| 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 blocks, operations; // 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 | blocks = 0;
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| 78 | operations = 0;
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| 79 | #endif
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| 80 | }
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| 81 |
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| 82 | static inline void ?{}( channel(T) &c ){ ((channel(T) &)c){ 0 }; }
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| 83 | static inline void ^?{}( channel(T) &c ) with(c) {
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| 84 | #ifdef CHAN_STATS
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| 85 | printf("Channel %p Blocks: %lu, Operations: %lu, %.2f%% of ops blocked\n", &c, blocks, operations, ((double)blocks)/operations * 100);
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| 86 | #endif
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| 87 | verifyf( cons`isEmpty && prods`isEmpty, "Attempted to delete channel with waiting threads (Deadlock).\n" );
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| 88 | if ( size != 0 ) delete( buffer );
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| 89 | }
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| 90 | static inline size_t get_count( channel(T) & chan ) with(chan) { return __atomic_load_n( &count, __ATOMIC_RELAXED ); }
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| 91 | static inline size_t get_size( channel(T) & chan ) with(chan) { return __atomic_load_n( &size, __ATOMIC_RELAXED ); }
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| 92 | static inline bool has_waiters( channel(T) & chan ) with(chan) { return !cons`isEmpty || !prods`isEmpty; }
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| 93 | static inline bool has_waiting_consumers( channel(T) & chan ) with(chan) { return !cons`isEmpty; }
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| 94 | static inline bool has_waiting_producers( channel(T) & chan ) with(chan) { return !prods`isEmpty; }
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| 95 |
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| 96 | // closes the channel and notifies all blocked threads
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| 97 | static inline void close( channel(T) & chan ) with(chan) {
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| 98 | lock( mutex_lock );
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| 99 | closed = true;
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| 100 |
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| 101 | // flush waiting consumers and producers
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| 102 | while ( has_waiting_consumers( chan ) ) {
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| 103 | if( !__handle_waituntil_OR( cons ) ) // ensure we only signal special OR case threads when they win the race
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| 104 | break; // if __handle_waituntil_OR returns false cons is empty so break
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| 105 | cons`first.extra = 0p;
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| 106 | wake_one( cons );
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| 107 | }
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| 108 | while ( has_waiting_producers( chan ) ) {
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| 109 | if( !__handle_waituntil_OR( prods ) ) // ensure we only signal special OR case threads when they win the race
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| 110 | break; // if __handle_waituntil_OR returns false prods is empty so break
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| 111 | prods`first.extra = 0p;
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| 112 | wake_one( prods );
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| 113 | }
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| 114 | unlock(mutex_lock);
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| 115 | }
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| 116 |
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| 117 | static inline void is_closed( channel(T) & chan ) with(chan) { return closed; }
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| 118 |
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| 119 | // used to hand an element to a blocked consumer and signal it
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| 120 | static inline void __cons_handoff( channel(T) & chan, T & elem ) with(chan) {
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| 121 | memcpy( cons`first.extra, (void *)&elem, sizeof(T) ); // do waiting consumer work
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| 122 | wake_one( cons );
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| 123 | }
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| 124 |
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| 125 | // used to hand an element to a blocked producer and signal it
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| 126 | static inline void __prods_handoff( channel(T) & chan, T & retval ) with(chan) {
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| 127 | memcpy( (void *)&retval, prods`first.extra, sizeof(T) );
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| 128 | wake_one( prods );
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| 129 | }
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| 130 |
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| 131 | static inline void flush( channel(T) & chan, T elem ) with(chan) {
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| 132 | lock( mutex_lock );
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| 133 | while ( count == 0 && !cons`isEmpty ) {
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| 134 | __cons_handoff( chan, elem );
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| 135 | }
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| 136 | unlock( mutex_lock );
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| 137 | }
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| 138 |
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| 139 | // handles buffer insert
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| 140 | static inline void __buf_insert( channel(T) & chan, T & elem ) with(chan) {
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| 141 | memcpy( (void *)&buffer[back], (void *)&elem, sizeof(T) );
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| 142 | count += 1;
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| 143 | back++;
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| 144 | if ( back == size ) back = 0;
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| 145 | }
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| 146 |
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| 147 | // needed to avoid an extra copy in closed case
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| 148 | static inline bool __internal_try_insert( channel(T) & chan, T & elem ) with(chan) {
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| 149 | lock( mutex_lock );
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| 150 | #ifdef CHAN_STATS
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| 151 | operations++;
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| 152 | #endif
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| 153 |
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| 154 | ConsEmpty: if ( !cons`isEmpty ) {
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| 155 | if ( !__handle_waituntil_OR( cons ) ) break ConsEmpty;
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| 156 | __cons_handoff( chan, elem );
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| 157 | unlock( mutex_lock );
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| 158 | return true;
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| 159 | }
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| 160 |
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| 161 | if ( count == size ) { unlock( mutex_lock ); return false; }
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| 162 |
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| 163 | __buf_insert( chan, elem );
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| 164 | unlock( mutex_lock );
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| 165 | return true;
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| 166 | }
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| 167 |
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| 168 | // attempts a nonblocking insert
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| 169 | // returns true if insert was successful, false otherwise
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| 170 | static inline bool try_insert( channel(T) & chan, T elem ) { return __internal_try_insert( chan, elem ); }
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| 171 |
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| 172 | // handles closed case of insert routine
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| 173 | static inline void __closed_insert( channel(T) & chan, T & elem ) with(chan) {
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| 174 | channel_closed except{ &channel_closed_vt, &elem, &chan };
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| 175 | throwResume except; // throw closed resumption
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| 176 | if ( !__internal_try_insert( chan, elem ) ) throw except; // if try to insert fails (would block), throw termination
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| 177 | }
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| 178 |
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| 179 | static inline void insert( channel(T) & chan, T elem ) with(chan) {
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| 180 | // check for close before acquire mx
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| 181 | if ( unlikely(closed) ) {
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| 182 | __closed_insert( chan, elem );
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| 183 | return;
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| 184 | }
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| 185 |
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| 186 | lock( mutex_lock );
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| 187 |
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| 188 | #ifdef CHAN_STATS
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| 189 | if ( !closed ) operations++;
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| 190 | #endif
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| 191 |
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| 192 | // if closed handle
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| 193 | if ( unlikely(closed) ) {
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| 194 | unlock( mutex_lock );
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| 195 | __closed_insert( chan, elem );
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| 196 | return;
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| 197 | }
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| 198 |
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| 199 | // buffer count must be zero if cons are blocked (also handles zero-size case)
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| 200 | ConsEmpty: if ( !cons`isEmpty ) {
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| 201 | if ( !__handle_waituntil_OR( cons ) ) break ConsEmpty;
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| 202 | __cons_handoff( chan, elem );
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| 203 | unlock( mutex_lock );
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| 204 | return;
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| 205 | }
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| 206 |
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| 207 | // wait if buffer is full, work will be completed by someone else
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| 208 | if ( count == size ) {
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| 209 | #ifdef CHAN_STATS
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| 210 | blocks++;
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| 211 | #endif
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| 212 |
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| 213 | // check for if woken due to close
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| 214 | if ( unlikely( block( prods, &elem, mutex_lock ) ) )
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| 215 | __closed_insert( chan, elem );
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| 216 | return;
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| 217 | } // if
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| 218 |
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| 219 | __buf_insert( chan, elem );
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| 220 | unlock( mutex_lock );
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| 221 | }
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| 222 |
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| 223 | // does the buffer remove and potentially does waiting producer work
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| 224 | static inline void __do_remove( channel(T) & chan, T & retval ) with(chan) {
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| 225 | memcpy( (void *)&retval, (void *)&buffer[front], sizeof(T) );
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| 226 | count -= 1;
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| 227 | front = (front + 1) % size;
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| 228 | if (count == size - 1 && !prods`isEmpty ) {
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| 229 | if ( !__handle_waituntil_OR( prods ) ) return;
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| 230 | __buf_insert( chan, *(T *)prods`first.extra ); // do waiting producer work
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| 231 | wake_one( prods );
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| 232 | }
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| 233 | }
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| 234 |
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| 235 | // needed to avoid an extra copy in closed case and single return val case
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| 236 | static inline bool __internal_try_remove( channel(T) & chan, T & retval ) with(chan) {
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| 237 | lock( mutex_lock );
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| 238 | #ifdef CHAN_STATS
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| 239 | operations++;
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| 240 | #endif
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| 241 |
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| 242 | ZeroSize: if ( size == 0 && !prods`isEmpty ) {
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| 243 | if ( !__handle_waituntil_OR( prods ) ) break ZeroSize;
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| 244 | __prods_handoff( chan, retval );
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| 245 | unlock( mutex_lock );
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| 246 | return true;
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| 247 | }
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| 248 |
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| 249 | if ( count == 0 ) { unlock( mutex_lock ); return false; }
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| 250 |
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| 251 | __do_remove( chan, retval );
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| 252 | unlock( mutex_lock );
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| 253 | return true;
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| 254 | }
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| 255 |
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| 256 | // attempts a nonblocking remove
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| 257 | // returns [T, true] if insert was successful
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| 258 | // returns [T, false] if insert was successful (T uninit)
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| 259 | static inline [T, bool] try_remove( channel(T) & chan ) {
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| 260 | T retval;
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| 261 | bool success = __internal_try_remove( chan, retval );
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| 262 | return [ retval, success ];
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| 263 | }
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| 264 |
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| 265 | static inline T try_remove( channel(T) & chan ) {
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| 266 | T retval;
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| 267 | __internal_try_remove( chan, retval );
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| 268 | return retval;
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| 269 | }
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| 270 |
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| 271 | // handles closed case of insert routine
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| 272 | static inline void __closed_remove( channel(T) & chan, T & retval ) with(chan) {
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| 273 | channel_closed except{ &channel_closed_vt, 0p, &chan };
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| 274 | throwResume except; // throw resumption
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| 275 | if ( !__internal_try_remove( chan, retval ) ) throw except; // if try to remove fails (would block), throw termination
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| 276 | }
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| 277 |
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| 278 | static inline T remove( channel(T) & chan ) with(chan) {
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| 279 | T retval;
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| 280 | if ( unlikely(closed) ) {
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| 281 | __closed_remove( chan, retval );
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| 282 | return retval;
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| 283 | }
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| 284 | lock( mutex_lock );
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| 285 |
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| 286 | #ifdef CHAN_STATS
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| 287 | if ( !closed ) operations++;
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| 288 | #endif
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| 289 |
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| 290 | if ( unlikely(closed) ) {
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| 291 | unlock( mutex_lock );
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| 292 | __closed_remove( chan, retval );
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| 293 | return retval;
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| 294 | }
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| 295 |
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| 296 | // have to check for the zero size channel case
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| 297 | ZeroSize: if ( size == 0 && !prods`isEmpty ) {
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| 298 | if ( !__handle_waituntil_OR( prods ) ) break ZeroSize;
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| 299 | __prods_handoff( chan, retval );
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| 300 | unlock( mutex_lock );
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| 301 | return retval;
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| 302 | }
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| 303 |
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| 304 | // wait if buffer is empty, work will be completed by someone else
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| 305 | if ( count == 0 ) {
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| 306 | #ifdef CHAN_STATS
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| 307 | blocks++;
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| 308 | #endif
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| 309 | // check for if woken due to close
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| 310 | if ( unlikely( block( cons, &retval, mutex_lock ) ) )
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| 311 | __closed_remove( chan, retval );
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| 312 | return retval;
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| 313 | }
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| 314 |
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| 315 | // Remove from buffer
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| 316 | __do_remove( chan, retval );
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| 317 | unlock( mutex_lock );
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| 318 | return retval;
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| 319 | }
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| 320 |
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| 321 | ///////////////////////////////////////////////////////////////////////////////////////////
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| 322 | // The following is support for waituntil (select) statements
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| 323 | ///////////////////////////////////////////////////////////////////////////////////////////
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| 324 | static inline bool unregister_chan( channel(T) & chan, select_node & node ) with(chan) {
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| 325 | // if ( !node`isListed && !node.park_counter ) return false; // handle special OR case C_TODO: try adding this back
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| 326 | lock( mutex_lock );
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| 327 | if ( node`isListed ) { // op wasn't performed
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| 328 | #ifdef CHAN_STATS
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| 329 | operations--;
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| 330 | #endif
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| 331 | remove( node );
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| 332 | unlock( mutex_lock );
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| 333 | return false;
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| 334 | }
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| 335 | unlock( mutex_lock );
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| 336 |
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| 337 | // only return true when not special OR case, not exceptional calse and status is SAT
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| 338 | return ( node.extra == 0p || !node.park_counter ) ? false : *node.clause_status == __SELECT_SAT;
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| 339 | }
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| 340 |
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| 341 | // type used by select statement to capture a chan read as the selected operation
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| 342 | struct chan_read {
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| 343 | T & ret;
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| 344 | channel(T) & chan;
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| 345 | };
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| 346 |
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| 347 | static inline void ?{}( chan_read(T) & cr, channel(T) & chan, T & ret ) {
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| 348 | &cr.chan = &chan;
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| 349 | &cr.ret = &ret;
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| 350 | }
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| 351 | static inline chan_read(T) ?<<?( T & ret, channel(T) & chan ) { chan_read(T) cr{ chan, ret }; return cr; }
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| 352 |
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| 353 | static inline void __handle_select_closed_read( chan_read(T) & this, select_node & node ) with(this.chan, this) {
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| 354 | __closed_remove( chan, ret );
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| 355 | // if we get here then the insert succeeded
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| 356 | __make_select_node_available( node );
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| 357 | }
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| 358 |
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| 359 | static inline bool register_select( chan_read(T) & this, select_node & node ) with(this.chan, this) {
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| 360 | lock( mutex_lock );
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| 361 | node.extra = &ret; // set .extra so that if it == 0p later in on_selected it is due to channel close
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| 362 |
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| 363 | #ifdef CHAN_STATS
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| 364 | if ( !closed ) operations++;
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| 365 | #endif
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| 366 |
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| 367 | if ( !node.park_counter ) {
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| 368 | // are we special case OR and front of cons is also special case OR
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| 369 | if ( !unlikely(closed) && !prods`isEmpty && prods`first.clause_status && !prods`first.park_counter ) {
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| 370 | if ( !__make_select_node_pending( node ) ) {
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| 371 | unlock( mutex_lock );
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| 372 | return false;
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| 373 | }
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| 374 |
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| 375 | if ( __handle_waituntil_OR( prods ) ) {
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| 376 | __prods_handoff( chan, ret );
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| 377 | __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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| 378 | unlock( mutex_lock );
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| 379 | return true;
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| 380 | }
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| 381 | __make_select_node_unsat( node );
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| 382 | }
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| 383 | // check if we can complete operation. If so race to establish winner in special OR case
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| 384 | if ( count != 0 || !prods`isEmpty || unlikely(closed) ) {
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| 385 | if ( !__make_select_node_available( node ) ) { // we didn't win the race so give up on registering
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| 386 | unlock( mutex_lock );
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| 387 | return false;
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| 388 | }
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| 389 | }
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| 390 | }
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| 391 |
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| 392 | if ( unlikely(closed) ) {
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| 393 | unlock( mutex_lock );
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| 394 | __handle_select_closed_read( this, node );
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| 395 | return true;
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| 396 | }
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| 397 |
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| 398 | // have to check for the zero size channel case
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| 399 | ZeroSize: if ( size == 0 && !prods`isEmpty ) {
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| 400 | if ( !__handle_waituntil_OR( prods ) ) break ZeroSize;
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| 401 | __prods_handoff( chan, ret );
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| 402 | __set_avail_then_unlock( node, mutex_lock );
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| 403 | return true;
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| 404 | }
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| 405 |
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| 406 | // wait if buffer is empty, work will be completed by someone else
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| 407 | if ( count == 0 ) {
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| 408 | #ifdef CHAN_STATS
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| 409 | blocks++;
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| 410 | #endif
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| 411 |
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| 412 | insert_last( cons, node );
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| 413 | unlock( mutex_lock );
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| 414 | return false;
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| 415 | }
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| 416 |
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| 417 | // Remove from buffer
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| 418 | __do_remove( chan, ret );
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| 419 | __set_avail_then_unlock( node, mutex_lock );
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| 420 | return true;
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| 421 | }
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| 422 | static inline bool unregister_select( chan_read(T) & this, select_node & node ) { return unregister_chan( this.chan, node ); }
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| 423 | static inline bool on_selected( chan_read(T) & this, select_node & node ) with(this) {
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| 424 | if ( node.extra == 0p ) // check if woken up due to closed channel
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| 425 | __closed_remove( chan, ret );
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| 426 | // This is only reachable if not closed or closed exception was handled
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| 427 | return true;
|
|---|
| 428 | }
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| 429 |
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| 430 | // type used by select statement to capture a chan write as the selected operation
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| 431 | struct chan_write {
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| 432 | T elem;
|
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| 433 | channel(T) & chan;
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| 434 | };
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| 435 |
|
|---|
| 436 | static inline void ?{}( chan_write(T) & cw, channel(T) & chan, T elem ) {
|
|---|
| 437 | &cw.chan = &chan;
|
|---|
| 438 | memcpy( (void *)&cw.elem, (void *)&elem, sizeof(T) );
|
|---|
| 439 | }
|
|---|
| 440 | static inline chan_write(T) ?>>?( T elem, channel(T) & chan ) { chan_write(T) cw{ chan, elem }; return cw; }
|
|---|
| 441 |
|
|---|
| 442 | static inline void __handle_select_closed_write( chan_write(T) & this, select_node & node ) with(this.chan, this) {
|
|---|
| 443 | __closed_insert( chan, elem );
|
|---|
| 444 | // if we get here then the insert succeeded
|
|---|
| 445 | __make_select_node_available( node );
|
|---|
| 446 | }
|
|---|
| 447 |
|
|---|
| 448 | static inline bool register_select( chan_write(T) & this, select_node & node ) with(this.chan, this) {
|
|---|
| 449 | lock( mutex_lock );
|
|---|
| 450 | node.extra = &elem; // set .extra so that if it == 0p later in on_selected it is due to channel close
|
|---|
| 451 |
|
|---|
| 452 | #ifdef CHAN_STATS
|
|---|
| 453 | if ( !closed ) operations++;
|
|---|
| 454 | #endif
|
|---|
| 455 |
|
|---|
| 456 | // special OR case handling
|
|---|
| 457 | if ( !node.park_counter ) {
|
|---|
| 458 | // are we special case OR and front of cons is also special case OR
|
|---|
| 459 | if ( !unlikely(closed) && !cons`isEmpty && cons`first.clause_status && !cons`first.park_counter ) {
|
|---|
| 460 | if ( !__make_select_node_pending( node ) ) {
|
|---|
| 461 | unlock( mutex_lock );
|
|---|
| 462 | return false;
|
|---|
| 463 | }
|
|---|
| 464 |
|
|---|
| 465 | if ( __handle_waituntil_OR( cons ) ) {
|
|---|
| 466 | __cons_handoff( chan, elem );
|
|---|
| 467 | __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
|
|---|
| 468 | unlock( mutex_lock );
|
|---|
| 469 | return true;
|
|---|
| 470 | }
|
|---|
| 471 | __make_select_node_unsat( node );
|
|---|
| 472 | }
|
|---|
| 473 | // check if we can complete operation. If so race to establish winner in special OR case
|
|---|
| 474 | if ( count != size || !cons`isEmpty || unlikely(closed) ) {
|
|---|
| 475 | if ( !__make_select_node_available( node ) ) { // we didn't win the race so give up on registering
|
|---|
| 476 | unlock( mutex_lock );
|
|---|
| 477 | return false;
|
|---|
| 478 | }
|
|---|
| 479 | }
|
|---|
| 480 | }
|
|---|
| 481 |
|
|---|
| 482 | // if closed handle
|
|---|
| 483 | if ( unlikely(closed) ) {
|
|---|
| 484 | unlock( mutex_lock );
|
|---|
| 485 | __handle_select_closed_write( this, node );
|
|---|
| 486 | return true;
|
|---|
| 487 | }
|
|---|
| 488 |
|
|---|
| 489 | // handle blocked consumer case via handoff (buffer is implicitly empty)
|
|---|
| 490 | ConsEmpty: if ( !cons`isEmpty ) {
|
|---|
| 491 | if ( !__handle_waituntil_OR( cons ) ) break ConsEmpty;
|
|---|
| 492 | __cons_handoff( chan, elem );
|
|---|
| 493 | __set_avail_then_unlock( node, mutex_lock );
|
|---|
| 494 | return true;
|
|---|
| 495 | }
|
|---|
| 496 |
|
|---|
| 497 | // insert node in list if buffer is full, work will be completed by someone else
|
|---|
| 498 | if ( count == size ) {
|
|---|
| 499 | #ifdef CHAN_STATS
|
|---|
| 500 | blocks++;
|
|---|
| 501 | #endif
|
|---|
| 502 |
|
|---|
| 503 | insert_last( prods, node );
|
|---|
| 504 | unlock( mutex_lock );
|
|---|
| 505 | return false;
|
|---|
| 506 | } // if
|
|---|
| 507 |
|
|---|
| 508 | // otherwise carry out write either via normal insert
|
|---|
| 509 | __buf_insert( chan, elem );
|
|---|
| 510 | __set_avail_then_unlock( node, mutex_lock );
|
|---|
| 511 | return true;
|
|---|
| 512 | }
|
|---|
| 513 | static inline bool unregister_select( chan_write(T) & this, select_node & node ) { return unregister_chan( this.chan, node ); }
|
|---|
| 514 |
|
|---|
| 515 | static inline bool on_selected( chan_write(T) & this, select_node & node ) with(this) {
|
|---|
| 516 | if ( node.extra == 0p ) // check if woken up due to closed channel
|
|---|
| 517 | __closed_insert( chan, elem );
|
|---|
| 518 |
|
|---|
| 519 | // This is only reachable if not closed or closed exception was handled
|
|---|
| 520 | return true;
|
|---|
| 521 | }
|
|---|
| 522 |
|
|---|
| 523 | } // forall( T )
|
|---|
| 524 |
|
|---|
| 525 |
|
|---|
