |
5270 | serge | 575 | }) |
576 | #define __rcu_dereference_protected(p, c, space) \ |
||
577 | ({ \ |
||
6295 | serge | 578 | RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_protected() usage"); \ |
5270 | serge | 579 | rcu_dereference_sparse(p, space); \ |
580 | ((typeof(*p) __force __kernel *)(p)); \ |
||
581 | }) |
||
582 | |||
583 | /** |
||
584 | * RCU_INITIALIZER() - statically initialize an RCU-protected global variable |
||
585 | * @v: The value to statically initialize with. |
||
586 | */ |
||
587 | #define RCU_INITIALIZER(v) (typeof(*(v)) __force __rcu *)(v) |
||
588 | |||
589 | /** |
||
590 | * rcu_assign_pointer() - assign to RCU-protected pointer |
||
591 | * @p: pointer to assign to |
||
592 | * @v: value to assign (publish) |
||
593 | * |
||
594 | * Assigns the specified value to the specified RCU-protected |
||
595 | * pointer, ensuring that any concurrent RCU readers will see |
||
596 | * any prior initialization. |
||
597 | * |
||
598 | * Inserts memory barriers on architectures that require them |
||
599 | * (which is most of them), and also prevents the compiler from |
||
600 | * reordering the code that initializes the structure after the pointer |
||
601 | * assignment. More importantly, this call documents which pointers |
||
602 | * will be dereferenced by RCU read-side code. |
||
603 | * |
||
604 | * In some special cases, you may use RCU_INIT_POINTER() instead |
||
605 | * of rcu_assign_pointer(). RCU_INIT_POINTER() is a bit faster due |
||
606 | * to the fact that it does not constrain either the CPU or the compiler. |
||
607 | * That said, using RCU_INIT_POINTER() when you should have used |
||
608 | * rcu_assign_pointer() is a very bad thing that results in |
||
609 | * impossible-to-diagnose memory corruption. So please be careful. |
||
610 | * See the RCU_INIT_POINTER() comment header for details. |
||
611 | * |
||
612 | * Note that rcu_assign_pointer() evaluates each of its arguments only |
||
613 | * once, appearances notwithstanding. One of the "extra" evaluations |
||
614 | * is in typeof() and the other visible only to sparse (__CHECKER__), |
||
615 | * neither of which actually execute the argument. As with most cpp |
||
616 | * macros, this execute-arguments-only-once property is important, so |
||
617 | * please be careful when making changes to rcu_assign_pointer() and the |
||
618 | * other macros that it invokes. |
||
619 | */ |
||
620 | #define rcu_assign_pointer(p, v) smp_store_release(&p, RCU_INITIALIZER(v)) |
||
621 | |||
622 | /** |
||
623 | * rcu_access_pointer() - fetch RCU pointer with no dereferencing |
||
624 | * @p: The pointer to read |
||
625 | * |
||
626 | * Return the value of the specified RCU-protected pointer, but omit the |
||
6082 | serge | 627 | * smp_read_barrier_depends() and keep the READ_ONCE(). This is useful |
5270 | serge | 628 | * when the value of this pointer is accessed, but the pointer is not |
629 | * dereferenced, for example, when testing an RCU-protected pointer against |
||
630 | * NULL. Although rcu_access_pointer() may also be used in cases where |
||
631 | * update-side locks prevent the value of the pointer from changing, you |
||
632 | * should instead use rcu_dereference_protected() for this use case. |
||
633 | * |
||
634 | * It is also permissible to use rcu_access_pointer() when read-side |
||
635 | * access to the pointer was removed at least one grace period ago, as |
||
636 | * is the case in the context of the RCU callback that is freeing up |
||
637 | * the data, or after a synchronize_rcu() returns. This can be useful |
||
638 | * when tearing down multi-linked structures after a grace period |
||
639 | * has elapsed. |
||
640 | */ |
||
641 | #define rcu_access_pointer(p) __rcu_access_pointer((p), __rcu) |
||
642 | |||
643 | /** |
||
644 | * rcu_dereference_check() - rcu_dereference with debug checking |
||
645 | * @p: The pointer to read, prior to dereferencing |
||
646 | * @c: The conditions under which the dereference will take place |
||
647 | * |
||
648 | * Do an rcu_dereference(), but check that the conditions under which the |
||
649 | * dereference will take place are correct. Typically the conditions |
||
650 | * indicate the various locking conditions that should be held at that |
||
651 | * point. The check should return true if the conditions are satisfied. |
||
652 | * An implicit check for being in an RCU read-side critical section |
||
653 | * (rcu_read_lock()) is included. |
||
654 | * |
||
655 | * For example: |
||
656 | * |
||
657 | * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock)); |
||
658 | * |
||
659 | * could be used to indicate to lockdep that foo->bar may only be dereferenced |
||
660 | * if either rcu_read_lock() is held, or that the lock required to replace |
||
661 | * the bar struct at foo->bar is held. |
||
662 | * |
||
663 | * Note that the list of conditions may also include indications of when a lock |
||
664 | * need not be held, for example during initialisation or destruction of the |
||
665 | * target struct: |
||
666 | * |
||
667 | * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock) || |
||
668 | * atomic_read(&foo->usage) == 0); |
||
669 | * |
||
670 | * Inserts memory barriers on architectures that require them |
||
671 | * (currently only the Alpha), prevents the compiler from refetching |
||
672 | * (and from merging fetches), and, more importantly, documents exactly |
||
673 | * which pointers are protected by RCU and checks that the pointer is |
||
674 | * annotated as __rcu. |
||
675 | */ |
||
676 | #define rcu_dereference_check(p, c) \ |
||
6082 | serge | 677 | __rcu_dereference_check((p), (c) || rcu_read_lock_held(), __rcu) |
5270 | serge | 678 | |
679 | /** |
||
680 | * rcu_dereference_bh_check() - rcu_dereference_bh with debug checking |
||
681 | * @p: The pointer to read, prior to dereferencing |
||
682 | * @c: The conditions under which the dereference will take place |
||
683 | * |
||
684 | * This is the RCU-bh counterpart to rcu_dereference_check(). |
||
685 | */ |
||
686 | #define rcu_dereference_bh_check(p, c) \ |
||
6082 | serge | 687 | __rcu_dereference_check((p), (c) || rcu_read_lock_bh_held(), __rcu) |
5270 | serge | 688 | |
689 | /** |
||
690 | * rcu_dereference_sched_check() - rcu_dereference_sched with debug checking |
||
691 | * @p: The pointer to read, prior to dereferencing |
||
692 | * @c: The conditions under which the dereference will take place |
||
693 | * |
||
694 | * This is the RCU-sched counterpart to rcu_dereference_check(). |
||
695 | */ |
||
696 | #define rcu_dereference_sched_check(p, c) \ |
||
6082 | serge | 697 | __rcu_dereference_check((p), (c) || rcu_read_lock_sched_held(), \ |
5270 | serge | 698 | __rcu) |
699 | |||
700 | #define rcu_dereference_raw(p) rcu_dereference_check(p, 1) /*@@@ needed? @@@*/ |
||
701 | |||
702 | /* |
||
703 | * The tracing infrastructure traces RCU (we want that), but unfortunately |
||
704 | * some of the RCU checks causes tracing to lock up the system. |
||
705 | * |
||
706 | * The tracing version of rcu_dereference_raw() must not call |
||
707 | * rcu_read_lock_held(). |
||
708 | */ |
||
709 | #define rcu_dereference_raw_notrace(p) __rcu_dereference_check((p), 1, __rcu) |
||
710 | |||
711 | /** |
||
712 | * rcu_dereference_protected() - fetch RCU pointer when updates prevented |
||
713 | * @p: The pointer to read, prior to dereferencing |
||
714 | * @c: The conditions under which the dereference will take place |
||
715 | * |
||
716 | * Return the value of the specified RCU-protected pointer, but omit |
||
6082 | serge | 717 | * both the smp_read_barrier_depends() and the READ_ONCE(). This |
5270 | serge | 718 | * is useful in cases where update-side locks prevent the value of the |
719 | * pointer from changing. Please note that this primitive does -not- |
||
720 | * prevent the compiler from repeating this reference or combining it |
||
721 | * with other references, so it should not be used without protection |
||
722 | * of appropriate locks. |
||
723 | * |
||
724 | * This function is only for update-side use. Using this function |
||
725 | * when protected only by rcu_read_lock() will result in infrequent |
||
726 | * but very ugly failures. |
||
727 | */ |
||
728 | #define rcu_dereference_protected(p, c) \ |
||
729 | __rcu_dereference_protected((p), (c), __rcu) |
||
730 | |||
731 | |||
732 | /** |
||
733 | * rcu_dereference() - fetch RCU-protected pointer for dereferencing |
||
734 | * @p: The pointer to read, prior to dereferencing |
||
735 | * |
||
736 | * This is a simple wrapper around rcu_dereference_check(). |
||
737 | */ |
||
738 | #define rcu_dereference(p) rcu_dereference_check(p, 0) |
||
739 | |||
740 | /** |
||
741 | * rcu_dereference_bh() - fetch an RCU-bh-protected pointer for dereferencing |
||
742 | * @p: The pointer to read, prior to dereferencing |
||
743 | * |
||
744 | * Makes rcu_dereference_check() do the dirty work. |
||
745 | */ |
||
746 | #define rcu_dereference_bh(p) rcu_dereference_bh_check(p, 0) |
||
747 | |||
748 | /** |
||
749 | * rcu_dereference_sched() - fetch RCU-sched-protected pointer for dereferencing |
||
750 | * @p: The pointer to read, prior to dereferencing |
||
751 | * |
||
752 | * Makes rcu_dereference_check() do the dirty work. |
||
753 | */ |
||
754 | #define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0) |
||
755 | |||
756 | /** |
||
757 | * rcu_read_lock() - mark the beginning of an RCU read-side critical section |
||
758 | * |
||
759 | * When synchronize_rcu() is invoked on one CPU while other CPUs |
||
760 | * are within RCU read-side critical sections, then the |
||
761 | * synchronize_rcu() is guaranteed to block until after all the other |
||
762 | * CPUs exit their critical sections. Similarly, if call_rcu() is invoked |
||
763 | * on one CPU while other CPUs are within RCU read-side critical |
||
764 | * sections, invocation of the corresponding RCU callback is deferred |
||
765 | * until after the all the other CPUs exit their critical sections. |
||
766 | * |
||
767 | * Note, however, that RCU callbacks are permitted to run concurrently |
||
768 | * with new RCU read-side critical sections. One way that this can happen |
||
769 | * is via the following sequence of events: (1) CPU 0 enters an RCU |
||
770 | * read-side critical section, (2) CPU 1 invokes call_rcu() to register |
||
771 | * an RCU callback, (3) CPU 0 exits the RCU read-side critical section, |
||
772 | * (4) CPU 2 enters a RCU read-side critical section, (5) the RCU |
||
773 | * callback is invoked. This is legal, because the RCU read-side critical |
||
774 | * section that was running concurrently with the call_rcu() (and which |
||
775 | * therefore might be referencing something that the corresponding RCU |
||
776 | * callback would free up) has completed before the corresponding |
||
777 | * RCU callback is invoked. |
||
778 | * |
||
779 | * RCU read-side critical sections may be nested. Any deferred actions |
||
780 | * will be deferred until the outermost RCU read-side critical section |
||
781 | * completes. |
||
782 | * |
||
783 | * You can avoid reading and understanding the next paragraph by |
||
784 | * following this rule: don't put anything in an rcu_read_lock() RCU |
||
785 | * read-side critical section that would block in a !PREEMPT kernel. |
||
786 | * But if you want the full story, read on! |
||
787 | * |
||
788 | * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU), |
||
789 | * it is illegal to block while in an RCU read-side critical section. |
||
790 | * In preemptible RCU implementations (PREEMPT_RCU) in CONFIG_PREEMPT |
||
791 | * kernel builds, RCU read-side critical sections may be preempted, |
||
792 | * but explicit blocking is illegal. Finally, in preemptible RCU |
||
793 | * implementations in real-time (with -rt patchset) kernel builds, RCU |
||
794 | * read-side critical sections may be preempted and they may also block, but |
||
795 | * only when acquiring spinlocks that are subject to priority inheritance. |
||
796 | */ |
||
797 | static inline void rcu_read_lock(void) |
||
798 | { |
||
799 | __rcu_read_lock(); |
||
800 | __acquire(RCU); |
||
801 | rcu_lock_acquire(&rcu_lock_map); |
||
6295 | serge | 802 | RCU_LOCKDEP_WARN(!rcu_is_watching(), |
5270 | serge | 803 | "rcu_read_lock() used illegally while idle"); |
804 | } |
||
805 | |||
806 | /* |
||
807 | * So where is rcu_write_lock()? It does not exist, as there is no |
||
808 | * way for writers to lock out RCU readers. This is a feature, not |
||
809 | * a bug -- this property is what provides RCU's performance benefits. |
||
810 | * Of course, writers must coordinate with each other. The normal |
||
811 | * spinlock primitives work well for this, but any other technique may be |
||
812 | * used as well. RCU does not care how the writers keep out of each |
||
813 | * others' way, as long as they do so. |
||
814 | */ |
||
815 | |||
816 | /** |
||
817 | * rcu_read_unlock() - marks the end of an RCU read-side critical section. |
||
818 | * |
||
819 | * In most situations, rcu_read_unlock() is immune from deadlock. |
||
820 | * However, in kernels built with CONFIG_RCU_BOOST, rcu_read_unlock() |
||
821 | * is responsible for deboosting, which it does via rt_mutex_unlock(). |
||
822 | * Unfortunately, this function acquires the scheduler's runqueue and |
||
823 | * priority-inheritance spinlocks. This means that deadlock could result |
||
824 | * if the caller of rcu_read_unlock() already holds one of these locks or |
||
825 | * any lock that is ever acquired while holding them; or any lock which |
||
826 | * can be taken from interrupt context because rcu_boost()->rt_mutex_lock() |
||
827 | * does not disable irqs while taking ->wait_lock. |
||
828 | * |
||
829 | * That said, RCU readers are never priority boosted unless they were |
||
830 | * preempted. Therefore, one way to avoid deadlock is to make sure |
||
831 | * that preemption never happens within any RCU read-side critical |
||
832 | * section whose outermost rcu_read_unlock() is called with one of |
||
833 | * rt_mutex_unlock()'s locks held. Such preemption can be avoided in |
||
834 | * a number of ways, for example, by invoking preempt_disable() before |
||
835 | * critical section's outermost rcu_read_lock(). |
||
836 | * |
||
837 | * Given that the set of locks acquired by rt_mutex_unlock() might change |
||
838 | * at any time, a somewhat more future-proofed approach is to make sure |
||
839 | * that that preemption never happens within any RCU read-side critical |
||
840 | * section whose outermost rcu_read_unlock() is called with irqs disabled. |
||
841 | * This approach relies on the fact that rt_mutex_unlock() currently only |
||
842 | * acquires irq-disabled locks. |
||
843 | * |
||
844 | * The second of these two approaches is best in most situations, |
||
845 | * however, the first approach can also be useful, at least to those |
||
846 | * developers willing to keep abreast of the set of locks acquired by |
||
847 | * rt_mutex_unlock(). |
||
848 | * |
||
849 | * See rcu_read_lock() for more information. |
||
850 | */ |
||
851 | static inline void rcu_read_unlock(void) |
||
852 | { |
||
6295 | serge | 853 | RCU_LOCKDEP_WARN(!rcu_is_watching(), |
5270 | serge | 854 | "rcu_read_unlock() used illegally while idle"); |
855 | __release(RCU); |
||
856 | __rcu_read_unlock(); |
||
6082 | serge | 857 | rcu_lock_release(&rcu_lock_map); /* Keep acq info for rls diags. */ |
5270 | serge | 858 | } |
859 | |||
860 | /** |
||
861 | * rcu_read_lock_bh() - mark the beginning of an RCU-bh critical section |
||
862 | * |
||
863 | * This is equivalent of rcu_read_lock(), but to be used when updates |
||
864 | * are being done using call_rcu_bh() or synchronize_rcu_bh(). Since |
||
865 | * both call_rcu_bh() and synchronize_rcu_bh() consider completion of a |
||
866 | * softirq handler to be a quiescent state, a process in RCU read-side |
||
867 | * critical section must be protected by disabling softirqs. Read-side |
||
868 | * critical sections in interrupt context can use just rcu_read_lock(), |
||
869 | * though this should at least be commented to avoid confusing people |
||
870 | * reading the code. |
||
871 | * |
||
872 | * Note that rcu_read_lock_bh() and the matching rcu_read_unlock_bh() |
||
873 | * must occur in the same context, for example, it is illegal to invoke |
||
874 | * rcu_read_unlock_bh() from one task if the matching rcu_read_lock_bh() |
||
875 | * was invoked from some other task. |
||
876 | */ |
||
877 | static inline void rcu_read_lock_bh(void) |
||
878 | { |
||
879 | local_bh_disable(); |
||
880 | __acquire(RCU_BH); |
||
881 | rcu_lock_acquire(&rcu_bh_lock_map); |
||
6295 | serge | 882 | RCU_LOCKDEP_WARN(!rcu_is_watching(), |
5270 | serge | 883 | "rcu_read_lock_bh() used illegally while idle"); |
884 | } |
||
885 | |||
886 | /* |
||
887 | * rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section |
||
888 | * |
||
889 | * See rcu_read_lock_bh() for more information. |
||
890 | */ |
||
891 | static inline void rcu_read_unlock_bh(void) |
||
892 | { |
||
6295 | serge | 893 | RCU_LOCKDEP_WARN(!rcu_is_watching(), |
5270 | serge | 894 | "rcu_read_unlock_bh() used illegally while idle"); |
895 | rcu_lock_release(&rcu_bh_lock_map); |
||
896 | __release(RCU_BH); |
||
897 | local_bh_enable(); |
||
898 | } |
||
899 | |||
900 | /** |
||
901 | * rcu_read_lock_sched() - mark the beginning of a RCU-sched critical section |
||
902 | * |
||
903 | * This is equivalent of rcu_read_lock(), but to be used when updates |
||
904 | * are being done using call_rcu_sched() or synchronize_rcu_sched(). |
||
905 | * Read-side critical sections can also be introduced by anything that |
||
906 | * disables preemption, including local_irq_disable() and friends. |
||
907 | * |
||
908 | * Note that rcu_read_lock_sched() and the matching rcu_read_unlock_sched() |
||
909 | * must occur in the same context, for example, it is illegal to invoke |
||
910 | * rcu_read_unlock_sched() from process context if the matching |
||
911 | * rcu_read_lock_sched() was invoked from an NMI handler. |
||
912 | */ |
||
913 | static inline void rcu_read_lock_sched(void) |
||
914 | { |
||
915 | preempt_disable(); |
||
916 | __acquire(RCU_SCHED); |
||
917 | rcu_lock_acquire(&rcu_sched_lock_map); |
||
6295 | serge | 918 | RCU_LOCKDEP_WARN(!rcu_is_watching(), |
5270 | serge | 919 | "rcu_read_lock_sched() used illegally while idle"); |
920 | } |
||
921 | |||
922 | /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ |
||
923 | static inline notrace void rcu_read_lock_sched_notrace(void) |
||
924 | { |
||
925 | preempt_disable_notrace(); |
||
926 | __acquire(RCU_SCHED); |
||
927 | } |
||
928 | |||
929 | /* |
||
930 | * rcu_read_unlock_sched - marks the end of a RCU-classic critical section |
||
931 | * |
||
932 | * See rcu_read_lock_sched for more information. |
||
933 | */ |
||
934 | static inline void rcu_read_unlock_sched(void) |
||
935 | { |
||
6295 | serge | 936 | RCU_LOCKDEP_WARN(!rcu_is_watching(), |
5270 | serge | 937 | "rcu_read_unlock_sched() used illegally while idle"); |
938 | rcu_lock_release(&rcu_sched_lock_map); |
||
939 | __release(RCU_SCHED); |
||
940 | preempt_enable(); |
||
941 | } |
||
942 | |||
943 | /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ |
||
944 | static inline notrace void rcu_read_unlock_sched_notrace(void) |
||
945 | { |
||
946 | __release(RCU_SCHED); |
||
947 | preempt_enable_notrace(); |
||
948 | } |
||
949 | |||
950 | /** |
||
951 | * RCU_INIT_POINTER() - initialize an RCU protected pointer |
||
952 | * |
||
953 | * Initialize an RCU-protected pointer in special cases where readers |
||
954 | * do not need ordering constraints on the CPU or the compiler. These |
||
955 | * special cases are: |
||
956 | * |
||
957 | * 1. This use of RCU_INIT_POINTER() is NULLing out the pointer -or- |
||
958 | * 2. The caller has taken whatever steps are required to prevent |
||
959 | * RCU readers from concurrently accessing this pointer -or- |
||
960 | * 3. The referenced data structure has already been exposed to |
||
961 | * readers either at compile time or via rcu_assign_pointer() -and- |
||
962 | * a. You have not made -any- reader-visible changes to |
||
963 | * this structure since then -or- |
||
964 | * b. It is OK for readers accessing this structure from its |
||
965 | * new location to see the old state of the structure. (For |
||
966 | * example, the changes were to statistical counters or to |
||
967 | * other state where exact synchronization is not required.) |
||
968 | * |
||
969 | * Failure to follow these rules governing use of RCU_INIT_POINTER() will |
||
970 | * result in impossible-to-diagnose memory corruption. As in the structures |
||
971 | * will look OK in crash dumps, but any concurrent RCU readers might |
||
972 | * see pre-initialized values of the referenced data structure. So |
||
973 | * please be very careful how you use RCU_INIT_POINTER()!!! |
||
974 | * |
||
975 | * If you are creating an RCU-protected linked structure that is accessed |
||
976 | * by a single external-to-structure RCU-protected pointer, then you may |
||
977 | * use RCU_INIT_POINTER() to initialize the internal RCU-protected |
||
978 | * pointers, but you must use rcu_assign_pointer() to initialize the |
||
979 | * external-to-structure pointer -after- you have completely initialized |
||
980 | * the reader-accessible portions of the linked structure. |
||
981 | * |
||
982 | * Note that unlike rcu_assign_pointer(), RCU_INIT_POINTER() provides no |
||
983 | * ordering guarantees for either the CPU or the compiler. |
||
984 | */ |
||
985 | #define RCU_INIT_POINTER(p, v) \ |
||
986 | do { \ |
||
987 | rcu_dereference_sparse(p, __rcu); \ |
||
988 | p = RCU_INITIALIZER(v); \ |
||
989 | } while (0) |
||
990 | |||
991 | /** |
||
992 | * RCU_POINTER_INITIALIZER() - statically initialize an RCU protected pointer |
||
993 | * |
||
994 | * GCC-style initialization for an RCU-protected pointer in a structure field. |
||
995 | */ |
||
996 | #define RCU_POINTER_INITIALIZER(p, v) \ |
||
997 | .p = RCU_INITIALIZER(v) |
||
998 | |||
999 | /* |
||
1000 | * Does the specified offset indicate that the corresponding rcu_head |
||
1001 | * structure can be handled by kfree_rcu()? |
||
1002 | */ |
||
1003 | #define __is_kfree_rcu_offset(offset) ((offset) < 4096) |
||
1004 | |||
1005 | /* |
||
1006 | * Helper macro for kfree_rcu() to prevent argument-expansion eyestrain. |
||
1007 | */ |
||
1008 | #define __kfree_rcu(head, offset) \ |
||
1009 | do { \ |
||
1010 | BUILD_BUG_ON(!__is_kfree_rcu_offset(offset)); \ |
||
1011 | kfree_call_rcu(head, (void (*)(struct rcu_head *))(unsigned long)(offset)); \ |
||
1012 | } while (0) |
||
1013 | |||
1014 | /** |
||
1015 | * kfree_rcu() - kfree an object after a grace period. |
||
1016 | * @ptr: pointer to kfree |
||
1017 | * @rcu_head: the name of the struct rcu_head within the type of @ptr. |
||
1018 | * |
||
1019 | * Many rcu callbacks functions just call kfree() on the base structure. |
||
1020 | * These functions are trivial, but their size adds up, and furthermore |
||
1021 | * when they are used in a kernel module, that module must invoke the |
||
1022 | * high-latency rcu_barrier() function at module-unload time. |
||
1023 | * |
||
1024 | * The kfree_rcu() function handles this issue. Rather than encoding a |
||
1025 | * function address in the embedded rcu_head structure, kfree_rcu() instead |
||
1026 | * encodes the offset of the rcu_head structure within the base structure. |
||
1027 | * Because the functions are not allowed in the low-order 4096 bytes of |
||
1028 | * kernel virtual memory, offsets up to 4095 bytes can be accommodated. |
||
1029 | * If the offset is larger than 4095 bytes, a compile-time error will |
||
1030 | * be generated in __kfree_rcu(). If this error is triggered, you can |
||
1031 | * either fall back to use of call_rcu() or rearrange the structure to |
||
1032 | * position the rcu_head structure into the first 4096 bytes. |
||
1033 | * |
||
1034 | * Note that the allowable offset might decrease in the future, for example, |
||
1035 | * to allow something like kmem_cache_free_rcu(). |
||
1036 | * |
||
1037 | * The BUILD_BUG_ON check must not involve any function calls, hence the |
||
1038 | * checks are done in macros here. |
||
1039 | */ |
||
1040 | #define kfree_rcu(ptr, rcu_head) \ |
||
1041 | __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head)) |
||
1042 | |||
6082 | serge | 1043 | #ifdef CONFIG_TINY_RCU |
1044 | static inline int rcu_needs_cpu(u64 basemono, u64 *nextevt) |
||
5270 | serge | 1045 | { |
6082 | serge | 1046 | *nextevt = KTIME_MAX; |
5270 | serge | 1047 | return 0; |
1048 | } |
||
6082 | serge | 1049 | #endif /* #ifdef CONFIG_TINY_RCU */ |
5270 | serge | 1050 | |
1051 | #if defined(CONFIG_RCU_NOCB_CPU_ALL) |
||
1052 | static inline bool rcu_is_nocb_cpu(int cpu) { return true; } |
||
1053 | #elif defined(CONFIG_RCU_NOCB_CPU) |
||
1054 | bool rcu_is_nocb_cpu(int cpu); |
||
1055 | #else |
||
1056 | static inline bool rcu_is_nocb_cpu(int cpu) { return false; } |
||
1057 | #endif |
||
1058 | |||
1059 | |||
1060 | /* Only for use by adaptive-ticks code. */ |
||
1061 | #ifdef CONFIG_NO_HZ_FULL_SYSIDLE |
||
1062 | bool rcu_sys_is_idle(void); |
||
1063 | void rcu_sysidle_force_exit(void); |
||
1064 | #else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ |
||
1065 | |||
1066 | static inline bool rcu_sys_is_idle(void) |
||
1067 | { |
||
1068 | return false; |
||
1069 | } |
||
1070 | |||
1071 | static inline void rcu_sysidle_force_exit(void) |
||
1072 | { |
||
1073 | } |
||
1074 | |||
1075 | #endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ |
||
1076 | |||
1077 | |||
1078 | #endif /* __LINUX_RCUPDATE_H */>>> |