| 1 | //
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| 2 | // Cforall Version 1.0.0 Copyright (C) 2016 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 | // bits/locks.hfa -- Basic spinlocks that are reused in the system.
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| 8 | // Used for locks that aren't specific to cforall threads and can be used anywhere
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| 9 | //
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| 10 | // *** Must not contain code specific to libcfathread ***
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| 11 | //
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| 12 | // Author : Thierry Delisle
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| 13 | // Created On : Tue Oct 31 15:14:38 2017
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| 14 | // Last Modified By : Peter A. Buhr
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| 15 | // Last Modified On : Wed Aug 12 14:18:07 2020
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| 16 | // Update Count : 13
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| 17 | //
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| 18 |
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| 19 | #pragma once
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| 20 |
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| 21 | #include "bits/debug.hfa"
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| 22 | #include "bits/defs.hfa"
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| 23 | #include <assert.h>
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| 24 |
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| 25 | struct __spinlock_t {
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| 26 | // Wrap in struct to prevent false sharing with debug info
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| 27 | volatile bool lock;
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| 28 | };
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| 29 |
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| 30 | #ifdef __cforall
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| 31 | extern "C" {
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| 32 | extern void disable_interrupts() OPTIONAL_THREAD;
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| 33 | extern void enable_interrupts( bool poll = true ) OPTIONAL_THREAD;
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| 34 | #define __cfaabi_dbg_record_lock(x, y)
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| 35 | }
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| 36 |
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| 37 | static inline void ?{}( __spinlock_t & this ) {
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| 38 | this.lock = 0;
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| 39 | }
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| 40 |
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| 41 | // Lock the spinlock, return false if already acquired
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| 42 | static inline bool try_lock ( __spinlock_t & this __cfaabi_dbg_ctx_param2 ) {
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| 43 | disable_interrupts();
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| 44 | bool result = (this.lock == 0) && (__atomic_test_and_set( &this.lock, __ATOMIC_ACQUIRE ) == 0);
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| 45 | if( result ) {
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| 46 | __cfaabi_dbg_record_lock( this, caller );
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| 47 | } else {
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| 48 | enable_interrupts( false );
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| 49 | }
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| 50 | return result;
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| 51 | }
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| 52 |
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| 53 | // Lock the spinlock, spin if already acquired
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| 54 | static inline void lock( __spinlock_t & this __cfaabi_dbg_ctx_param2 ) {
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| 55 | #ifndef NOEXPBACK
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| 56 | enum { SPIN_START = 4, SPIN_END = 64 * 1024, };
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| 57 | unsigned int spin = SPIN_START;
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| 58 | #endif
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| 59 |
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| 60 | disable_interrupts();
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| 61 | for ( unsigned int i = 1;; i += 1 ) {
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| 62 | if ( (this.lock == 0) && (__atomic_test_and_set( &this.lock, __ATOMIC_ACQUIRE ) == 0) ) break;
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| 63 | #ifndef NOEXPBACK
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| 64 | // exponential spin
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| 65 | for ( volatile unsigned int s = 0; s < spin; s += 1 ) Pause();
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| 66 |
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| 67 | // slowly increase by powers of 2
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| 68 | if ( i % 64 == 0 ) spin += spin;
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| 69 |
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| 70 | // prevent overflow
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| 71 | if ( spin > SPIN_END ) spin = SPIN_START;
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| 72 | #else
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| 73 | Pause();
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| 74 | #endif
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| 75 | }
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| 76 | __cfaabi_dbg_record_lock( this, caller );
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| 77 | }
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| 78 |
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| 79 | static inline void unlock( __spinlock_t & this ) {
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| 80 | __atomic_clear( &this.lock, __ATOMIC_RELEASE );
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| 81 | enable_interrupts( false );
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| 82 | }
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| 83 | #endif
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