[ea7d2b0] | 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.h -- Fast internal locks. |
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| 8 | // |
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| 9 | // Author : Thierry Delisle |
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| 10 | // Created On : Tue Oct 31 15:14:38 2017 |
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[b158d8f] | 11 | // Last Modified By : Peter A. Buhr |
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[b10affd] | 12 | // Last Modified On : Fri Mar 30 18:18:13 2018 |
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| 13 | // Update Count : 9 |
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[ea7d2b0] | 14 | // |
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| 15 | |
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| 16 | #pragma once |
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| 17 | |
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[875a72f] | 18 | #include "bits/debug.h" |
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[ea7d2b0] | 19 | #include "bits/defs.h" |
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| 20 | |
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| 21 | // pause to prevent excess processor bus usage |
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| 22 | #if defined( __sparc ) |
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| 23 | #define Pause() __asm__ __volatile__ ( "rd %ccr,%g0" ) |
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| 24 | #elif defined( __i386 ) || defined( __x86_64 ) |
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| 25 | #define Pause() __asm__ __volatile__ ( "pause" : : : ) |
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[b158d8f] | 26 | #elif defined( __ARM_ARCH ) |
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| 27 | #define Pause() __asm__ __volatile__ ( "nop" : : : ) |
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[ea7d2b0] | 28 | #else |
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| 29 | #error unsupported architecture |
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| 30 | #endif |
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| 31 | |
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[b158d8f] | 32 | #if defined( __i386 ) || defined( __x86_64 ) || defined( __ARM_ARCH ) |
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[ea7d2b0] | 33 | // Intel recommendation |
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| 34 | #define __ALIGN__ __attribute__(( aligned (128) )) |
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| 35 | #elif defined( __sparc ) |
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| 36 | #define __ALIGN__ CALIGN |
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| 37 | #else |
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| 38 | #error unsupported architecture |
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| 39 | #endif |
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| 40 | |
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| 41 | struct __spinlock_t { |
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[13073be] | 42 | // Wrap in struct to prevent false sharing with debug info |
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| 43 | struct { |
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| 44 | // Align lock on 128-bit boundary |
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| 45 | __ALIGN__ volatile _Bool lock; |
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| 46 | }; |
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[ea7d2b0] | 47 | #ifdef __CFA_DEBUG__ |
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[13073be] | 48 | // previous function to acquire the lock |
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[ea7d2b0] | 49 | const char * prev_name; |
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[13073be] | 50 | // previous thread to acquire the lock |
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[ea7d2b0] | 51 | void* prev_thrd; |
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| 52 | #endif |
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| 53 | } __ALIGN__; |
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| 54 | |
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[0cf5b79] | 55 | #ifdef __cforall |
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[dbe9b08] | 56 | extern "C" { |
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| 57 | extern void disable_interrupts(); |
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| 58 | extern void enable_interrupts_noPoll(); |
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| 59 | } |
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| 60 | |
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[ea7d2b0] | 61 | extern void yield( unsigned int ); |
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| 62 | |
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| 63 | static inline void ?{}( __spinlock_t & this ) { |
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| 64 | this.lock = 0; |
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| 65 | } |
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| 66 | |
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[9181f1d] | 67 | |
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| 68 | #ifdef __CFA_DEBUG__ |
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| 69 | void __cfaabi_dbg_record(__spinlock_t & this, const char * prev_name); |
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| 70 | #else |
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| 71 | #define __cfaabi_dbg_record(x, y) |
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| 72 | #endif |
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| 73 | |
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[ea7d2b0] | 74 | // Lock the spinlock, return false if already acquired |
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[36982fc] | 75 | static inline _Bool try_lock ( __spinlock_t & this __cfaabi_dbg_ctx_param2 ) { |
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[13073be] | 76 | _Bool result = (this.lock == 0) && (__atomic_test_and_set( &this.lock, __ATOMIC_ACQUIRE ) == 0); |
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[dbe9b08] | 77 | if( result ) { |
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| 78 | disable_interrupts(); |
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[9181f1d] | 79 | __cfaabi_dbg_record( this, caller ); |
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[dbe9b08] | 80 | } |
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[ea7d2b0] | 81 | return result; |
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| 82 | } |
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| 83 | |
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| 84 | // Lock the spinlock, spin if already acquired |
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[36982fc] | 85 | static inline void lock( __spinlock_t & this __cfaabi_dbg_ctx_param2 ) { |
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[ea7d2b0] | 86 | #ifndef NOEXPBACK |
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| 87 | enum { SPIN_START = 4, SPIN_END = 64 * 1024, }; |
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| 88 | unsigned int spin = SPIN_START; |
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| 89 | #endif |
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| 90 | |
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| 91 | for ( unsigned int i = 1;; i += 1 ) { |
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[13073be] | 92 | if ( (this.lock == 0) && (__atomic_test_and_set( &this.lock, __ATOMIC_ACQUIRE ) == 0) ) break; |
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[ea7d2b0] | 93 | #ifndef NOEXPBACK |
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| 94 | // exponential spin |
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| 95 | for ( volatile unsigned int s = 0; s < spin; s += 1 ) Pause(); |
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| 96 | |
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| 97 | // slowly increase by powers of 2 |
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| 98 | if ( i % 64 == 0 ) spin += spin; |
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| 99 | |
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| 100 | // prevent overflow |
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| 101 | if ( spin > SPIN_END ) spin = SPIN_START; |
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| 102 | #else |
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| 103 | Pause(); |
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| 104 | #endif |
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| 105 | } |
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[dbe9b08] | 106 | disable_interrupts(); |
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[9181f1d] | 107 | __cfaabi_dbg_record( this, caller ); |
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[ea7d2b0] | 108 | } |
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| 109 | |
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| 110 | static inline void unlock( __spinlock_t & this ) { |
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[dbe9b08] | 111 | enable_interrupts_noPoll(); |
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[13073be] | 112 | __atomic_clear( &this.lock, __ATOMIC_RELEASE ); |
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[ea7d2b0] | 113 | } |
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[b158d8f] | 114 | #endif |
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