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 -- 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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11 | // Last Modified By : Peter A. Buhr |
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12 | // Last Modified On : Wed Aug 12 14:18:07 2020 |
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13 | // Update Count : 13 |
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14 | // |
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15 | |
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16 | #pragma once |
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17 | |
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18 | #include "bits/debug.hfa" |
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19 | #include "bits/defs.hfa" |
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20 | #include <assert.h> |
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21 | |
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22 | #ifdef __cforall |
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23 | extern "C" { |
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24 | #include <pthread.h> |
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25 | } |
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26 | #endif |
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27 | |
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28 | // pause to prevent excess processor bus usage |
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29 | #if defined( __i386 ) || defined( __x86_64 ) |
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30 | #define Pause() __asm__ __volatile__ ( "pause" : : : ) |
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31 | #elif defined( __ARM_ARCH ) |
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32 | #define Pause() __asm__ __volatile__ ( "YIELD" : : : ) |
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33 | #else |
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34 | #error unsupported architecture |
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35 | #endif |
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36 | |
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37 | struct __spinlock_t { |
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38 | // Wrap in struct to prevent false sharing with debug info |
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39 | volatile bool lock; |
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40 | #ifdef __CFA_DEBUG__ |
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41 | // previous function to acquire the lock |
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42 | const char * prev_name; |
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43 | // previous thread to acquire the lock |
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44 | void* prev_thrd; |
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45 | #endif |
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46 | }; |
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47 | |
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48 | #ifdef __cforall |
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49 | extern "C" { |
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50 | extern void disable_interrupts() OPTIONAL_THREAD; |
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51 | extern void enable_interrupts_noPoll() OPTIONAL_THREAD; |
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52 | |
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53 | #ifdef __CFA_DEBUG__ |
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54 | void __cfaabi_dbg_record_lock(__spinlock_t & this, const char prev_name[]); |
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55 | #else |
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56 | #define __cfaabi_dbg_record_lock(x, y) |
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57 | #endif |
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58 | } |
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59 | |
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60 | static inline void ?{}( __spinlock_t & this ) { |
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61 | this.lock = 0; |
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62 | } |
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63 | |
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64 | // Lock the spinlock, return false if already acquired |
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65 | static inline bool try_lock ( __spinlock_t & this __cfaabi_dbg_ctx_param2 ) { |
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66 | disable_interrupts(); |
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67 | bool result = (this.lock == 0) && (__atomic_test_and_set( &this.lock, __ATOMIC_ACQUIRE ) == 0); |
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68 | if( result ) { |
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69 | __cfaabi_dbg_record_lock( this, caller ); |
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70 | } else { |
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71 | enable_interrupts_noPoll(); |
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72 | } |
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73 | return result; |
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74 | } |
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75 | |
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76 | // Lock the spinlock, spin if already acquired |
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77 | static inline void lock( __spinlock_t & this __cfaabi_dbg_ctx_param2 ) { |
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78 | #ifndef NOEXPBACK |
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79 | enum { SPIN_START = 4, SPIN_END = 64 * 1024, }; |
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80 | unsigned int spin = SPIN_START; |
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81 | #endif |
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82 | |
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83 | disable_interrupts(); |
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84 | for ( unsigned int i = 1;; i += 1 ) { |
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85 | if ( (this.lock == 0) && (__atomic_test_and_set( &this.lock, __ATOMIC_ACQUIRE ) == 0) ) break; |
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86 | #ifndef NOEXPBACK |
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87 | // exponential spin |
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88 | for ( volatile unsigned int s = 0; s < spin; s += 1 ) Pause(); |
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89 | |
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90 | // slowly increase by powers of 2 |
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91 | if ( i % 64 == 0 ) spin += spin; |
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92 | |
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93 | // prevent overflow |
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94 | if ( spin > SPIN_END ) spin = SPIN_START; |
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95 | #else |
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96 | Pause(); |
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97 | #endif |
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98 | } |
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99 | __cfaabi_dbg_record_lock( this, caller ); |
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100 | } |
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101 | |
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102 | static inline void unlock( __spinlock_t & this ) { |
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103 | __atomic_clear( &this.lock, __ATOMIC_RELEASE ); |
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104 | enable_interrupts_noPoll(); |
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105 | } |
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106 | |
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107 | |
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108 | #ifdef __CFA_WITH_VERIFY__ |
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109 | extern bool __cfaabi_dbg_in_kernel(); |
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110 | #endif |
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111 | |
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112 | extern "C" { |
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113 | char * strerror(int); |
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114 | } |
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115 | #define CHECKED(x) { int err = x; if( err != 0 ) abort("KERNEL ERROR: Operation \"" #x "\" return error %d - %s\n", err, strerror(err)); } |
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116 | |
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117 | struct __bin_sem_t { |
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118 | pthread_mutex_t lock; |
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119 | pthread_cond_t cond; |
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120 | int val; |
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121 | }; |
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122 | |
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123 | static inline void ?{}(__bin_sem_t & this) with( this ) { |
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124 | // Create the mutex with error checking |
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125 | pthread_mutexattr_t mattr; |
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126 | pthread_mutexattr_init( &mattr ); |
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127 | pthread_mutexattr_settype( &mattr, PTHREAD_MUTEX_ERRORCHECK_NP); |
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128 | pthread_mutex_init(&lock, &mattr); |
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129 | |
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130 | pthread_cond_init (&cond, (const pthread_condattr_t *)0p); // workaround trac#208: cast should not be required |
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131 | val = 0; |
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132 | } |
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133 | |
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134 | static inline void ^?{}(__bin_sem_t & this) with( this ) { |
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135 | CHECKED( pthread_mutex_destroy(&lock) ); |
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136 | CHECKED( pthread_cond_destroy (&cond) ); |
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137 | } |
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138 | |
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139 | static inline void wait(__bin_sem_t & this) with( this ) { |
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140 | verify(__cfaabi_dbg_in_kernel()); |
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141 | CHECKED( pthread_mutex_lock(&lock) ); |
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142 | while(val < 1) { |
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143 | pthread_cond_wait(&cond, &lock); |
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144 | } |
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145 | val -= 1; |
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146 | CHECKED( pthread_mutex_unlock(&lock) ); |
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147 | } |
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148 | |
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149 | static inline bool post(__bin_sem_t & this) with( this ) { |
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150 | bool needs_signal = false; |
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151 | |
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152 | CHECKED( pthread_mutex_lock(&lock) ); |
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153 | if(val < 1) { |
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154 | val += 1; |
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155 | pthread_cond_signal(&cond); |
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156 | needs_signal = true; |
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157 | } |
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158 | CHECKED( pthread_mutex_unlock(&lock) ); |
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159 | |
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160 | return needs_signal; |
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161 | } |
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162 | |
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163 | #undef CHECKED |
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164 | |
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165 | struct $thread; |
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166 | extern void park( void ); |
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167 | extern void unpark( struct $thread * this ); |
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168 | static inline struct $thread * active_thread (); |
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169 | |
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170 | // Semaphore which only supports a single thread |
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171 | struct single_sem { |
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172 | struct $thread * volatile ptr; |
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173 | }; |
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174 | |
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175 | static inline { |
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176 | void ?{}(single_sem & this) { |
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177 | this.ptr = 0p; |
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178 | } |
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179 | |
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180 | void ^?{}(single_sem &) {} |
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181 | |
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182 | bool wait(single_sem & this) { |
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183 | for() { |
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184 | struct $thread * expected = this.ptr; |
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185 | if(expected == 1p) { |
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186 | if(__atomic_compare_exchange_n(&this.ptr, &expected, 0p, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) { |
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187 | return false; |
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188 | } |
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189 | } |
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190 | else { |
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191 | /* paranoid */ verify( expected == 0p ); |
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192 | if(__atomic_compare_exchange_n(&this.ptr, &expected, active_thread(), false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) { |
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193 | park(); |
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194 | return true; |
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195 | } |
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196 | } |
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197 | |
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198 | } |
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199 | } |
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200 | |
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201 | bool post(single_sem & this) { |
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202 | for() { |
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203 | struct $thread * expected = this.ptr; |
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204 | if(expected == 1p) return false; |
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205 | if(expected == 0p) { |
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206 | if(__atomic_compare_exchange_n(&this.ptr, &expected, 1p, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) { |
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207 | return false; |
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208 | } |
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209 | } |
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210 | else { |
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211 | if(__atomic_compare_exchange_n(&this.ptr, &expected, 0p, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) { |
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212 | unpark( expected ); |
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213 | return true; |
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214 | } |
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215 | } |
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216 | } |
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217 | } |
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218 | } |
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219 | |
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220 | // Synchronozation primitive which only supports a single thread and one post |
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221 | // Similar to a binary semaphore with a 'one shot' semantic |
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222 | // is expected to be discarded after each party call their side |
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223 | struct oneshot { |
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224 | // Internal state : |
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225 | // 0p : is initial state (wait will block) |
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226 | // 1p : fulfilled (wait won't block) |
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227 | // any thread : a thread is currently waiting |
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228 | struct $thread * volatile ptr; |
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229 | }; |
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230 | |
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231 | static inline { |
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232 | void ?{}(oneshot & this) { |
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233 | this.ptr = 0p; |
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234 | } |
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235 | |
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236 | void ^?{}(oneshot &) {} |
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237 | |
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238 | // Wait for the post, return immidiately if it already happened. |
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239 | // return true if the thread was parked |
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240 | bool wait(oneshot & this) { |
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241 | for() { |
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242 | struct $thread * expected = this.ptr; |
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243 | if(expected == 1p) return false; |
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244 | /* paranoid */ verify( expected == 0p ); |
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245 | if(__atomic_compare_exchange_n(&this.ptr, &expected, active_thread(), false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) { |
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246 | park(); |
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247 | /* paranoid */ verify( this.ptr == 1p ); |
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248 | return true; |
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249 | } |
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250 | } |
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251 | } |
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252 | |
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253 | // Mark as fulfilled, wake thread if needed |
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254 | // return true if a thread was unparked |
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255 | bool post(oneshot & this) { |
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256 | struct $thread * got = __atomic_exchange_n( &this.ptr, 1p, __ATOMIC_SEQ_CST); |
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257 | if( got == 0p ) return false; |
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258 | unpark( got ); |
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259 | return true; |
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260 | } |
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261 | } |
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262 | |
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263 | // base types for future to build upon |
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264 | // It is based on the 'oneshot' type to allow multiple futures |
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265 | // to block on the same instance, permitting users to block a single |
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266 | // thread on "any of" [a given set of] futures. |
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267 | // does not support multiple threads waiting on the same future |
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268 | struct future_t { |
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269 | // Internal state : |
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270 | // 0p : is initial state (wait will block) |
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271 | // 1p : fulfilled (wait won't block) |
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272 | // 2p : in progress () |
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273 | // 3p : abandoned, server should delete |
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274 | // any oneshot : a context has been setup to wait, a thread could wait on it |
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275 | struct oneshot * volatile ptr; |
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276 | }; |
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277 | |
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278 | static inline { |
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279 | void ?{}(future_t & this) { |
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280 | this.ptr = 0p; |
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281 | } |
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282 | |
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283 | void ^?{}(future_t &) {} |
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284 | |
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285 | void reset(future_t & this) { |
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286 | // needs to be in 0p or 1p |
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287 | __atomic_exchange_n( &this.ptr, 0p, __ATOMIC_SEQ_CST); |
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288 | } |
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289 | |
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290 | // check if the future is available |
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291 | bool available( future_t & this ) { |
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292 | return this.ptr == 1p; |
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293 | } |
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294 | |
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295 | // Prepare the future to be waited on |
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296 | // intented to be use by wait, wait_any, waitfor, etc. rather than used directly |
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297 | bool setup( future_t & this, oneshot & wait_ctx ) { |
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298 | /* paranoid */ verify( wait_ctx.ptr == 0p ); |
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299 | // The future needs to set the wait context |
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300 | for() { |
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301 | struct oneshot * expected = this.ptr; |
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302 | // Is the future already fulfilled? |
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303 | if(expected == 1p) return false; // Yes, just return false (didn't block) |
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304 | |
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305 | // The future is not fulfilled, try to setup the wait context |
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306 | /* paranoid */ verify( expected == 0p ); |
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307 | if(__atomic_compare_exchange_n(&this.ptr, &expected, &wait_ctx, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) { |
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308 | return true; |
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309 | } |
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310 | } |
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311 | } |
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312 | |
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313 | // Stop waiting on a future |
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314 | // When multiple futures are waited for together in "any of" pattern |
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315 | // futures that weren't fulfilled before the thread woke up |
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316 | // should retract the wait ctx |
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317 | // intented to be use by wait, wait_any, waitfor, etc. rather than used directly |
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318 | void retract( future_t & this, oneshot & wait_ctx ) { |
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319 | // Remove the wait context |
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320 | struct oneshot * got = __atomic_exchange_n( &this.ptr, 0p, __ATOMIC_SEQ_CST); |
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321 | |
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322 | // got == 0p: future was never actually setup, just return |
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323 | if( got == 0p ) return; |
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324 | |
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325 | // got == wait_ctx: since fulfil does an atomic_swap, |
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326 | // if we got back the original then no one else saw context |
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327 | // It is safe to delete (which could happen after the return) |
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328 | if( got == &wait_ctx ) return; |
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329 | |
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330 | // got == 1p: the future is ready and the context was fully consumed |
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331 | // the server won't use the pointer again |
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332 | // It is safe to delete (which could happen after the return) |
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333 | if( got == 1p ) return; |
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334 | |
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335 | // got == 2p: the future is ready but the context hasn't fully been consumed |
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336 | // spin until it is safe to move on |
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337 | if( got == 2p ) { |
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338 | while( this.ptr != 1p ) Pause(); |
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339 | return; |
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340 | } |
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341 | |
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342 | // got == any thing else, something wen't wrong here, abort |
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343 | abort("Future in unexpected state"); |
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344 | } |
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345 | |
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346 | // Mark the future as abandoned, meaning it will be deleted by the server |
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347 | bool abandon( future_t & this ) { |
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348 | /* paranoid */ verify( this.ptr != 3p ); |
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349 | |
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350 | // Mark the future as abandonned |
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351 | struct oneshot * got = __atomic_exchange_n( &this.ptr, 3p, __ATOMIC_SEQ_CST); |
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352 | |
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353 | // If the future isn't already fulfilled, let the server delete it |
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354 | if( got == 0p ) return false; |
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355 | |
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356 | // got == 2p: the future is ready but the context hasn't fully been consumed |
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357 | // spin until it is safe to move on |
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358 | if( got == 2p ) { |
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359 | while( this.ptr != 1p ) Pause(); |
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360 | got = 1p; |
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361 | } |
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362 | |
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363 | // The future is completed delete it now |
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364 | /* paranoid */ verify( this.ptr != 1p ); |
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365 | free( &this ); |
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366 | return true; |
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367 | } |
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368 | |
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369 | // from the server side, mark the future as fulfilled |
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370 | // delete it if needed |
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371 | bool fulfil( future_t & this ) { |
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372 | for() { |
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373 | struct oneshot * expected = this.ptr; |
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374 | // was this abandoned? |
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375 | #if defined(__GNUC__) && __GNUC__ >= 7 |
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376 | #pragma GCC diagnostic push |
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377 | #pragma GCC diagnostic ignored "-Wfree-nonheap-object" |
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378 | #endif |
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379 | if( expected == 3p ) { free( &this ); return false; } |
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380 | #if defined(__GNUC__) && __GNUC__ >= 7 |
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381 | #pragma GCC diagnostic pop |
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382 | #endif |
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383 | |
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384 | /* paranoid */ verify( expected != 1p ); // Future is already fulfilled, should not happen |
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385 | /* paranoid */ verify( expected != 2p ); // Future is bein fulfilled by someone else, this is even less supported then the previous case. |
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386 | |
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387 | // If there is a wait context, we need to consume it and mark it as consumed after |
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388 | // If there is no context then we can skip the in progress phase |
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389 | struct oneshot * want = expected == 0p ? 1p : 2p; |
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390 | if(__atomic_compare_exchange_n(&this.ptr, &expected, want, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) { |
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391 | if( expected == 0p ) { /* paranoid */ verify( this.ptr == 1p); return false; } |
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392 | bool ret = post( *expected ); |
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393 | __atomic_store_n( &this.ptr, 1p, __ATOMIC_SEQ_CST); |
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394 | return ret; |
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395 | } |
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396 | } |
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397 | |
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398 | } |
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399 | |
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400 | // Wait for the future to be fulfilled |
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401 | bool wait( future_t & this ) { |
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402 | oneshot temp; |
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403 | if( !setup(this, temp) ) return false; |
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404 | |
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405 | // Wait context is setup, just wait on it |
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406 | bool ret = wait( temp ); |
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407 | |
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408 | // Wait for the future to tru |
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409 | while( this.ptr == 2p ) Pause(); |
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410 | // Make sure the state makes sense |
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411 | // Should be fulfilled, could be in progress but it's out of date if so |
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412 | // since if that is the case, the oneshot was fulfilled (unparking this thread) |
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413 | // and the oneshot should not be needed any more |
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414 | __attribute__((unused)) struct oneshot * was = this.ptr; |
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415 | /* paranoid */ verifyf( was == 1p, "Expected this.ptr to be 1p, was %p\n", was ); |
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416 | |
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417 | // Mark the future as fulfilled, to be consistent |
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418 | // with potential calls to avail |
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419 | // this.ptr = 1p; |
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420 | return ret; |
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421 | } |
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422 | } |
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423 | #endif |
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