| 1 | // -*- Mode: C -*-
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| 2 | //
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| 3 | // Cforall Version 1.0.0 Copyright (C) 2022 University of Waterloo
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| 4 | //
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| 5 | // The contents of this file are covered under the licence agreement in the
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| 6 | // file "LICENCE" distributed with Cforall.
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| 7 | //
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| 8 | // barrier.hfa -- simple barrier implemented using a monitor
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| 9 | //
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| 10 | // Author : Peter A. Buhr
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| 11 | // Created On : Sun Nov 10 08:07:35 2024
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| 12 | // Last Modified By : Peter A. Buhr
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| 13 | // Last Modified On : Thu Oct 30 21:20:18 2025
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| 14 | // Update Count : 67
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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 <monitor.hfa>
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| 21 |
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| 22 | // Plan 9 inheritance does not work with monitors. Two monitor locks are created.
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| 23 |
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| 24 | typedef void (* barrier_fptr_t)( ... ); // like C++, () => void and ... => C ()
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| 25 |
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| 26 | monitor barrier {
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| 27 | unsigned int group$, arrivals$; // group size, arrival counter (backward)
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| 28 | condition c$; // wait for group to form
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| 29 | barrier_fptr_t callback$; // global callback
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| 30 | void * arg$; // global callback argument
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| 31 | };
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| 32 |
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| 33 | static inline void ?{}( barrier & b, unsigned int group, barrier_fptr_t callback, void * arg ) with ( b ) {
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| 34 | [group$, arrivals$] = group;
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| 35 | [callback$, arg$] = [callback, arg];
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| 36 | }
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| 37 |
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| 38 | static inline void ?{}( barrier & b, unsigned int group ) { (b){ group, 0p, 0p }; } // call base constructor
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| 39 | static inline unsigned int waiters( barrier & b ) with( b ) { return group$ - arrivals$; }
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| 40 | static inline unsigned int total( barrier & b ) with( b ) { return group$; }
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| 41 |
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| 42 | // Returns a value indicating the reverse order the threads arrived, i.e., the Gth thread returns 0 (and does not
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| 43 | // block). olock is an optional mutex lock held by the called and atomically released and block. callback is an
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| 44 | // optional function that is called by the Gth thread before unblocking the other threads. arg is an optional (void *)
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| 45 | // argument passed to the callback.
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| 46 |
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| 47 | // Barrier is a monitor => implicit mutual exclusion.
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| 48 | static inline unsigned int block( barrier & mutex b, owner_lock & olock, barrier_fptr_t callback, void * arg ) with( b ) {
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| 49 | arrivals$ -= 1; // prefix decrement so last is 0 not 1
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| 50 | typeof( arrivals$ ) arrived = arrivals$; // note arrival order
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| 51 | if ( arrivals$ != 0 ) { // wait for group to form
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| 52 | if ( &olock != 0p ) unlock( olock ); // if lock specified, release it
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| 53 | wait( c$ );
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| 54 | // DO NOT REACQUIRE LOCK TO ALLOW BARGING PREVENTION
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| 55 | } else { // group formed
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| 56 | if ( callback ) callback( arg ); // if callback specified, safe to call with argument
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| 57 | else if ( callback$ ) callback$( arg$ ); // if callback specified, safe to call with argument
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| 58 | signal_all( c$ ); // unblock group
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| 59 | arrivals$ = group$; // reset
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| 60 | } // if
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| 61 | return arrived; // return arrival order
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| 62 | }
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| 63 |
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| 64 | static inline unsigned int block( barrier & b ) { return block( b, *0p, 0p, 0p ); }
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| 65 | static inline unsigned int block( barrier & b, owner_lock & olock ) { return block( b, olock, 0p, 0p ); }
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| 66 | static inline unsigned int block( barrier & b, barrier_fptr_t callback ) { return block( b, *0p, callback, 0p ); }
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| 67 | static inline unsigned int block( barrier & b, barrier_fptr_t callback, void * arg ) { return block( b, *0p, callback, arg ); }
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| 68 | static inline unsigned int block( barrier & b, owner_lock & olock, barrier_fptr_t callback ) { return block( b, olock, callback, 0p ); }
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