<h1 id="basic">Basic<a aria-hidden="true" class="anchor-heading icon-link" href="#basic"></a></h1>
<h1 id="classical-non-distributed-concurrency-control">Classical Non-Distributed Concurrency Control<a aria-hidden="true" class="anchor-heading icon-link" href="#classical-non-distributed-concurrency-control"></a></h1>
<h2 id="spin-lock">spin-lock<a aria-hidden="true" class="anchor-heading icon-link" href="#spin-lock"></a></h2>
<ul>
<li><strong>what</strong>:Atomic compare-and-swap/test-and-set instructions</li>
<li><strong>why</strong>: easy</li>
<li><strong>how</strong>: Requires locking memory bus on multi-core/multi-processor</li>
<li><strong>problem</strong>:Busy wait not good for high contention. busy-waiting, busy-looping or spinning is a technique in which a process repeatedly checks to see if a condition is true, such as whether keyboard input or a lock is available.</li>
</ul>
<h2 id="mutex">mutex<a aria-hidden="true" class="anchor-heading icon-link" href="#mutex"></a></h2>
<ul>
<li><strong>what</strong>:Semaphores, At-Most-N policies,Mutual Exclusion</li>
<li><strong>why</strong>:Conceptually,manages a pool of resources.</li>
<li><strong>how</strong>:
<ul>
<li>P operation: Wait for resource to be available (lock s-=1)</li>
<li>V operation: Make resource available (unlock s+=1)</li>
<li>Deschedule (move to blocked queue) blocked thread or process </li>
<li>Reschedule (move to ready queue) when resource available</li>
<li>初始s=1，s不会是负值</li>
</ul>
</li>
</ul>
<h2 id="condition-variables">CONDITION VARIABLES<a aria-hidden="true" class="anchor-heading icon-link" href="#condition-variables"></a></h2>
<p>Event based </p>
<ul>
<li>Wait – always waits. No predicate</li>
<li>Signal – Wake up a waiter</li>
<li>Broadcast – Wake up all waiters.</li>
</ul>