1 | /* |
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2 | * readlock.c - kernel readlock synchronization |
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3 | * |
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4 | * Author Alain Greiner (2016} |
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5 | * |
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6 | * Copyright (c) UPMC Sorbonne Universites |
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7 | * |
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8 | * This file is part of ALMOS-MKH. |
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9 | * |
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10 | * ALMOS-MKH is free software; you can redistribute it and/or modify it |
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11 | * under the terms of the GNU General Public License as published by |
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12 | * the Free Software Foundation; version 2.0 of the License. |
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13 | * |
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14 | * ALMOS-MKH is distributed in the hope that it will be useful, but |
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15 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
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16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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17 | * General Public License for more details. |
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18 | * |
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19 | * You should have received a copy of the GNU General Public License |
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20 | * along with ALMOS-MKH; if not, write to the Free Software Foundation, |
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21 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
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22 | */ |
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23 | |
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24 | #include <almos_config.h> |
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25 | #include <hal_types.h> |
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26 | #include <hal_atomic.h> |
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27 | #include <hal_special.h> |
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28 | #include <hal_irqmask.h> |
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29 | #include <thread.h> |
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30 | #include <scheduler.h> |
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31 | #include <printk.h> |
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32 | #include <readlock.h> |
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33 | |
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34 | /////////////////////////////////////// |
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35 | void readlock_init( readlock_t * lock ) |
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36 | { |
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37 | lock->taken = 0; |
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38 | lock->count = 0; |
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39 | lock->owner = NULL; |
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40 | } |
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41 | |
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42 | ////////////////////////////////////////// |
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43 | void readlock_rd_lock( readlock_t * lock ) |
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44 | { |
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45 | uint32_t mode; |
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46 | volatile uint32_t taken; |
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47 | thread_t * this = CURRENT_THREAD; |
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48 | bool_t isAtomic = false; |
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49 | |
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50 | // disable IRQs |
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51 | hal_disable_irq( &mode ); |
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52 | |
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53 | // loop to take the lock against concurrent write |
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54 | while( isAtomic == false ) |
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55 | { |
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56 | // check lock value with a simple read |
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57 | taken = lock->taken; |
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58 | if( taken != 0 ) continue; |
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59 | |
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60 | // try to tomically take the lock |
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61 | isAtomic = hal_atomic_cas( &lock->taken , 0 , 1 ); |
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62 | } |
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63 | |
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64 | // increment count |
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65 | lock->count++; |
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66 | |
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67 | // sync |
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68 | hal_wbflush(); |
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69 | |
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70 | // release lock to support several parallel read access |
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71 | lock->taken = 0; |
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72 | |
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73 | // update calling thread locks count |
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74 | this->local_locks++; |
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75 | |
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76 | // enable IRQs |
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77 | hal_restore_irq( mode ); |
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78 | } |
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79 | |
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80 | //////////////////////////////////////////// |
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81 | void readlock_rd_unlock( readlock_t * lock ) |
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82 | { |
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83 | uint32_t mode; |
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84 | thread_t * this = CURRENT_THREAD; |
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85 | |
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86 | // disable IRQs |
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87 | hal_disable_irq( &mode ); |
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88 | |
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89 | hal_atomic_dec( &lock->count ); |
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90 | this->local_locks--; |
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91 | |
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92 | // enable IRQs |
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93 | hal_restore_irq( mode ); |
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94 | } |
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95 | |
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96 | ////////////////////////////////////////// |
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97 | void readlock_wr_lock( readlock_t * lock ) |
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98 | { |
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99 | uint32_t mode; |
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100 | volatile uint32_t taken; |
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101 | volatile bool_t isAtomic = false; |
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102 | volatile bool_t noReader = false; |
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103 | thread_t * this = CURRENT_THREAD; |
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104 | |
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105 | // disable IRQs |
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106 | hal_disable_irq( &mode ); |
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107 | |
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108 | // loop to take the lock |
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109 | while( isAtomic == false ) |
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110 | { |
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111 | // check lock state with a simple read |
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112 | taken = lock->taken; |
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113 | if( taken != 0 ) continue; |
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114 | |
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115 | // try to atomically take the lock if not already taken |
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116 | isAtomic = hal_atomic_cas( &lock->taken , 0 , 1 ); |
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117 | } |
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118 | |
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119 | // wait completion of read accesses |
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120 | while( noReader == false ) |
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121 | { |
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122 | noReader = ( lock->count == 0 ); |
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123 | } |
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124 | |
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125 | lock->owner = this; |
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126 | this->local_locks++; |
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127 | |
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128 | // enable IRQs |
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129 | hal_restore_irq( mode ); |
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130 | } |
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131 | |
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132 | //////////////////////////////////////////// |
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133 | void readlock_wr_unlock( readlock_t * lock ) |
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134 | { |
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135 | uint32_t mode; |
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136 | thread_t * this = CURRENT_THREAD; |
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137 | |
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138 | // disable IRQs |
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139 | hal_disable_irq( &mode ); |
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140 | |
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141 | lock->owner = NULL; |
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142 | lock->taken = 0; |
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143 | this->local_locks--; |
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144 | |
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145 | // enable IRQs |
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146 | hal_restore_irq( mode ); |
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147 | } |
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148 | |
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