1 | // -*- Mode: CFA -*- |
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2 | // |
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3 | // Cforall Version 1.0.0 Copyright (C) 2016 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 | // monitor_desc.c -- |
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9 | // |
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10 | // Author : Thierry Delisle |
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11 | // Created On : Thd Feb 23 12:27:26 2017 |
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12 | // Last Modified By : Thierry Delisle |
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13 | // Last Modified On : -- |
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14 | // Update Count : 0 |
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15 | // |
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16 | |
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17 | #include "monitor" |
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18 | |
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19 | #include "kernel_private.h" |
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20 | |
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21 | void set_owner( monitor_desc * this, thread_desc * owner ) { |
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22 | //Pass the monitor appropriately |
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23 | this->owner = owner; |
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24 | |
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25 | //We are passing the monitor to someone else, which means recursion level is not 0 |
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26 | this->recursion = owner ? 1 : 0; |
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27 | } |
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28 | |
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29 | extern "C" { |
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30 | void __enter_monitor_desc(monitor_desc * this) { |
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31 | lock( &this->lock ); |
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32 | thread_desc * thrd = this_thread(); |
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33 | |
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34 | if( !this->owner ) { |
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35 | //No one has the monitor, just take it |
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36 | this->owner = thrd; |
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37 | this->recursion = 1; |
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38 | } |
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39 | else if( this->owner == thrd) { |
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40 | //We already have the monitor, just not how many times we took it |
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41 | assert( this->recursion > 0 ); |
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42 | this->recursion += 1; |
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43 | } |
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44 | else { |
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45 | //Some one else has the monitor, wait in line for it |
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46 | append( &this->entry_queue, thrd ); |
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47 | ScheduleInternal( &this->lock ); |
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48 | |
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49 | //ScheduleInternal will unlock spinlock, no need to unlock ourselves |
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50 | return; |
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51 | } |
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52 | |
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53 | unlock( &this->lock ); |
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54 | } |
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55 | |
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56 | // leave pseudo code : |
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57 | // decrement level |
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58 | // leve == 0 ? |
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59 | // no : done |
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60 | // yes : |
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61 | // signal stack empty ? |
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62 | // has leader : |
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63 | // bulk acquiring means we don't own the signal stack |
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64 | // ignore it but don't release the monitor |
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65 | // yes : |
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66 | // next in entry queue is new owner |
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67 | // no : |
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68 | // top of the signal stack is the owner |
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69 | // context switch to him right away |
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70 | // |
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71 | void __leave_monitor_desc(monitor_desc * this) { |
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72 | lock( &this->lock ); |
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73 | |
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74 | thread_desc * thrd = this_thread(); |
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75 | assert( thrd == this->owner ); |
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76 | |
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77 | //Leaving a recursion level, decrement the counter |
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78 | this->recursion -= 1; |
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79 | |
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80 | //If we haven't left the last level of recursion |
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81 | //it means we don't need to do anything |
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82 | if( this->recursion != 0) { |
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83 | unlock( &this->lock ); |
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84 | return; |
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85 | } |
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86 | |
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87 | //If we don't own the signal stack then just leave it to the owner |
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88 | if( this->stack_owner ) { |
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89 | assert( this->owner == this->stack_owner ); |
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90 | unlock( &this->lock ); |
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91 | return; |
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92 | } |
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93 | |
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94 | //We are the stack owner and have left the last recursion level. |
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95 | //We are in charge of passing the monitor |
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96 | thread_desc * new_owner = 0; |
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97 | |
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98 | //Check the signaller stack |
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99 | new_owner = pop( &this->signal_stack ); |
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100 | if( new_owner ) { |
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101 | //The signaller stack is not empty, |
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102 | //transfer control immediately |
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103 | set_owner( this, new_owner ); |
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104 | ScheduleInternal( &this->lock, new_owner ); |
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105 | return; |
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106 | } |
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107 | |
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108 | // No signaller thread |
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109 | // Get the next thread in the entry_queue |
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110 | new_owner = pop_head( &this->entry_queue ); |
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111 | set_owner( this, new_owner ); |
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112 | |
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113 | //We can now let other threads in safely |
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114 | unlock( &this->lock ); |
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115 | |
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116 | //We need to wake-up the thread |
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117 | ScheduleThread( new_owner ); |
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118 | } |
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119 | } |
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120 | |
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121 | void enter(monitor_desc ** monitors, int count) { |
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122 | for(int i = 0; i < count; i++) { |
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123 | __enter_monitor_desc( monitors[i] ); |
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124 | } |
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125 | } |
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126 | |
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127 | void leave(monitor_desc ** monitors, int count) { |
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128 | for(int i = count - 1; i >= 0; i--) { |
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129 | __leave_monitor_desc( monitors[i] ); |
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130 | } |
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131 | } |
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