1 | // |
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2 | // Cforall Version 1.0.0 Copyright (C) 2021 University of Waterloo |
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3 | // |
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4 | // The contents of this file are covered under the licence agreement in the |
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5 | // file "LICENCE" distributed with Cforall. |
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6 | // |
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7 | // channel.hfa -- LIBCFATHREAD |
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8 | // Runtime locks that used with the runtime thread system. |
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9 | // |
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10 | // Author : Colby Alexander Parsons |
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11 | // Created On : Thu Jan 21 19:46:50 2022 |
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12 | // Last Modified By : |
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13 | // Last Modified On : |
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14 | // Update Count : |
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15 | // |
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16 | |
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17 | #pragma once |
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18 | |
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19 | #include <locks.hfa> |
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20 | #include <list.hfa> |
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21 | #include "select.hfa" |
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22 | |
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23 | // returns true if woken due to shutdown |
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24 | // blocks thread on list and releases passed lock |
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25 | static inline bool block( dlist( select_node ) & queue, void * elem_ptr, go_mutex & lock ) { |
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26 | select_node sn{ active_thread(), elem_ptr }; |
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27 | insert_last( queue, sn ); |
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28 | unlock( lock ); |
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29 | park(); |
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30 | return sn.extra == 0p; |
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31 | } |
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32 | |
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33 | // Waituntil support (un)register_select helper routine |
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34 | // Sets select node avail if not special OR case and then unlocks |
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35 | static inline void __set_avail_then_unlock( select_node & node, go_mutex & mutex_lock ) { |
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36 | if ( node.park_counter ) __make_select_node_available( node ); |
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37 | unlock( mutex_lock ); |
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38 | } |
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39 | |
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40 | // void * used for some fields since exceptions don't work with parametric polymorphism currently |
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41 | exception channel_closed { |
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42 | // on failed insert elem is a ptr to the element attempting to be inserted |
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43 | // on failed remove elem ptr is 0p |
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44 | // on resumption of a failed insert this elem will be inserted |
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45 | // so a user may modify it in the resumption handler |
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46 | void * elem; |
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47 | |
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48 | // pointer to chan that is closed |
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49 | void * closed_chan; |
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50 | }; |
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51 | vtable(channel_closed) channel_closed_vt; |
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52 | |
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53 | // #define CHAN_STATS // define this to get channel stats printed in dtor |
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54 | |
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55 | forall( T ) { |
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56 | |
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57 | struct __attribute__((aligned(128))) channel { |
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58 | size_t size, front, back, count; |
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59 | T * buffer; |
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60 | dlist( select_node ) prods, cons; // lists of blocked threads |
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61 | go_mutex mutex_lock; // MX lock |
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62 | bool closed; // indicates channel close/open |
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63 | #ifdef CHAN_STATS |
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64 | size_t p_blocks, p_ops, c_blocks, c_ops; // counts total ops and ops resulting in a blocked thd |
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65 | #endif |
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66 | }; |
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67 | |
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68 | static inline void ?{}( channel(T) &c, size_t _size ) with(c) { |
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69 | size = _size; |
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70 | front = back = count = 0; |
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71 | if ( size != 0 ) buffer = aalloc( size ); |
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72 | prods{}; |
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73 | cons{}; |
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74 | mutex_lock{}; |
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75 | closed = false; |
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76 | #ifdef CHAN_STATS |
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77 | p_blocks = 0; |
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78 | p_ops = 0; |
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79 | c_blocks = 0; |
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80 | c_ops = 0; |
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81 | #endif |
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82 | } |
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83 | |
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84 | static inline void ?{}( channel(T) &c ){ ((channel(T) &)c){ 0 }; } |
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85 | static inline void ^?{}( channel(T) &c ) with(c) { |
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86 | #ifdef CHAN_STATS |
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87 | printf("Channel %p Blocks: %lu,\t\tOperations: %lu,\t%.2f%% of ops blocked\n", &c, p_blocks + c_blocks, p_ops + c_ops, ((double)p_blocks + c_blocks)/(p_ops + c_ops) * 100); |
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88 | printf("Channel %p Consumer Blocks: %lu,\tConsumer Ops: %lu,\t%.2f%% of Consumer ops blocked\n", &c, p_blocks, p_ops, ((double)p_blocks)/p_ops * 100); |
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89 | printf("Channel %p Producer Blocks: %lu,\tProducer Ops: %lu,\t%.2f%% of Producer ops blocked\n", &c, c_blocks, c_ops, ((double)c_blocks)/c_ops * 100); |
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90 | #endif |
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91 | verifyf( __handle_waituntil_OR( cons ) || __handle_waituntil_OR( prods ) || cons`isEmpty && prods`isEmpty, |
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92 | "Attempted to delete channel with waiting threads (Deadlock).\n" ); |
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93 | if ( size != 0 ) delete( buffer ); |
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94 | } |
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95 | static inline size_t get_count( channel(T) & chan ) with(chan) { return __atomic_load_n( &count, __ATOMIC_RELAXED ); } |
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96 | static inline size_t get_size( channel(T) & chan ) with(chan) { return __atomic_load_n( &size, __ATOMIC_RELAXED ); } |
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97 | static inline bool has_waiters( channel(T) & chan ) with(chan) { return !cons`isEmpty || !prods`isEmpty; } |
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98 | static inline bool has_waiting_consumers( channel(T) & chan ) with(chan) { return !cons`isEmpty; } |
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99 | static inline bool has_waiting_producers( channel(T) & chan ) with(chan) { return !prods`isEmpty; } |
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100 | |
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101 | // closes the channel and notifies all blocked threads |
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102 | static inline void close( channel(T) & chan ) with(chan) { |
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103 | lock( mutex_lock ); |
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104 | closed = true; |
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105 | |
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106 | // flush waiting consumers and producers |
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107 | while ( has_waiting_consumers( chan ) ) { |
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108 | if( !__handle_waituntil_OR( cons ) ) // ensure we only signal special OR case threads when they win the race |
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109 | break; // if __handle_waituntil_OR returns false cons is empty so break |
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110 | cons`first.extra = 0p; |
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111 | wake_one( cons ); |
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112 | } |
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113 | while ( has_waiting_producers( chan ) ) { |
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114 | if( !__handle_waituntil_OR( prods ) ) // ensure we only signal special OR case threads when they win the race |
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115 | break; // if __handle_waituntil_OR returns false prods is empty so break |
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116 | prods`first.extra = 0p; |
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117 | wake_one( prods ); |
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118 | } |
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119 | unlock(mutex_lock); |
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120 | } |
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121 | |
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122 | static inline void is_closed( channel(T) & chan ) with(chan) { return closed; } |
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123 | |
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124 | // used to hand an element to a blocked consumer and signal it |
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125 | static inline void __cons_handoff( channel(T) & chan, T & elem ) with(chan) { |
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126 | memcpy( cons`first.extra, (void *)&elem, sizeof(T) ); // do waiting consumer work |
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127 | wake_one( cons ); |
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128 | } |
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129 | |
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130 | // used to hand an element to a blocked producer and signal it |
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131 | static inline void __prods_handoff( channel(T) & chan, T & retval ) with(chan) { |
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132 | memcpy( (void *)&retval, prods`first.extra, sizeof(T) ); |
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133 | wake_one( prods ); |
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134 | } |
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135 | |
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136 | static inline void flush( channel(T) & chan, T elem ) with(chan) { |
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137 | lock( mutex_lock ); |
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138 | while ( count == 0 && !cons`isEmpty ) { |
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139 | __cons_handoff( chan, elem ); |
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140 | } |
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141 | unlock( mutex_lock ); |
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142 | } |
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143 | |
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144 | // handles buffer insert |
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145 | static inline void __buf_insert( channel(T) & chan, T & elem ) with(chan) { |
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146 | memcpy( (void *)&buffer[back], (void *)&elem, sizeof(T) ); |
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147 | count += 1; |
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148 | back++; |
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149 | if ( back == size ) back = 0; |
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150 | } |
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151 | |
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152 | // needed to avoid an extra copy in closed case |
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153 | static inline bool __internal_try_insert( channel(T) & chan, T & elem ) with(chan) { |
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154 | lock( mutex_lock ); |
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155 | #ifdef CHAN_STATS |
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156 | p_ops++; |
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157 | #endif |
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158 | |
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159 | ConsEmpty: if ( !cons`isEmpty ) { |
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160 | if ( !__handle_waituntil_OR( cons ) ) break ConsEmpty; |
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161 | __cons_handoff( chan, elem ); |
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162 | unlock( mutex_lock ); |
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163 | return true; |
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164 | } |
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165 | |
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166 | if ( count == size ) { unlock( mutex_lock ); return false; } |
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167 | |
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168 | __buf_insert( chan, elem ); |
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169 | unlock( mutex_lock ); |
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170 | return true; |
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171 | } |
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172 | |
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173 | // attempts a nonblocking insert |
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174 | // returns true if insert was successful, false otherwise |
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175 | static inline bool try_insert( channel(T) & chan, T elem ) { return __internal_try_insert( chan, elem ); } |
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176 | |
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177 | // handles closed case of insert routine |
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178 | static inline void __closed_insert( channel(T) & chan, T & elem ) with(chan) { |
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179 | channel_closed except{ &channel_closed_vt, &elem, &chan }; |
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180 | throwResume except; // throw closed resumption |
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181 | if ( !__internal_try_insert( chan, elem ) ) throw except; // if try to insert fails (would block), throw termination |
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182 | } |
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183 | |
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184 | static inline void insert( channel(T) & chan, T elem ) with(chan) { |
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185 | // check for close before acquire mx |
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186 | if ( unlikely(closed) ) { |
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187 | __closed_insert( chan, elem ); |
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188 | return; |
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189 | } |
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190 | |
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191 | lock( mutex_lock ); |
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192 | |
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193 | #ifdef CHAN_STATS |
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194 | if ( !closed ) p_ops++; |
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195 | #endif |
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196 | |
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197 | // if closed handle |
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198 | if ( unlikely(closed) ) { |
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199 | unlock( mutex_lock ); |
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200 | __closed_insert( chan, elem ); |
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201 | return; |
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202 | } |
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203 | |
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204 | // buffer count must be zero if cons are blocked (also handles zero-size case) |
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205 | ConsEmpty: if ( !cons`isEmpty ) { |
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206 | if ( !__handle_waituntil_OR( cons ) ) break ConsEmpty; |
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207 | __cons_handoff( chan, elem ); |
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208 | unlock( mutex_lock ); |
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209 | return; |
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210 | } |
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211 | |
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212 | // wait if buffer is full, work will be completed by someone else |
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213 | if ( count == size ) { |
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214 | #ifdef CHAN_STATS |
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215 | p_blocks++; |
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216 | #endif |
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217 | |
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218 | // check for if woken due to close |
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219 | if ( unlikely( block( prods, &elem, mutex_lock ) ) ) |
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220 | __closed_insert( chan, elem ); |
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221 | return; |
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222 | } // if |
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223 | |
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224 | __buf_insert( chan, elem ); |
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225 | unlock( mutex_lock ); |
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226 | } |
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227 | |
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228 | // does the buffer remove and potentially does waiting producer work |
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229 | static inline void __do_remove( channel(T) & chan, T & retval ) with(chan) { |
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230 | memcpy( (void *)&retval, (void *)&buffer[front], sizeof(T) ); |
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231 | count -= 1; |
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232 | front = (front + 1) % size; |
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233 | if (count == size - 1 && !prods`isEmpty ) { |
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234 | if ( !__handle_waituntil_OR( prods ) ) return; |
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235 | __buf_insert( chan, *(T *)prods`first.extra ); // do waiting producer work |
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236 | wake_one( prods ); |
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237 | } |
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238 | } |
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239 | |
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240 | // needed to avoid an extra copy in closed case and single return val case |
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241 | static inline bool __internal_try_remove( channel(T) & chan, T & retval ) with(chan) { |
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242 | lock( mutex_lock ); |
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243 | #ifdef CHAN_STATS |
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244 | c_ops++; |
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245 | #endif |
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246 | |
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247 | ZeroSize: if ( size == 0 && !prods`isEmpty ) { |
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248 | if ( !__handle_waituntil_OR( prods ) ) break ZeroSize; |
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249 | __prods_handoff( chan, retval ); |
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250 | unlock( mutex_lock ); |
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251 | return true; |
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252 | } |
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253 | |
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254 | if ( count == 0 ) { unlock( mutex_lock ); return false; } |
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255 | |
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256 | __do_remove( chan, retval ); |
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257 | unlock( mutex_lock ); |
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258 | return true; |
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259 | } |
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260 | |
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261 | // attempts a nonblocking remove |
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262 | // returns [T, true] if insert was successful |
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263 | // returns [T, false] if insert was successful (T uninit) |
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264 | static inline [T, bool] try_remove( channel(T) & chan ) { |
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265 | T retval; |
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266 | bool success = __internal_try_remove( chan, retval ); |
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267 | return [ retval, success ]; |
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268 | } |
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269 | |
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270 | static inline T try_remove( channel(T) & chan ) { |
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271 | T retval; |
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272 | __internal_try_remove( chan, retval ); |
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273 | return retval; |
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274 | } |
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275 | |
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276 | // handles closed case of insert routine |
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277 | static inline void __closed_remove( channel(T) & chan, T & retval ) with(chan) { |
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278 | channel_closed except{ &channel_closed_vt, 0p, &chan }; |
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279 | throwResume except; // throw resumption |
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280 | if ( !__internal_try_remove( chan, retval ) ) throw except; // if try to remove fails (would block), throw termination |
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281 | } |
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282 | |
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283 | static inline T remove( channel(T) & chan ) with(chan) { |
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284 | T retval; |
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285 | if ( unlikely(closed) ) { |
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286 | __closed_remove( chan, retval ); |
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287 | return retval; |
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288 | } |
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289 | lock( mutex_lock ); |
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290 | |
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291 | #ifdef CHAN_STATS |
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292 | if ( !closed ) c_ops++; |
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293 | #endif |
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294 | |
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295 | if ( unlikely(closed) ) { |
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296 | unlock( mutex_lock ); |
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297 | __closed_remove( chan, retval ); |
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298 | return retval; |
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299 | } |
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300 | |
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301 | // have to check for the zero size channel case |
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302 | ZeroSize: if ( size == 0 && !prods`isEmpty ) { |
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303 | if ( !__handle_waituntil_OR( prods ) ) break ZeroSize; |
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304 | __prods_handoff( chan, retval ); |
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305 | unlock( mutex_lock ); |
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306 | return retval; |
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307 | } |
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308 | |
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309 | // wait if buffer is empty, work will be completed by someone else |
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310 | if ( count == 0 ) { |
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311 | #ifdef CHAN_STATS |
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312 | c_blocks++; |
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313 | #endif |
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314 | // check for if woken due to close |
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315 | if ( unlikely( block( cons, &retval, mutex_lock ) ) ) |
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316 | __closed_remove( chan, retval ); |
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317 | return retval; |
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318 | } |
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319 | |
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320 | // Remove from buffer |
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321 | __do_remove( chan, retval ); |
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322 | unlock( mutex_lock ); |
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323 | return retval; |
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324 | } |
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325 | |
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326 | /////////////////////////////////////////////////////////////////////////////////////////// |
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327 | // The following is support for waituntil (select) statements |
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328 | /////////////////////////////////////////////////////////////////////////////////////////// |
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329 | static inline bool unregister_chan( channel(T) & chan, select_node & node ) with(chan) { |
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330 | if ( !node`isListed && !node.park_counter ) return false; // handle special OR case |
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331 | lock( mutex_lock ); |
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332 | if ( node`isListed ) { // op wasn't performed |
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333 | remove( node ); |
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334 | unlock( mutex_lock ); |
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335 | return false; |
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336 | } |
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337 | unlock( mutex_lock ); |
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338 | |
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339 | // only return true when not special OR case, not exceptional calse and status is SAT |
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340 | return ( node.extra == 0p || !node.park_counter ) ? false : *node.clause_status == __SELECT_SAT; |
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341 | } |
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342 | |
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343 | // type used by select statement to capture a chan read as the selected operation |
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344 | struct chan_read { |
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345 | T & ret; |
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346 | channel(T) & chan; |
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347 | }; |
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348 | |
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349 | static inline void ?{}( chan_read(T) & cr, channel(T) & chan, T & ret ) { |
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350 | &cr.chan = &chan; |
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351 | &cr.ret = &ret; |
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352 | } |
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353 | static inline chan_read(T) ?<<?( T & ret, channel(T) & chan ) { chan_read(T) cr{ chan, ret }; return cr; } |
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354 | |
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355 | static inline void __handle_select_closed_read( chan_read(T) & this, select_node & node ) with(this.chan, this) { |
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356 | __closed_remove( chan, ret ); |
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357 | // if we get here then the insert succeeded |
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358 | __make_select_node_available( node ); |
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359 | } |
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360 | |
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361 | static inline bool register_select( chan_read(T) & this, select_node & node ) with(this.chan, this) { |
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362 | lock( mutex_lock ); |
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363 | node.extra = &ret; // set .extra so that if it == 0p later in on_selected it is due to channel close |
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364 | |
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365 | #ifdef CHAN_STATS |
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366 | if ( !closed ) c_ops++; |
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367 | #endif |
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368 | |
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369 | if ( !node.park_counter ) { |
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370 | // are we special case OR and front of cons is also special case OR |
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371 | if ( !unlikely(closed) && !prods`isEmpty && prods`first.clause_status && !prods`first.park_counter ) { |
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372 | if ( !__make_select_node_pending( node ) ) { |
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373 | unlock( mutex_lock ); |
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374 | return false; |
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375 | } |
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376 | |
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377 | if ( __handle_waituntil_OR( prods ) ) { |
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378 | __prods_handoff( chan, ret ); |
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379 | __make_select_node_sat( node ); // need to to mark SAT now that we know operation is done or else threads could get stuck in __mark_select_node |
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380 | unlock( mutex_lock ); |
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381 | return true; |
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382 | } |
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383 | __make_select_node_unsat( node ); |
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384 | } |
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385 | // check if we can complete operation. If so race to establish winner in special OR case |
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386 | if ( count != 0 || !prods`isEmpty || unlikely(closed) ) { |
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387 | if ( !__make_select_node_available( node ) ) { // we didn't win the race so give up on registering |
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388 | unlock( mutex_lock ); |
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389 | return false; |
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390 | } |
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391 | } |
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392 | } |
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393 | |
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394 | if ( unlikely(closed) ) { |
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395 | unlock( mutex_lock ); |
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396 | __handle_select_closed_read( this, node ); |
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397 | return true; |
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398 | } |
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399 | |
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400 | // have to check for the zero size channel case |
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401 | ZeroSize: if ( size == 0 && !prods`isEmpty ) { |
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402 | if ( !__handle_waituntil_OR( prods ) ) break ZeroSize; |
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403 | __prods_handoff( chan, ret ); |
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404 | __set_avail_then_unlock( node, mutex_lock ); |
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405 | return true; |
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406 | } |
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407 | |
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408 | // wait if buffer is empty, work will be completed by someone else |
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409 | if ( count == 0 ) { |
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410 | #ifdef CHAN_STATS |
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411 | c_blocks++; |
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412 | #endif |
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413 | |
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414 | insert_last( cons, node ); |
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415 | unlock( mutex_lock ); |
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416 | return false; |
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417 | } |
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418 | |
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419 | // Remove from buffer |
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420 | __do_remove( chan, ret ); |
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421 | __set_avail_then_unlock( node, mutex_lock ); |
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422 | return true; |
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423 | } |
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424 | static inline bool unregister_select( chan_read(T) & this, select_node & node ) { return unregister_chan( this.chan, node ); } |
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425 | static inline bool on_selected( chan_read(T) & this, select_node & node ) with(this) { |
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426 | if ( node.extra == 0p ) // check if woken up due to closed channel |
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427 | __closed_remove( chan, ret ); |
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428 | // This is only reachable if not closed or closed exception was handled |
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429 | return true; |
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430 | } |
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431 | |
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432 | // type used by select statement to capture a chan write as the selected operation |
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433 | struct chan_write { |
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434 | T elem; |
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435 | channel(T) & chan; |
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436 | }; |
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437 | |
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438 | static inline void ?{}( chan_write(T) & cw, channel(T) & chan, T elem ) { |
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439 | &cw.chan = &chan; |
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440 | memcpy( (void *)&cw.elem, (void *)&elem, sizeof(T) ); |
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441 | } |
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442 | static inline chan_write(T) ?>>?( T elem, channel(T) & chan ) { chan_write(T) cw{ chan, elem }; return cw; } |
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443 | |
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444 | static inline void __handle_select_closed_write( chan_write(T) & this, select_node & node ) with(this.chan, this) { |
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445 | __closed_insert( chan, elem ); |
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446 | // if we get here then the insert succeeded |
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447 | __make_select_node_available( node ); |
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448 | } |
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449 | |
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450 | static inline bool register_select( chan_write(T) & this, select_node & node ) with(this.chan, this) { |
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451 | lock( mutex_lock ); |
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452 | node.extra = &elem; // set .extra so that if it == 0p later in on_selected it is due to channel close |
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453 | |
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454 | #ifdef CHAN_STATS |
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455 | if ( !closed ) p_ops++; |
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456 | #endif |
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457 | |
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458 | // special OR case handling |
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459 | if ( !node.park_counter ) { |
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460 | // are we special case OR and front of cons is also special case OR |
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461 | if ( !unlikely(closed) && !cons`isEmpty && cons`first.clause_status && !cons`first.park_counter ) { |
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462 | if ( !__make_select_node_pending( node ) ) { |
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463 | unlock( mutex_lock ); |
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464 | return false; |
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465 | } |
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466 | |
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467 | if ( __handle_waituntil_OR( cons ) ) { |
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468 | __cons_handoff( chan, elem ); |
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469 | __make_select_node_sat( node ); // need to to mark SAT now that we know operation is done or else threads could get stuck in __mark_select_node |
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470 | unlock( mutex_lock ); |
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471 | return true; |
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472 | } |
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473 | __make_select_node_unsat( node ); |
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474 | } |
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475 | // check if we can complete operation. If so race to establish winner in special OR case |
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476 | if ( count != size || !cons`isEmpty || unlikely(closed) ) { |
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477 | if ( !__make_select_node_available( node ) ) { // we didn't win the race so give up on registering |
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478 | unlock( mutex_lock ); |
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479 | return false; |
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480 | } |
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481 | } |
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482 | } |
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483 | |
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484 | // if closed handle |
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485 | if ( unlikely(closed) ) { |
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486 | unlock( mutex_lock ); |
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487 | __handle_select_closed_write( this, node ); |
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488 | return true; |
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489 | } |
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490 | |
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491 | // handle blocked consumer case via handoff (buffer is implicitly empty) |
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492 | ConsEmpty: if ( !cons`isEmpty ) { |
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493 | if ( !__handle_waituntil_OR( cons ) ) break ConsEmpty; |
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494 | __cons_handoff( chan, elem ); |
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495 | __set_avail_then_unlock( node, mutex_lock ); |
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496 | return true; |
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497 | } |
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498 | |
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499 | // insert node in list if buffer is full, work will be completed by someone else |
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500 | if ( count == size ) { |
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501 | #ifdef CHAN_STATS |
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502 | p_blocks++; |
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503 | #endif |
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504 | |
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505 | insert_last( prods, node ); |
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506 | unlock( mutex_lock ); |
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507 | return false; |
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508 | } // if |
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509 | |
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510 | // otherwise carry out write either via normal insert |
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511 | __buf_insert( chan, elem ); |
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512 | __set_avail_then_unlock( node, mutex_lock ); |
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513 | return true; |
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514 | } |
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515 | static inline bool unregister_select( chan_write(T) & this, select_node & node ) { return unregister_chan( this.chan, node ); } |
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516 | |
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517 | static inline bool on_selected( chan_write(T) & this, select_node & node ) with(this) { |
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518 | if ( node.extra == 0p ) // check if woken up due to closed channel |
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519 | __closed_insert( chan, elem ); |
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520 | |
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521 | // This is only reachable if not closed or closed exception was handled |
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522 | return true; |
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523 | } |
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524 | |
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525 | } // forall( T ) |
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526 | |
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527 | |
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