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<div class="fragment"><div class="line"><a id="l00001" name="l00001"></a><span class="lineno"> 1</span><span class="comment">// This file is part of Eigen, a lightweight C++ template library</span></div>
<div class="line"><a id="l00002" name="l00002"></a><span class="lineno"> 2</span><span class="comment">// for linear algebra.</span></div>
<div class="line"><a id="l00003" name="l00003"></a><span class="lineno"> 3</span><span class="comment">//</span></div>
<div class="line"><a id="l00004" name="l00004"></a><span class="lineno"> 4</span><span class="comment">// Copyright (C) 2016 Dmitry Vyukov <[email protected]></span></div>
<div class="line"><a id="l00005" name="l00005"></a><span class="lineno"> 5</span><span class="comment">//</span></div>
<div class="line"><a id="l00006" name="l00006"></a><span class="lineno"> 6</span><span class="comment">// This Source Code Form is subject to the terms of the Mozilla</span></div>
<div class="line"><a id="l00007" name="l00007"></a><span class="lineno"> 7</span><span class="comment">// Public License v. 2.0. If a copy of the MPL was not distributed</span></div>
<div class="line"><a id="l00008" name="l00008"></a><span class="lineno"> 8</span><span class="comment">// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.</span></div>
<div class="line"><a id="l00009" name="l00009"></a><span class="lineno"> 9</span> </div>
<div class="line"><a id="l00010" name="l00010"></a><span class="lineno"> 10</span><span class="preprocessor">#ifndef EIGEN_CXX11_THREADPOOL_EVENTCOUNT_H</span></div>
<div class="line"><a id="l00011" name="l00011"></a><span class="lineno"> 11</span><span class="preprocessor">#define EIGEN_CXX11_THREADPOOL_EVENTCOUNT_H</span></div>
<div class="line"><a id="l00012" name="l00012"></a><span class="lineno"> 12</span> </div>
<div class="line"><a id="l00013" name="l00013"></a><span class="lineno"> 13</span><span class="preprocessor">#include "./InternalHeaderCheck.h"</span></div>
<div class="line"><a id="l00014" name="l00014"></a><span class="lineno"> 14</span> </div>
<div class="line"><a id="l00015" name="l00015"></a><span class="lineno"> 15</span><span class="keyword">namespace </span><a class="code hl_namespace" href="namespaceEigen.html">Eigen</a> {</div>
<div class="line"><a id="l00016" name="l00016"></a><span class="lineno"> 16</span> </div>
<div class="line"><a id="l00017" name="l00017"></a><span class="lineno"> 17</span><span class="comment">// EventCount allows to wait for arbitrary predicates in non-blocking</span></div>
<div class="line"><a id="l00018" name="l00018"></a><span class="lineno"> 18</span><span class="comment">// algorithms. Think of condition variable, but wait predicate does not need to</span></div>
<div class="line"><a id="l00019" name="l00019"></a><span class="lineno"> 19</span><span class="comment">// be protected by a mutex. Usage:</span></div>
<div class="line"><a id="l00020" name="l00020"></a><span class="lineno"> 20</span><span class="comment">// Waiting thread does:</span></div>
<div class="line"><a id="l00021" name="l00021"></a><span class="lineno"> 21</span><span class="comment">//</span></div>
<div class="line"><a id="l00022" name="l00022"></a><span class="lineno"> 22</span><span class="comment">// if (predicate)</span></div>
<div class="line"><a id="l00023" name="l00023"></a><span class="lineno"> 23</span><span class="comment">// return act();</span></div>
<div class="line"><a id="l00024" name="l00024"></a><span class="lineno"> 24</span><span class="comment">// EventCount::Waiter& w = waiters[my_index];</span></div>
<div class="line"><a id="l00025" name="l00025"></a><span class="lineno"> 25</span><span class="comment">// ec.Prewait(&w);</span></div>
<div class="line"><a id="l00026" name="l00026"></a><span class="lineno"> 26</span><span class="comment">// if (predicate) {</span></div>
<div class="line"><a id="l00027" name="l00027"></a><span class="lineno"> 27</span><span class="comment">// ec.CancelWait(&w);</span></div>
<div class="line"><a id="l00028" name="l00028"></a><span class="lineno"> 28</span><span class="comment">// return act();</span></div>
<div class="line"><a id="l00029" name="l00029"></a><span class="lineno"> 29</span><span class="comment">// }</span></div>
<div class="line"><a id="l00030" name="l00030"></a><span class="lineno"> 30</span><span class="comment">// ec.CommitWait(&w);</span></div>
<div class="line"><a id="l00031" name="l00031"></a><span class="lineno"> 31</span><span class="comment">//</span></div>
<div class="line"><a id="l00032" name="l00032"></a><span class="lineno"> 32</span><span class="comment">// Notifying thread does:</span></div>
<div class="line"><a id="l00033" name="l00033"></a><span class="lineno"> 33</span><span class="comment">//</span></div>
<div class="line"><a id="l00034" name="l00034"></a><span class="lineno"> 34</span><span class="comment">// predicate = true;</span></div>
<div class="line"><a id="l00035" name="l00035"></a><span class="lineno"> 35</span><span class="comment">// ec.Notify(true);</span></div>
<div class="line"><a id="l00036" name="l00036"></a><span class="lineno"> 36</span><span class="comment">//</span></div>
<div class="line"><a id="l00037" name="l00037"></a><span class="lineno"> 37</span><span class="comment">// Notify is cheap if there are no waiting threads. Prewait/CommitWait are not</span></div>
<div class="line"><a id="l00038" name="l00038"></a><span class="lineno"> 38</span><span class="comment">// cheap, but they are executed only if the preceding predicate check has</span></div>
<div class="line"><a id="l00039" name="l00039"></a><span class="lineno"> 39</span><span class="comment">// failed.</span></div>
<div class="line"><a id="l00040" name="l00040"></a><span class="lineno"> 40</span><span class="comment">//</span></div>
<div class="line"><a id="l00041" name="l00041"></a><span class="lineno"> 41</span><span class="comment">// Algorithm outline:</span></div>
<div class="line"><a id="l00042" name="l00042"></a><span class="lineno"> 42</span><span class="comment">// There are two main variables: predicate (managed by user) and state_.</span></div>
<div class="line"><a id="l00043" name="l00043"></a><span class="lineno"> 43</span><span class="comment">// Operation closely resembles Dekker mutual algorithm:</span></div>
<div class="line"><a id="l00044" name="l00044"></a><span class="lineno"> 44</span><span class="comment">// https://en.wikipedia.org/wiki/Dekker%27s_algorithm</span></div>
<div class="line"><a id="l00045" name="l00045"></a><span class="lineno"> 45</span><span class="comment">// Waiting thread sets state_ then checks predicate, Notifying thread sets</span></div>
<div class="line"><a id="l00046" name="l00046"></a><span class="lineno"> 46</span><span class="comment">// predicate then checks state_. Due to seq_cst fences in between these</span></div>
<div class="line"><a id="l00047" name="l00047"></a><span class="lineno"> 47</span><span class="comment">// operations it is guaranteed than either waiter will see predicate change</span></div>
<div class="line"><a id="l00048" name="l00048"></a><span class="lineno"> 48</span><span class="comment">// and won't block, or notifying thread will see state_ change and will unblock</span></div>
<div class="line"><a id="l00049" name="l00049"></a><span class="lineno"> 49</span><span class="comment">// the waiter, or both. But it can't happen that both threads don't see each</span></div>
<div class="line"><a id="l00050" name="l00050"></a><span class="lineno"> 50</span><span class="comment">// other changes, which would lead to deadlock.</span></div>
<div class="line"><a id="l00051" name="l00051"></a><span class="lineno"> 51</span><span class="keyword">class </span>EventCount {</div>
<div class="line"><a id="l00052" name="l00052"></a><span class="lineno"> 52</span> <span class="keyword">public</span>:</div>
<div class="line"><a id="l00053" name="l00053"></a><span class="lineno"> 53</span> <span class="keyword">class </span>Waiter;</div>
<div class="line"><a id="l00054" name="l00054"></a><span class="lineno"> 54</span> </div>
<div class="line"><a id="l00055" name="l00055"></a><span class="lineno"> 55</span> EventCount(MaxSizeVector<Waiter>& waiters)</div>
<div class="line"><a id="l00056" name="l00056"></a><span class="lineno"> 56</span> : state_(kStackMask), waiters_(waiters) {</div>
<div class="line"><a id="l00057" name="l00057"></a><span class="lineno"> 57</span> eigen_plain_assert(waiters.size() < (1 << kWaiterBits) - 1);</div>
<div class="line"><a id="l00058" name="l00058"></a><span class="lineno"> 58</span> }</div>
<div class="line"><a id="l00059" name="l00059"></a><span class="lineno"> 59</span> </div>
<div class="line"><a id="l00060" name="l00060"></a><span class="lineno"> 60</span> ~EventCount() {</div>
<div class="line"><a id="l00061" name="l00061"></a><span class="lineno"> 61</span> <span class="comment">// Ensure there are no waiters.</span></div>
<div class="line"><a id="l00062" name="l00062"></a><span class="lineno"> 62</span> eigen_plain_assert(state_.load() == kStackMask);</div>
<div class="line"><a id="l00063" name="l00063"></a><span class="lineno"> 63</span> }</div>
<div class="line"><a id="l00064" name="l00064"></a><span class="lineno"> 64</span> </div>
<div class="line"><a id="l00065" name="l00065"></a><span class="lineno"> 65</span> <span class="comment">// Prewait prepares for waiting.</span></div>
<div class="line"><a id="l00066" name="l00066"></a><span class="lineno"> 66</span> <span class="comment">// After calling Prewait, the thread must re-check the wait predicate</span></div>
<div class="line"><a id="l00067" name="l00067"></a><span class="lineno"> 67</span> <span class="comment">// and then call either CancelWait or CommitWait.</span></div>
<div class="line"><a id="l00068" name="l00068"></a><span class="lineno"> 68</span> <span class="keywordtype">void</span> Prewait() {</div>
<div class="line"><a id="l00069" name="l00069"></a><span class="lineno"> 69</span> uint64_t state = state_.load(std::memory_order_relaxed);</div>
<div class="line"><a id="l00070" name="l00070"></a><span class="lineno"> 70</span> <span class="keywordflow">for</span> (;;) {</div>
<div class="line"><a id="l00071" name="l00071"></a><span class="lineno"> 71</span> CheckState(state);</div>
<div class="line"><a id="l00072" name="l00072"></a><span class="lineno"> 72</span> uint64_t newstate = state + kWaiterInc;</div>
<div class="line"><a id="l00073" name="l00073"></a><span class="lineno"> 73</span> CheckState(newstate);</div>
<div class="line"><a id="l00074" name="l00074"></a><span class="lineno"> 74</span> <span class="keywordflow">if</span> (state_.compare_exchange_weak(state, newstate,</div>
<div class="line"><a id="l00075" name="l00075"></a><span class="lineno"> 75</span> std::memory_order_seq_cst))</div>
<div class="line"><a id="l00076" name="l00076"></a><span class="lineno"> 76</span> <span class="keywordflow">return</span>;</div>
<div class="line"><a id="l00077" name="l00077"></a><span class="lineno"> 77</span> }</div>
<div class="line"><a id="l00078" name="l00078"></a><span class="lineno"> 78</span> }</div>
<div class="line"><a id="l00079" name="l00079"></a><span class="lineno"> 79</span> </div>
<div class="line"><a id="l00080" name="l00080"></a><span class="lineno"> 80</span> <span class="comment">// CommitWait commits waiting after Prewait.</span></div>
<div class="line"><a id="l00081" name="l00081"></a><span class="lineno"> 81</span> <span class="keywordtype">void</span> CommitWait(Waiter* w) {</div>
<div class="line"><a id="l00082" name="l00082"></a><span class="lineno"> 82</span> eigen_plain_assert((w->epoch & ~kEpochMask) == 0);</div>
<div class="line"><a id="l00083" name="l00083"></a><span class="lineno"> 83</span> w->state = Waiter::kNotSignaled;</div>
<div class="line"><a id="l00084" name="l00084"></a><span class="lineno"> 84</span> <span class="keyword">const</span> uint64_t me = (w - &waiters_[0]) | w->epoch;</div>
<div class="line"><a id="l00085" name="l00085"></a><span class="lineno"> 85</span> uint64_t state = state_.load(std::memory_order_seq_cst);</div>
<div class="line"><a id="l00086" name="l00086"></a><span class="lineno"> 86</span> <span class="keywordflow">for</span> (;;) {</div>
<div class="line"><a id="l00087" name="l00087"></a><span class="lineno"> 87</span> CheckState(state, <span class="keyword">true</span>);</div>
<div class="line"><a id="l00088" name="l00088"></a><span class="lineno"> 88</span> uint64_t newstate;</div>
<div class="line"><a id="l00089" name="l00089"></a><span class="lineno"> 89</span> <span class="keywordflow">if</span> ((state & kSignalMask) != 0) {</div>
<div class="line"><a id="l00090" name="l00090"></a><span class="lineno"> 90</span> <span class="comment">// Consume the signal and return immediately.</span></div>
<div class="line"><a id="l00091" name="l00091"></a><span class="lineno"> 91</span> newstate = state - kWaiterInc - kSignalInc;</div>
<div class="line"><a id="l00092" name="l00092"></a><span class="lineno"> 92</span> } <span class="keywordflow">else</span> {</div>
<div class="line"><a id="l00093" name="l00093"></a><span class="lineno"> 93</span> <span class="comment">// Remove this thread from pre-wait counter and add to the waiter stack.</span></div>
<div class="line"><a id="l00094" name="l00094"></a><span class="lineno"> 94</span> newstate = ((state & kWaiterMask) - kWaiterInc) | me;</div>
<div class="line"><a id="l00095" name="l00095"></a><span class="lineno"> 95</span> w->next.store(state & (kStackMask | kEpochMask),</div>
<div class="line"><a id="l00096" name="l00096"></a><span class="lineno"> 96</span> std::memory_order_relaxed);</div>
<div class="line"><a id="l00097" name="l00097"></a><span class="lineno"> 97</span> }</div>
<div class="line"><a id="l00098" name="l00098"></a><span class="lineno"> 98</span> CheckState(newstate);</div>
<div class="line"><a id="l00099" name="l00099"></a><span class="lineno"> 99</span> <span class="keywordflow">if</span> (state_.compare_exchange_weak(state, newstate,</div>
<div class="line"><a id="l00100" name="l00100"></a><span class="lineno"> 100</span> std::memory_order_acq_rel)) {</div>
<div class="line"><a id="l00101" name="l00101"></a><span class="lineno"> 101</span> <span class="keywordflow">if</span> ((state & kSignalMask) == 0) {</div>
<div class="line"><a id="l00102" name="l00102"></a><span class="lineno"> 102</span> w->epoch += kEpochInc;</div>
<div class="line"><a id="l00103" name="l00103"></a><span class="lineno"> 103</span> Park(w);</div>
<div class="line"><a id="l00104" name="l00104"></a><span class="lineno"> 104</span> }</div>
<div class="line"><a id="l00105" name="l00105"></a><span class="lineno"> 105</span> <span class="keywordflow">return</span>;</div>
<div class="line"><a id="l00106" name="l00106"></a><span class="lineno"> 106</span> }</div>
<div class="line"><a id="l00107" name="l00107"></a><span class="lineno"> 107</span> }</div>
<div class="line"><a id="l00108" name="l00108"></a><span class="lineno"> 108</span> }</div>
<div class="line"><a id="l00109" name="l00109"></a><span class="lineno"> 109</span> </div>
<div class="line"><a id="l00110" name="l00110"></a><span class="lineno"> 110</span> <span class="comment">// CancelWait cancels effects of the previous Prewait call.</span></div>
<div class="line"><a id="l00111" name="l00111"></a><span class="lineno"> 111</span> <span class="keywordtype">void</span> CancelWait() {</div>
<div class="line"><a id="l00112" name="l00112"></a><span class="lineno"> 112</span> uint64_t state = state_.load(std::memory_order_relaxed);</div>
<div class="line"><a id="l00113" name="l00113"></a><span class="lineno"> 113</span> <span class="keywordflow">for</span> (;;) {</div>
<div class="line"><a id="l00114" name="l00114"></a><span class="lineno"> 114</span> CheckState(state, <span class="keyword">true</span>);</div>
<div class="line"><a id="l00115" name="l00115"></a><span class="lineno"> 115</span> uint64_t newstate = state - kWaiterInc;</div>
<div class="line"><a id="l00116" name="l00116"></a><span class="lineno"> 116</span> <span class="comment">// We don't know if the thread was also notified or not,</span></div>
<div class="line"><a id="l00117" name="l00117"></a><span class="lineno"> 117</span> <span class="comment">// so we should not consume a signal unconditionally.</span></div>
<div class="line"><a id="l00118" name="l00118"></a><span class="lineno"> 118</span> <span class="comment">// Only if number of waiters is equal to number of signals,</span></div>
<div class="line"><a id="l00119" name="l00119"></a><span class="lineno"> 119</span> <span class="comment">// we know that the thread was notified and we must take away the signal.</span></div>
<div class="line"><a id="l00120" name="l00120"></a><span class="lineno"> 120</span> <span class="keywordflow">if</span> (((state & kWaiterMask) >> kWaiterShift) ==</div>
<div class="line"><a id="l00121" name="l00121"></a><span class="lineno"> 121</span> ((state & kSignalMask) >> kSignalShift))</div>
<div class="line"><a id="l00122" name="l00122"></a><span class="lineno"> 122</span> newstate -= kSignalInc;</div>
<div class="line"><a id="l00123" name="l00123"></a><span class="lineno"> 123</span> CheckState(newstate);</div>
<div class="line"><a id="l00124" name="l00124"></a><span class="lineno"> 124</span> <span class="keywordflow">if</span> (state_.compare_exchange_weak(state, newstate,</div>
<div class="line"><a id="l00125" name="l00125"></a><span class="lineno"> 125</span> std::memory_order_acq_rel))</div>
<div class="line"><a id="l00126" name="l00126"></a><span class="lineno"> 126</span> <span class="keywordflow">return</span>;</div>
<div class="line"><a id="l00127" name="l00127"></a><span class="lineno"> 127</span> }</div>
<div class="line"><a id="l00128" name="l00128"></a><span class="lineno"> 128</span> }</div>
<div class="line"><a id="l00129" name="l00129"></a><span class="lineno"> 129</span> </div>
<div class="line"><a id="l00130" name="l00130"></a><span class="lineno"> 130</span> <span class="comment">// Notify wakes one or all waiting threads.</span></div>
<div class="line"><a id="l00131" name="l00131"></a><span class="lineno"> 131</span> <span class="comment">// Must be called after changing the associated wait predicate.</span></div>
<div class="line"><a id="l00132" name="l00132"></a><span class="lineno"> 132</span> <span class="keywordtype">void</span> Notify(<span class="keywordtype">bool</span> notifyAll) {</div>
<div class="line"><a id="l00133" name="l00133"></a><span class="lineno"> 133</span> std::atomic_thread_fence(std::memory_order_seq_cst);</div>
<div class="line"><a id="l00134" name="l00134"></a><span class="lineno"> 134</span> uint64_t state = state_.load(std::memory_order_acquire);</div>
<div class="line"><a id="l00135" name="l00135"></a><span class="lineno"> 135</span> <span class="keywordflow">for</span> (;;) {</div>
<div class="line"><a id="l00136" name="l00136"></a><span class="lineno"> 136</span> CheckState(state);</div>
<div class="line"><a id="l00137" name="l00137"></a><span class="lineno"> 137</span> <span class="keyword">const</span> uint64_t waiters = (state & kWaiterMask) >> kWaiterShift;</div>
<div class="line"><a id="l00138" name="l00138"></a><span class="lineno"> 138</span> <span class="keyword">const</span> uint64_t signals = (state & kSignalMask) >> kSignalShift;</div>
<div class="line"><a id="l00139" name="l00139"></a><span class="lineno"> 139</span> <span class="comment">// Easy case: no waiters.</span></div>
<div class="line"><a id="l00140" name="l00140"></a><span class="lineno"> 140</span> <span class="keywordflow">if</span> ((state & kStackMask) == kStackMask && waiters == signals) <span class="keywordflow">return</span>;</div>
<div class="line"><a id="l00141" name="l00141"></a><span class="lineno"> 141</span> uint64_t newstate;</div>
<div class="line"><a id="l00142" name="l00142"></a><span class="lineno"> 142</span> <span class="keywordflow">if</span> (notifyAll) {</div>
<div class="line"><a id="l00143" name="l00143"></a><span class="lineno"> 143</span> <span class="comment">// Empty wait stack and set signal to number of pre-wait threads.</span></div>
<div class="line"><a id="l00144" name="l00144"></a><span class="lineno"> 144</span> newstate =</div>
<div class="line"><a id="l00145" name="l00145"></a><span class="lineno"> 145</span> (state & kWaiterMask) | (waiters << kSignalShift) | kStackMask;</div>
<div class="line"><a id="l00146" name="l00146"></a><span class="lineno"> 146</span> } <span class="keywordflow">else</span> <span class="keywordflow">if</span> (signals < waiters) {</div>
<div class="line"><a id="l00147" name="l00147"></a><span class="lineno"> 147</span> <span class="comment">// There is a thread in pre-wait state, unblock it.</span></div>
<div class="line"><a id="l00148" name="l00148"></a><span class="lineno"> 148</span> newstate = state + kSignalInc;</div>
<div class="line"><a id="l00149" name="l00149"></a><span class="lineno"> 149</span> } <span class="keywordflow">else</span> {</div>
<div class="line"><a id="l00150" name="l00150"></a><span class="lineno"> 150</span> <span class="comment">// Pop a waiter from list and unpark it.</span></div>
<div class="line"><a id="l00151" name="l00151"></a><span class="lineno"> 151</span> Waiter* w = &waiters_[state & kStackMask];</div>
<div class="line"><a id="l00152" name="l00152"></a><span class="lineno"> 152</span> uint64_t next = w->next.load(std::memory_order_relaxed);</div>
<div class="line"><a id="l00153" name="l00153"></a><span class="lineno"> 153</span> newstate = (state & (kWaiterMask | kSignalMask)) | next;</div>
<div class="line"><a id="l00154" name="l00154"></a><span class="lineno"> 154</span> }</div>
<div class="line"><a id="l00155" name="l00155"></a><span class="lineno"> 155</span> CheckState(newstate);</div>
<div class="line"><a id="l00156" name="l00156"></a><span class="lineno"> 156</span> <span class="keywordflow">if</span> (state_.compare_exchange_weak(state, newstate,</div>
<div class="line"><a id="l00157" name="l00157"></a><span class="lineno"> 157</span> std::memory_order_acq_rel)) {</div>
<div class="line"><a id="l00158" name="l00158"></a><span class="lineno"> 158</span> <span class="keywordflow">if</span> (!notifyAll && (signals < waiters))</div>
<div class="line"><a id="l00159" name="l00159"></a><span class="lineno"> 159</span> <span class="keywordflow">return</span>; <span class="comment">// unblocked pre-wait thread</span></div>
<div class="line"><a id="l00160" name="l00160"></a><span class="lineno"> 160</span> <span class="keywordflow">if</span> ((state & kStackMask) == kStackMask) <span class="keywordflow">return</span>;</div>
<div class="line"><a id="l00161" name="l00161"></a><span class="lineno"> 161</span> Waiter* w = &waiters_[state & kStackMask];</div>
<div class="line"><a id="l00162" name="l00162"></a><span class="lineno"> 162</span> <span class="keywordflow">if</span> (!notifyAll) w->next.store(kStackMask, std::memory_order_relaxed);</div>
<div class="line"><a id="l00163" name="l00163"></a><span class="lineno"> 163</span> Unpark(w);</div>
<div class="line"><a id="l00164" name="l00164"></a><span class="lineno"> 164</span> <span class="keywordflow">return</span>;</div>
<div class="line"><a id="l00165" name="l00165"></a><span class="lineno"> 165</span> }</div>
<div class="line"><a id="l00166" name="l00166"></a><span class="lineno"> 166</span> }</div>
<div class="line"><a id="l00167" name="l00167"></a><span class="lineno"> 167</span> }</div>
<div class="line"><a id="l00168" name="l00168"></a><span class="lineno"> 168</span> </div>
<div class="line"><a id="l00169" name="l00169"></a><span class="lineno"> 169</span> <span class="keyword">class </span>Waiter {</div>
<div class="line"><a id="l00170" name="l00170"></a><span class="lineno"> 170</span> <span class="keyword">friend</span> <span class="keyword">class </span>EventCount;</div>
<div class="line"><a id="l00171" name="l00171"></a><span class="lineno"> 171</span> <span class="comment">// Align to 128 byte boundary to prevent false sharing with other Waiter</span></div>
<div class="line"><a id="l00172" name="l00172"></a><span class="lineno"> 172</span> <span class="comment">// objects in the same vector.</span></div>
<div class="line"><a id="l00173" name="l00173"></a><span class="lineno"> 173</span> EIGEN_ALIGN_TO_BOUNDARY(128) std::atomic<uint64_t> next;</div>
<div class="line"><a id="l00174" name="l00174"></a><span class="lineno"> 174</span> EIGEN_MUTEX mu;</div>
<div class="line"><a id="l00175" name="l00175"></a><span class="lineno"> 175</span> EIGEN_CONDVAR cv;</div>
<div class="line"><a id="l00176" name="l00176"></a><span class="lineno"> 176</span> uint64_t epoch = 0;</div>
<div class="line"><a id="l00177" name="l00177"></a><span class="lineno"> 177</span> <span class="keywordtype">unsigned</span> state = kNotSignaled;</div>
<div class="line"><a id="l00178" name="l00178"></a><span class="lineno"> 178</span> enum {</div>
<div class="line"><a id="l00179" name="l00179"></a><span class="lineno"> 179</span> kNotSignaled,</div>
<div class="line"><a id="l00180" name="l00180"></a><span class="lineno"> 180</span> kWaiting,</div>
<div class="line"><a id="l00181" name="l00181"></a><span class="lineno"> 181</span> kSignaled,</div>
<div class="line"><a id="l00182" name="l00182"></a><span class="lineno"> 182</span> };</div>
<div class="line"><a id="l00183" name="l00183"></a><span class="lineno"> 183</span> };</div>
<div class="line"><a id="l00184" name="l00184"></a><span class="lineno"> 184</span> </div>
<div class="line"><a id="l00185" name="l00185"></a><span class="lineno"> 185</span> <span class="keyword">private</span>:</div>
<div class="line"><a id="l00186" name="l00186"></a><span class="lineno"> 186</span> <span class="comment">// State_ layout:</span></div>
<div class="line"><a id="l00187" name="l00187"></a><span class="lineno"> 187</span> <span class="comment">// - low kWaiterBits is a stack of waiters committed wait</span></div>
<div class="line"><a id="l00188" name="l00188"></a><span class="lineno"> 188</span> <span class="comment">// (indexes in waiters_ array are used as stack elements,</span></div>
<div class="line"><a id="l00189" name="l00189"></a><span class="lineno"> 189</span> <span class="comment">// kStackMask means empty stack).</span></div>
<div class="line"><a id="l00190" name="l00190"></a><span class="lineno"> 190</span> <span class="comment">// - next kWaiterBits is count of waiters in prewait state.</span></div>
<div class="line"><a id="l00191" name="l00191"></a><span class="lineno"> 191</span> <span class="comment">// - next kWaiterBits is count of pending signals.</span></div>
<div class="line"><a id="l00192" name="l00192"></a><span class="lineno"> 192</span> <span class="comment">// - remaining bits are ABA counter for the stack.</span></div>
<div class="line"><a id="l00193" name="l00193"></a><span class="lineno"> 193</span> <span class="comment">// (stored in Waiter node and incremented on push).</span></div>
<div class="line"><a id="l00194" name="l00194"></a><span class="lineno"> 194</span> <span class="keyword">static</span> <span class="keyword">const</span> uint64_t kWaiterBits = 14;</div>
<div class="line"><a id="l00195" name="l00195"></a><span class="lineno"> 195</span> <span class="keyword">static</span> <span class="keyword">const</span> uint64_t kStackMask = (1ull << kWaiterBits) - 1;</div>
<div class="line"><a id="l00196" name="l00196"></a><span class="lineno"> 196</span> <span class="keyword">static</span> <span class="keyword">const</span> uint64_t kWaiterShift = kWaiterBits;</div>
<div class="line"><a id="l00197" name="l00197"></a><span class="lineno"> 197</span> <span class="keyword">static</span> <span class="keyword">const</span> uint64_t kWaiterMask = ((1ull << kWaiterBits) - 1)</div>
<div class="line"><a id="l00198" name="l00198"></a><span class="lineno"> 198</span> << kWaiterShift;</div>
<div class="line"><a id="l00199" name="l00199"></a><span class="lineno"> 199</span> <span class="keyword">static</span> <span class="keyword">const</span> uint64_t kWaiterInc = 1ull << kWaiterShift;</div>
<div class="line"><a id="l00200" name="l00200"></a><span class="lineno"> 200</span> <span class="keyword">static</span> <span class="keyword">const</span> uint64_t kSignalShift = 2 * kWaiterBits;</div>
<div class="line"><a id="l00201" name="l00201"></a><span class="lineno"> 201</span> <span class="keyword">static</span> <span class="keyword">const</span> uint64_t kSignalMask = ((1ull << kWaiterBits) - 1)</div>
<div class="line"><a id="l00202" name="l00202"></a><span class="lineno"> 202</span> << kSignalShift;</div>
<div class="line"><a id="l00203" name="l00203"></a><span class="lineno"> 203</span> <span class="keyword">static</span> <span class="keyword">const</span> uint64_t kSignalInc = 1ull << kSignalShift;</div>
<div class="line"><a id="l00204" name="l00204"></a><span class="lineno"> 204</span> <span class="keyword">static</span> <span class="keyword">const</span> uint64_t kEpochShift = 3 * kWaiterBits;</div>
<div class="line"><a id="l00205" name="l00205"></a><span class="lineno"> 205</span> <span class="keyword">static</span> <span class="keyword">const</span> uint64_t kEpochBits = 64 - kEpochShift;</div>
<div class="line"><a id="l00206" name="l00206"></a><span class="lineno"> 206</span> <span class="keyword">static</span> <span class="keyword">const</span> uint64_t kEpochMask = ((1ull << kEpochBits) - 1) << kEpochShift;</div>
<div class="line"><a id="l00207" name="l00207"></a><span class="lineno"> 207</span> <span class="keyword">static</span> <span class="keyword">const</span> uint64_t kEpochInc = 1ull << kEpochShift;</div>
<div class="line"><a id="l00208" name="l00208"></a><span class="lineno"> 208</span> std::atomic<uint64_t> state_;</div>
<div class="line"><a id="l00209" name="l00209"></a><span class="lineno"> 209</span> MaxSizeVector<Waiter>& waiters_;</div>
<div class="line"><a id="l00210" name="l00210"></a><span class="lineno"> 210</span> </div>
<div class="line"><a id="l00211" name="l00211"></a><span class="lineno"> 211</span> <span class="keyword">static</span> <span class="keywordtype">void</span> CheckState(uint64_t state, <span class="keywordtype">bool</span> waiter = <span class="keyword">false</span>) {</div>
<div class="line"><a id="l00212" name="l00212"></a><span class="lineno"> 212</span> <span class="keyword">static_assert</span>(kEpochBits >= 20, <span class="stringliteral">"not enough bits to prevent ABA problem"</span>);</div>
<div class="line"><a id="l00213" name="l00213"></a><span class="lineno"> 213</span> <span class="keyword">const</span> uint64_t waiters = (state & kWaiterMask) >> kWaiterShift;</div>
<div class="line"><a id="l00214" name="l00214"></a><span class="lineno"> 214</span> <span class="keyword">const</span> uint64_t signals = (state & kSignalMask) >> kSignalShift;</div>
<div class="line"><a id="l00215" name="l00215"></a><span class="lineno"> 215</span> eigen_plain_assert(waiters >= signals);</div>
<div class="line"><a id="l00216" name="l00216"></a><span class="lineno"> 216</span> eigen_plain_assert(waiters < (1 << kWaiterBits) - 1);</div>
<div class="line"><a id="l00217" name="l00217"></a><span class="lineno"> 217</span> eigen_plain_assert(!waiter || waiters > 0);</div>
<div class="line"><a id="l00218" name="l00218"></a><span class="lineno"> 218</span> (void)waiters;</div>
<div class="line"><a id="l00219" name="l00219"></a><span class="lineno"> 219</span> (void)signals;</div>
<div class="line"><a id="l00220" name="l00220"></a><span class="lineno"> 220</span> }</div>
<div class="line"><a id="l00221" name="l00221"></a><span class="lineno"> 221</span> </div>
<div class="line"><a id="l00222" name="l00222"></a><span class="lineno"> 222</span> <span class="keywordtype">void</span> Park(Waiter* w) {</div>
<div class="line"><a id="l00223" name="l00223"></a><span class="lineno"> 223</span> EIGEN_MUTEX_LOCK lock(w->mu);</div>
<div class="line"><a id="l00224" name="l00224"></a><span class="lineno"> 224</span> <span class="keywordflow">while</span> (w->state != Waiter::kSignaled) {</div>
<div class="line"><a id="l00225" name="l00225"></a><span class="lineno"> 225</span> w->state = Waiter::kWaiting;</div>
<div class="line"><a id="l00226" name="l00226"></a><span class="lineno"> 226</span> w->cv.wait(lock);</div>
<div class="line"><a id="l00227" name="l00227"></a><span class="lineno"> 227</span> }</div>
<div class="line"><a id="l00228" name="l00228"></a><span class="lineno"> 228</span> }</div>
<div class="line"><a id="l00229" name="l00229"></a><span class="lineno"> 229</span> </div>
<div class="line"><a id="l00230" name="l00230"></a><span class="lineno"> 230</span> <span class="keywordtype">void</span> Unpark(Waiter* w) {</div>
<div class="line"><a id="l00231" name="l00231"></a><span class="lineno"> 231</span> <span class="keywordflow">for</span> (Waiter* next; w; w = next) {</div>
<div class="line"><a id="l00232" name="l00232"></a><span class="lineno"> 232</span> uint64_t wnext = w->next.load(std::memory_order_relaxed) & kStackMask;</div>
<div class="line"><a id="l00233" name="l00233"></a><span class="lineno"> 233</span> next = wnext == kStackMask ? nullptr : &waiters_[internal::convert_index<size_t>(wnext)];</div>
<div class="line"><a id="l00234" name="l00234"></a><span class="lineno"> 234</span> <span class="keywordtype">unsigned</span> state;</div>
<div class="line"><a id="l00235" name="l00235"></a><span class="lineno"> 235</span> {</div>
<div class="line"><a id="l00236" name="l00236"></a><span class="lineno"> 236</span> EIGEN_MUTEX_LOCK lock(w->mu);</div>
<div class="line"><a id="l00237" name="l00237"></a><span class="lineno"> 237</span> state = w->state;</div>
<div class="line"><a id="l00238" name="l00238"></a><span class="lineno"> 238</span> w->state = Waiter::kSignaled;</div>
<div class="line"><a id="l00239" name="l00239"></a><span class="lineno"> 239</span> }</div>
<div class="line"><a id="l00240" name="l00240"></a><span class="lineno"> 240</span> <span class="comment">// Avoid notifying if it wasn't waiting.</span></div>
<div class="line"><a id="l00241" name="l00241"></a><span class="lineno"> 241</span> <span class="keywordflow">if</span> (state == Waiter::kWaiting) w->cv.notify_one();</div>
<div class="line"><a id="l00242" name="l00242"></a><span class="lineno"> 242</span> }</div>
<div class="line"><a id="l00243" name="l00243"></a><span class="lineno"> 243</span> }</div>
<div class="line"><a id="l00244" name="l00244"></a><span class="lineno"> 244</span> </div>
<div class="line"><a id="l00245" name="l00245"></a><span class="lineno"> 245</span> EventCount(<span class="keyword">const</span> EventCount&) = <span class="keyword">delete</span>;</div>
<div class="line"><a id="l00246" name="l00246"></a><span class="lineno"> 246</span> <span class="keywordtype">void</span> operator=(<span class="keyword">const</span> EventCount&) = <span class="keyword">delete</span>;</div>
<div class="line"><a id="l00247" name="l00247"></a><span class="lineno"> 247</span>};</div>
<div class="line"><a id="l00248" name="l00248"></a><span class="lineno"> 248</span> </div>
<div class="line"><a id="l00249" name="l00249"></a><span class="lineno"> 249</span>} <span class="comment">// namespace Eigen</span></div>
<div class="line"><a id="l00250" name="l00250"></a><span class="lineno"> 250</span> </div>
<div class="line"><a id="l00251" name="l00251"></a><span class="lineno"> 251</span><span class="preprocessor">#endif </span><span class="comment">// EIGEN_CXX11_THREADPOOL_EVENTCOUNT_H</span></div>
<div class="ttc" id="anamespaceEigen_html"><div class="ttname"><a href="namespaceEigen.html">Eigen</a></div><div class="ttdoc">Namespace containing all symbols from the Eigen library.</div><div class="ttdef"><b>Definition</b> Core:139</div></div>
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