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</pre><pre class="rust ">
<span class="doccomment">//! A queue-backed read/write data lock.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! As with any queue-backed system, deadlocks must be carefully avoided when</span>
<span class="doccomment">//! interoperating with other queues.</span>
<span class="doccomment">//!</span>
<span class="comment">//</span>
<span class="comment">// * It is unclear how many of the unsafe methods within need actually remain</span>
<span class="comment">// unsafe.</span>
<span class="comment">// * Virtually every aspect of each of the types in this module would benefit</span>
<span class="comment">// from simplifying refactoring.</span>
<span class="comment">// - Locking for processing, looping, and resetting the processing flag all</span>
<span class="comment">// need to be standardized (factored out).</span>
<span class="comment">// * Evaluate whether or not sleeping when the lock is contended (`CONTENDED`</span>
<span class="comment">// bit) is the best approach. This may be slower than it needs to be when</span>
<span class="comment">// multiple cores are concurrently attempting to access. Use</span>
<span class="comment">// `thread::yield_now()` instead? Spin a few times first? Whatever. [UPDATE:</span>
<span class="comment">// Doing some spinning now]</span>
<span class="comment">//</span>
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">ops</span>::{<span class="ident">Deref</span>, <span class="ident">DerefMut</span>};
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">sync</span>::<span class="ident">Arc</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">sync</span>::<span class="ident">atomic</span>::{<span class="ident">fence</span>, <span class="ident">AtomicUsize</span>};
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">sync</span>::<span class="ident">atomic</span>::<span class="ident">Ordering</span>::{<span class="ident">SeqCst</span>, <span class="ident">Acquire</span>, <span class="comment">/*Release*/</span>};
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">cell</span>::<span class="ident">UnsafeCell</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">thread</span>;
<span class="kw">use</span> <span class="ident">futures</span>::{<span class="ident">Future</span>, <span class="ident">Poll</span>, <span class="ident">Canceled</span>, <span class="ident">Async</span>};
<span class="kw">use</span> <span class="ident">futures</span>::<span class="ident">sync</span>::<span class="ident">oneshot</span>::{<span class="self">self</span>, <span class="ident">Sender</span>, <span class="ident">Receiver</span>};
<span class="kw">use</span> <span class="ident">crossbeam</span>::<span class="ident">sync</span>::<span class="ident">SegQueue</span>;
<span class="kw">const</span> <span class="ident">READ_COUNT_MASK</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">0x00FFFFFF</span>;
<span class="kw">const</span> <span class="ident">WRITE_LOCKED</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">1</span> <span class="op"><<</span> <span class="number">24</span>;
<span class="kw">const</span> <span class="ident">CONTENDED</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">1</span> <span class="op"><<</span> <span class="number">25</span>;
<span class="kw">const</span> <span class="ident">PRINT_DEBUG</span>: <span class="ident">bool</span> <span class="op">=</span> <span class="bool-val">false</span>;
<span class="doccomment">/// Our currently favored thread 'chill out' method used when multiple threads</span>
<span class="doccomment">/// are attempting to contend concurrently.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">chill_out</span>() {
<span class="comment">// thread::sleep(::std::time::Duration::new(0, 1));</span>
<span class="ident">thread</span>::<span class="ident">yield_now</span>();
<span class="comment">// NOTE: It's possible that sleeping or yielding here prolongs the time it</span>
<span class="comment">// takes to process the queue to an unreasonable degree. There may be an</span>
<span class="comment">// efficiency vs. duration balance to strike here (compared to spinning).</span>
}
<span class="doccomment">/// Extracts a `QrwLock` from a guard of either type.</span>
<span class="comment">//</span>
<span class="comment">// This saves us two unnecessary atomic stores (the reference count of lock</span>
<span class="comment">// going up then down when releasing or up/downgrading) which would occur if</span>
<span class="comment">// we were to clone then drop.</span>
<span class="comment">//</span>
<span class="comment">// QUESTION: Is there a more elegant way to do this?</span>
<span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">extract_lock</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">G</span>: <span class="ident">Guard</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span>(<span class="ident">guard</span>: <span class="ident">G</span>) <span class="op">-></span> <span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">let</span> <span class="ident">lock</span> <span class="op">=</span> ::<span class="ident">std</span>::<span class="ident">ptr</span>::<span class="ident">read</span>(<span class="ident">guard</span>.<span class="ident">lock</span>());
::<span class="ident">std</span>::<span class="ident">mem</span>::<span class="ident">forget</span>(<span class="ident">guard</span>);
<span class="ident">lock</span>
}
<span class="doccomment">/// Very forgettable guards.</span>
<span class="kw">trait</span> <span class="ident">Guard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">where</span> <span class="self">Self</span>: ::<span class="ident">std</span>::<span class="ident">marker</span>::<span class="ident">Sized</span> {
<span class="kw">fn</span> <span class="ident">lock</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>;
<span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">forget</span>(<span class="self">self</span>) {
::<span class="ident">std</span>::<span class="ident">mem</span>::<span class="ident">forget</span>(<span class="self">self</span>);
}
}
<span class="doccomment">/// Allows read-only access to the data contained within a lock.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">ReadGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">lock</span>: <span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">ReadGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">upgrade</span>(<span class="ident">guard</span>: <span class="ident">ReadGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) <span class="op">-></span> <span class="ident">FutureUpgrade</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="ident">guard</span>.<span class="ident">lock</span>.<span class="ident">read_count</span>().<span class="ident">unwrap</span>() <span class="op">></span> <span class="number">0</span>);
<span class="kw">match</span> <span class="kw">unsafe</span> { <span class="ident">guard</span>.<span class="ident">lock</span>.<span class="ident">upgrade_read_lock</span>() } {
<span class="prelude-val">Ok</span>(_) <span class="op">=></span> {
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"ReadGuard::upgrade: Read lock is now upgraded (thread: {}) ..."</span>,
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="kw">unsafe</span> { <span class="ident">FutureUpgrade</span>::<span class="ident">new</span>(<span class="ident">extract_lock</span>(<span class="ident">guard</span>), <span class="prelude-val">None</span>) }
},
<span class="prelude-val">Err</span>(<span class="ident">rx</span>) <span class="op">=></span> {
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"ReadGuard::upgrade: Waiting for the read count to reach 1 (thread: {}) ..."</span>,
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="kw">unsafe</span> { <span class="ident">FutureUpgrade</span>::<span class="ident">new</span>(<span class="ident">extract_lock</span>(<span class="ident">guard</span>), <span class="prelude-val">Some</span>(<span class="ident">rx</span>)) }
}
}
}
<span class="doccomment">/// Releases the lock held by this `ReadGuard` and returns the original `QrwLock`.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">release</span>(<span class="ident">guard</span>: <span class="ident">ReadGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) <span class="op">-></span> <span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">unsafe</span> {
<span class="ident">guard</span>.<span class="ident">lock</span>.<span class="ident">release_read_lock</span>();
<span class="ident">extract_lock</span>(<span class="ident">guard</span>)
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Deref</span> <span class="kw">for</span> <span class="ident">ReadGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Target</span> <span class="op">=</span> <span class="ident">T</span>;
<span class="kw">fn</span> <span class="ident">deref</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">T</span> {
<span class="kw">unsafe</span> { <span class="kw-2">&</span><span class="kw-2">*</span><span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">inner</span>.<span class="ident">cell</span>.<span class="ident">get</span>() }
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Drop</span> <span class="kw">for</span> <span class="ident">ReadGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">drop</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) {
<span class="kw">unsafe</span> { <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">release_read_lock</span>() }
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Guard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">for</span> <span class="ident">ReadGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">lock</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw-2">&</span><span class="self">self</span>.<span class="ident">lock</span>
}
}
<span class="doccomment">/// Allows read or write access to the data contained within a lock.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">WriteGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">lock</span>: <span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">WriteGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Converts this `WriteGuard` into a `ReadGuard` and fulfills any other</span>
<span class="doccomment">/// pending read requests.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">downgrade</span>(<span class="ident">guard</span>: <span class="ident">WriteGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) <span class="op">-></span> <span class="ident">ReadGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">unsafe</span> {
<span class="ident">guard</span>.<span class="ident">lock</span>.<span class="ident">downgrade_write_lock</span>();
<span class="ident">ReadGuard</span> { <span class="ident">lock</span>: <span class="ident">extract_lock</span>(<span class="ident">guard</span>) }
}
}
<span class="doccomment">/// Releases the lock held by this `WriteGuard` and returns the original</span>
<span class="doccomment">/// `QrwLock`.</span>
<span class="comment">//</span>
<span class="comment">// * TODO: Create a test that ensures the write lock is released.</span>
<span class="comment">// Commenting out the `release_write_lock()' line appears to have no</span>
<span class="comment">// effect on the outcome of the current tests.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">release</span>(<span class="ident">guard</span>: <span class="ident">WriteGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) <span class="op">-></span> <span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">unsafe</span> {
<span class="ident">guard</span>.<span class="ident">lock</span>.<span class="ident">release_write_lock</span>();
<span class="ident">extract_lock</span>(<span class="ident">guard</span>)
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Deref</span> <span class="kw">for</span> <span class="ident">WriteGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Target</span> <span class="op">=</span> <span class="ident">T</span>;
<span class="kw">fn</span> <span class="ident">deref</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">T</span> {
<span class="kw">unsafe</span> { <span class="kw-2">&</span><span class="kw-2">*</span><span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">inner</span>.<span class="ident">cell</span>.<span class="ident">get</span>() }
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">DerefMut</span> <span class="kw">for</span> <span class="ident">WriteGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">deref_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">T</span> {
<span class="kw">unsafe</span> { <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">inner</span>.<span class="ident">cell</span>.<span class="ident">get</span>() }
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Drop</span> <span class="kw">for</span> <span class="ident">WriteGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">drop</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) {
<span class="kw">unsafe</span> { <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">release_write_lock</span>() }
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Guard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">for</span> <span class="ident">WriteGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">lock</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw-2">&</span><span class="self">self</span>.<span class="ident">lock</span>
}
}
<span class="doccomment">/// A precursor to a `WriteGuard`.</span>
<span class="attribute">#[<span class="ident">must_use</span> <span class="op">=</span> <span class="string">"futures do nothing unless polled"</span>]</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">FutureUpgrade</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">lock</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span>,
<span class="comment">// Designates whether or not to resolve immediately:</span>
<span class="ident">rx</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Receiver</span><span class="op"><</span>()<span class="op">>></span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">FutureUpgrade</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Returns a new `FutureUpgrade`.</span>
<span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">lock</span>: <span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>, <span class="ident">rx</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Receiver</span><span class="op"><</span>()<span class="op">>></span>) <span class="op">-></span> <span class="ident">FutureUpgrade</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">FutureUpgrade</span> {
<span class="ident">lock</span>: <span class="prelude-val">Some</span>(<span class="ident">lock</span>),
<span class="ident">rx</span>: <span class="ident">rx</span>,
}
}
<span class="doccomment">/// Blocks the current thread until this future resolves.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">wait</span>(<span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">WriteGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>, <span class="ident">Canceled</span><span class="op">></span> {
<span class="op"><</span><span class="self">Self</span> <span class="kw">as</span> <span class="ident">Future</span><span class="op">></span>::<span class="ident">wait</span>(<span class="self">self</span>)
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Future</span> <span class="kw">for</span> <span class="ident">FutureUpgrade</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="ident">WriteGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>;
<span class="kw">type</span> <span class="ident">Error</span> <span class="op">=</span> <span class="ident">Canceled</span>;
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">poll</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">Poll</span><span class="op"><</span><span class="self">Self</span>::<span class="ident">Item</span>, <span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span> {
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">is_some</span>() {
<span class="comment">// FUTURE NOTE: Lexical borrowing should allow this to be</span>
<span class="comment">// restructured without the extra `.unwrap()` below.</span>
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">rx</span>.<span class="ident">is_none</span>() {
<span class="comment">// fence(SeqCst);</span>
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"FutureUpgrade::poll: Uncontended. Upgrading. (thread: {})"</span>,
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="prelude-val">Ok</span>(<span class="ident">Async</span>::<span class="ident">Ready</span>(<span class="ident">WriteGuard</span> { <span class="ident">lock</span>: <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">take</span>().<span class="ident">unwrap</span>() }))
} <span class="kw">else</span> {
<span class="kw">unsafe</span> { <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">as_ref</span>().<span class="ident">unwrap</span>().<span class="ident">process_queues</span>() }
<span class="self">self</span>.<span class="ident">rx</span>.<span class="ident">as_mut</span>().<span class="ident">unwrap</span>().<span class="ident">poll</span>().<span class="ident">map</span>(<span class="op">|</span><span class="ident">res</span><span class="op">|</span> <span class="ident">res</span>.<span class="ident">map</span>(<span class="op">|</span>_<span class="op">|</span> {
<span class="comment">// fence(SeqCst);</span>
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"FutureUpgrade::poll: Ready. Upgrading. (thread: {})"</span>,
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="ident">WriteGuard</span> { <span class="ident">lock</span>: <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">take</span>().<span class="ident">unwrap</span>() }
}))
}
} <span class="kw">else</span> {
<span class="macro">panic</span><span class="macro">!</span>(<span class="string">"FutureUpgrade::poll: Task already completed."</span>);
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Drop</span> <span class="kw">for</span> <span class="ident">FutureUpgrade</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Gracefully unlock if this guard has a lock acquired.</span>
<span class="kw">fn</span> <span class="ident">drop</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) {
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">lock</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">take</span>() {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">rx</span>.<span class="ident">take</span>() {
<span class="prelude-val">Some</span>(<span class="kw-2">mut</span> <span class="ident">rx</span>) <span class="op">=></span> {
<span class="ident">rx</span>.<span class="ident">close</span>();
<span class="kw">match</span> <span class="ident">rx</span>.<span class="ident">poll</span>() {
<span class="prelude-val">Ok</span>(<span class="ident">status</span>) <span class="op">=></span> {
<span class="kw">match</span> <span class="ident">status</span> {
<span class="ident">Async</span>::<span class="ident">Ready</span>(_) <span class="op">=></span> {
<span class="kw">unsafe</span> { <span class="ident">lock</span>.<span class="ident">release_write_lock</span>() }
},
<span class="ident">Async</span>::<span class="ident">NotReady</span> <span class="op">=></span> (),
}
},
<span class="prelude-val">Err</span>(_) <span class="op">=></span> (),
}
},
<span class="prelude-val">None</span> <span class="op">=></span> <span class="kw">unsafe</span> { <span class="ident">lock</span>.<span class="ident">release_write_lock</span>() },
}
}
}
}
<span class="doccomment">/// A future which resolves to a `ReadGuard`.</span>
<span class="attribute">#[<span class="ident">must_use</span> <span class="op">=</span> <span class="string">"futures do nothing unless polled"</span>]</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">FutureReadGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">lock</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span>,
<span class="ident">rx</span>: <span class="ident">Receiver</span><span class="op"><</span>()<span class="op">></span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">FutureReadGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Returns a new `FutureReadGuard`.</span>
<span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">lock</span>: <span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>, <span class="ident">rx</span>: <span class="ident">Receiver</span><span class="op"><</span>()<span class="op">></span>) <span class="op">-></span> <span class="ident">FutureReadGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">FutureReadGuard</span> {
<span class="ident">lock</span>: <span class="prelude-val">Some</span>(<span class="ident">lock</span>),
<span class="ident">rx</span>: <span class="ident">rx</span>,
}
}
<span class="doccomment">/// Blocks the current thread until this future resolves.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">wait</span>(<span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">ReadGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>, <span class="ident">Canceled</span><span class="op">></span> {
<span class="op"><</span><span class="self">Self</span> <span class="kw">as</span> <span class="ident">Future</span><span class="op">></span>::<span class="ident">wait</span>(<span class="self">self</span>)
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Future</span> <span class="kw">for</span> <span class="ident">FutureReadGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="ident">ReadGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>;
<span class="kw">type</span> <span class="ident">Error</span> <span class="op">=</span> <span class="ident">Canceled</span>;
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">poll</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">Poll</span><span class="op"><</span><span class="self">Self</span>::<span class="ident">Item</span>, <span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span> {
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">is_some</span>() {
<span class="kw">unsafe</span> { <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">as_ref</span>().<span class="ident">unwrap</span>().<span class="ident">process_queues</span>() }
<span class="self">self</span>.<span class="ident">rx</span>.<span class="ident">poll</span>().<span class="ident">map</span>(<span class="op">|</span><span class="ident">res</span><span class="op">|</span> <span class="ident">res</span>.<span class="ident">map</span>(<span class="op">|</span>_<span class="op">|</span> {
<span class="comment">// fence(SeqCst);</span>
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"FutureReadGuard::poll: ReadGuard acquired. (thread: {})"</span>,
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="ident">ReadGuard</span> { <span class="ident">lock</span>: <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">take</span>().<span class="ident">unwrap</span>() }
}))
} <span class="kw">else</span> {
<span class="macro">panic</span><span class="macro">!</span>(<span class="string">"FutureReadGuard::poll: Task already completed."</span>);
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Drop</span> <span class="kw">for</span> <span class="ident">FutureReadGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Gracefully unlock if this guard has a lock acquired.</span>
<span class="kw">fn</span> <span class="ident">drop</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) {
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">lock</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">take</span>() {
<span class="self">self</span>.<span class="ident">rx</span>.<span class="ident">close</span>();
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">rx</span>.<span class="ident">poll</span>() {
<span class="prelude-val">Ok</span>(<span class="ident">status</span>) <span class="op">=></span> {
<span class="kw">match</span> <span class="ident">status</span> {
<span class="ident">Async</span>::<span class="ident">Ready</span>(_) <span class="op">=></span> {
<span class="kw">unsafe</span> { <span class="ident">lock</span>.<span class="ident">release_read_lock</span>() }
},
<span class="ident">Async</span>::<span class="ident">NotReady</span> <span class="op">=></span> (),
}
},
<span class="prelude-val">Err</span>(_) <span class="op">=></span> (),
}
}
}
}
<span class="doccomment">/// A future which resolves to a `WriteGuard`.</span>
<span class="attribute">#[<span class="ident">must_use</span> <span class="op">=</span> <span class="string">"futures do nothing unless polled"</span>]</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">FutureWriteGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">lock</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span>,
<span class="ident">rx</span>: <span class="ident">Receiver</span><span class="op"><</span>()<span class="op">></span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">FutureWriteGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Returns a new `FutureWriteGuard`.</span>
<span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">lock</span>: <span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>, <span class="ident">rx</span>: <span class="ident">Receiver</span><span class="op"><</span>()<span class="op">></span>) <span class="op">-></span> <span class="ident">FutureWriteGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">FutureWriteGuard</span> {
<span class="ident">lock</span>: <span class="prelude-val">Some</span>(<span class="ident">lock</span>),
<span class="ident">rx</span>: <span class="ident">rx</span>,
}
}
<span class="doccomment">/// Blocks the current thread until this future resolves.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">wait</span>(<span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">WriteGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>, <span class="ident">Canceled</span><span class="op">></span> {
<span class="op"><</span><span class="self">Self</span> <span class="kw">as</span> <span class="ident">Future</span><span class="op">></span>::<span class="ident">wait</span>(<span class="self">self</span>)
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Future</span> <span class="kw">for</span> <span class="ident">FutureWriteGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="ident">WriteGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>;
<span class="kw">type</span> <span class="ident">Error</span> <span class="op">=</span> <span class="ident">Canceled</span>;
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">poll</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">Poll</span><span class="op"><</span><span class="self">Self</span>::<span class="ident">Item</span>, <span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span> {
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">is_some</span>() {
<span class="kw">unsafe</span> { <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">as_ref</span>().<span class="ident">unwrap</span>().<span class="ident">process_queues</span>() }
<span class="self">self</span>.<span class="ident">rx</span>.<span class="ident">poll</span>().<span class="ident">map</span>(<span class="op">|</span><span class="ident">res</span><span class="op">|</span> <span class="ident">res</span>.<span class="ident">map</span>(<span class="op">|</span>_<span class="op">|</span> {
<span class="comment">// fence(SeqCst);</span>
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"FutureWriteGuard::poll: WriteGuard acquired. (thread: {})"</span>,
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="ident">WriteGuard</span> { <span class="ident">lock</span>: <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">take</span>().<span class="ident">unwrap</span>() }
}))
} <span class="kw">else</span> {
<span class="macro">panic</span><span class="macro">!</span>(<span class="string">"FutureWriteGuard::poll: Task already completed."</span>);
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Drop</span> <span class="kw">for</span> <span class="ident">FutureWriteGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Gracefully unlock if this guard has a lock acquired.</span>
<span class="kw">fn</span> <span class="ident">drop</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) {
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">lock</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">lock</span>.<span class="ident">take</span>() {
<span class="self">self</span>.<span class="ident">rx</span>.<span class="ident">close</span>();
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">rx</span>.<span class="ident">poll</span>() {
<span class="prelude-val">Ok</span>(<span class="ident">status</span>) <span class="op">=></span> {
<span class="kw">match</span> <span class="ident">status</span> {
<span class="ident">Async</span>::<span class="ident">Ready</span>(_) <span class="op">=></span> {
<span class="kw">unsafe</span> { <span class="ident">lock</span>.<span class="ident">release_write_lock</span>() }
},
<span class="ident">Async</span>::<span class="ident">NotReady</span> <span class="op">=></span> (),
}
},
<span class="prelude-val">Err</span>(_) <span class="op">=></span> (),
}
}
}
}
<span class="doccomment">/// Specifies whether a `QrwRequest` is a read or write request.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>, <span class="ident">Clone</span>, <span class="ident">Copy</span>, <span class="ident">PartialEq</span>, <span class="ident">Eq</span>)]</span>
<span class="kw">pub</span> <span class="kw">enum</span> <span class="ident">RequestKind</span> {
<span class="ident">Read</span>,
<span class="ident">Write</span>,
}
<span class="doccomment">/// A request to lock the lock for either read or write access.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">QrwRequest</span> {
<span class="ident">tx</span>: <span class="ident">Sender</span><span class="op"><</span>()<span class="op">></span>,
<span class="ident">kind</span>: <span class="ident">RequestKind</span>,
}
<span class="kw">impl</span> <span class="ident">QrwRequest</span> {
<span class="doccomment">/// Returns a new `QrwRequest`.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">tx</span>: <span class="ident">Sender</span><span class="op"><</span>()<span class="op">></span>, <span class="ident">kind</span>: <span class="ident">RequestKind</span>) <span class="op">-></span> <span class="ident">QrwRequest</span> {
<span class="ident">QrwRequest</span> {
<span class="ident">tx</span>: <span class="ident">tx</span>,
<span class="ident">kind</span>: <span class="ident">kind</span>,
}
}
}
<span class="doccomment">/// The guts of a `QrwLock`.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">struct</span> <span class="ident">Inner</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="comment">// TODO: Convert to `AtomicBool` if no additional states are needed:</span>
<span class="ident">state</span>: <span class="ident">AtomicUsize</span>,
<span class="ident">cell</span>: <span class="ident">UnsafeCell</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>,
<span class="ident">queue</span>: <span class="ident">SegQueue</span><span class="op"><</span><span class="ident">QrwRequest</span><span class="op">></span>,
<span class="ident">tip</span>: <span class="ident">UnsafeCell</span><span class="op"><</span><span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">QrwRequest</span><span class="op">>></span>,
<span class="comment">// upgrade_tx: UnsafeCell<Option<Sender<()>>>,</span>
<span class="ident">upgrade_queue</span>: <span class="ident">SegQueue</span><span class="op"><</span><span class="ident">Sender</span><span class="op"><</span>()<span class="op">>></span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">From</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">for</span> <span class="ident">Inner</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">from</span>(<span class="ident">val</span>: <span class="ident">T</span>) <span class="op">-></span> <span class="ident">Inner</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">Inner</span> {
<span class="ident">state</span>: <span class="ident">AtomicUsize</span>::<span class="ident">new</span>(<span class="number">0</span>),
<span class="ident">cell</span>: <span class="ident">UnsafeCell</span>::<span class="ident">new</span>(<span class="ident">val</span>),
<span class="ident">queue</span>: <span class="ident">SegQueue</span>::<span class="ident">new</span>(),
<span class="ident">tip</span>: <span class="ident">UnsafeCell</span>::<span class="ident">new</span>(<span class="prelude-val">None</span>),
<span class="comment">// upgrade_tx: UnsafeCell::new(None),</span>
<span class="ident">upgrade_queue</span>: <span class="ident">SegQueue</span>::<span class="ident">new</span>(),
}
}
}
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Send</span><span class="op">></span> <span class="ident">Send</span> <span class="kw">for</span> <span class="ident">Inner</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {}
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Send</span><span class="op">></span> <span class="ident">Sync</span> <span class="kw">for</span> <span class="ident">Inner</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {}
<span class="doccomment">/// A queue-backed read/write data lock.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// As with any queue-backed system, deadlocks must be carefully avoided when</span>
<span class="doccomment">/// interoperating with other queues.</span>
<span class="doccomment">///</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">inner</span>: <span class="ident">Arc</span><span class="op"><</span><span class="ident">Inner</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Creates and returns a new `QrwLock`.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">val</span>: <span class="ident">T</span>) <span class="op">-></span> <span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">QrwLock</span> {
<span class="ident">inner</span>: <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="ident">Inner</span>::<span class="ident">from</span>(<span class="ident">val</span>)),
}
}
<span class="doccomment">/// Returns a new `FutureReadGuard` which can be used as a future and will</span>
<span class="doccomment">/// resolve into a `ReadGuard`.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">read</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">FutureReadGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Requesting read lock.(thread: {}) ..."</span>,
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="kw">let</span> (<span class="ident">tx</span>, <span class="ident">rx</span>) <span class="op">=</span> <span class="ident">oneshot</span>::<span class="ident">channel</span>();
<span class="kw">unsafe</span> { <span class="self">self</span>.<span class="ident">enqueue_lock_request</span>(<span class="ident">QrwRequest</span>::<span class="ident">new</span>(<span class="ident">tx</span>, <span class="ident">RequestKind</span>::<span class="ident">Read</span>)); }
<span class="ident">FutureReadGuard</span>::<span class="ident">new</span>(<span class="self">self</span>, <span class="ident">rx</span>)
}
<span class="doccomment">/// Returns a new `FutureWriteGuard` which can be used as a future and will</span>
<span class="doccomment">/// resolve into a `WriteGuard`.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">write</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">FutureWriteGuard</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Requesting write lock.(thread: {}) ..."</span>,
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="kw">let</span> (<span class="ident">tx</span>, <span class="ident">rx</span>) <span class="op">=</span> <span class="ident">oneshot</span>::<span class="ident">channel</span>();
<span class="kw">unsafe</span> { <span class="self">self</span>.<span class="ident">enqueue_lock_request</span>(<span class="ident">QrwRequest</span>::<span class="ident">new</span>(<span class="ident">tx</span>, <span class="ident">RequestKind</span>::<span class="ident">Write</span>)); }
<span class="ident">FutureWriteGuard</span>::<span class="ident">new</span>(<span class="self">self</span>, <span class="ident">rx</span>)
}
<span class="doccomment">/// Pushes a lock request onto the queue.</span>
<span class="doccomment">///</span>
<span class="comment">//</span>
<span class="comment">// TODO: Evaluate unsafe-ness (appears unlikely this can be misused except</span>
<span class="comment">// to deadlock the queue which is fine).</span>
<span class="comment">//</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">enqueue_lock_request</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">req</span>: <span class="ident">QrwRequest</span>) {
<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">queue</span>.<span class="ident">push</span>(<span class="ident">req</span>);
}
<span class="doccomment">/// Returns a mutable reference to the inner `Vec` if there are currently</span>
<span class="doccomment">/// no other copies of this `QrwLock`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Since this call borrows the inner lock mutably, no actual locking needs to</span>
<span class="doccomment">/// take place---the mutable borrow statically guarantees no locks exist.</span>
<span class="doccomment">///</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">get_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">T</span><span class="op">></span> {
<span class="ident">Arc</span>::<span class="ident">get_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">inner</span>).<span class="ident">map</span>(<span class="op">|</span><span class="ident">inn</span><span class="op">|</span> <span class="kw">unsafe</span> { <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="ident">inn</span>.<span class="ident">cell</span>.<span class="ident">get</span>() })
}
<span class="doccomment">/// Returns a reference to the inner value.</span>
<span class="doccomment">///</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">as_ptr</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">T</span> {
<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">cell</span>.<span class="ident">get</span>()
}
<span class="doccomment">/// Returns a mutable reference to the inner value.</span>
<span class="doccomment">///</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">as_mut_ptr</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span> {
<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">cell</span>.<span class="ident">get</span>()
}
<span class="doccomment">/// Pops the next read or write lock request and returns it or `None` if the queue is empty.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">pop_request</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">QrwRequest</span><span class="op">></span> {
<span class="macro">debug_assert_eq</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">load</span>(<span class="ident">Acquire</span>) <span class="op">&</span> <span class="ident">CONTENDED</span>, <span class="ident">CONTENDED</span>);
<span class="kw">unsafe</span> {
<span class="comment">// Pop twice if the tip was `None` but the queue was not empty.</span>
::<span class="ident">std</span>::<span class="ident">mem</span>::<span class="ident">replace</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">tip</span>.<span class="ident">get</span>(), <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">queue</span>.<span class="ident">try_pop</span>())
.<span class="ident">or_else</span>(<span class="op">||</span> {
<span class="kw">if</span> (<span class="kw-2">*</span><span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">tip</span>.<span class="ident">get</span>()).<span class="ident">is_some</span>() {
<span class="self">self</span>.<span class="ident">pop_request</span>()
} <span class="kw">else</span> {
<span class="prelude-val">None</span>
}
})
}
}
<span class="doccomment">/// Returns the `RequestKind` for the next pending read or write lock request.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">peek_request_kind</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">RequestKind</span><span class="op">></span> {
<span class="macro">debug_assert_eq</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">load</span>(<span class="ident">Acquire</span>) <span class="op">&</span> <span class="ident">CONTENDED</span>, <span class="ident">CONTENDED</span>);
<span class="kw">unsafe</span> {
<span class="kw">if</span> (<span class="kw-2">*</span><span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">tip</span>.<span class="ident">get</span>()).<span class="ident">is_none</span>() {
::<span class="ident">std</span>::<span class="ident">mem</span>::<span class="ident">replace</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">tip</span>.<span class="ident">get</span>(), <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">queue</span>.<span class="ident">try_pop</span>());
}
(<span class="kw-2">*</span><span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">tip</span>.<span class="ident">get</span>()).<span class="ident">as_ref</span>().<span class="ident">map</span>(<span class="op">|</span><span class="ident">req</span><span class="op">|</span> <span class="ident">req</span>.<span class="ident">kind</span>)
}
}
<span class="doccomment">/// Fulfill a request if possible.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">fulfill_request</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="kw-2">mut</span> <span class="ident">state</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="ident">usize</span> {
<span class="kw">loop</span> {
<span class="macro">debug_assert_eq</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">load</span>(<span class="ident">Acquire</span>) <span class="op">&</span> <span class="ident">CONTENDED</span>, <span class="ident">CONTENDED</span>);
<span class="macro">debug_assert_eq</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">load</span>(<span class="ident">Acquire</span>) <span class="op">&</span> <span class="ident">WRITE_LOCKED</span>, <span class="number">0</span>);
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">req</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">pop_request</span>() {
<span class="comment">// If there is a send error, a requester has dropped its</span>
<span class="comment">// receiver so just go to the next, otherwise process.</span>
<span class="kw">if</span> <span class="ident">req</span>.<span class="ident">tx</span>.<span class="ident">send</span>(()).<span class="ident">is_ok</span>() {
<span class="macro">debug_assert_eq</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">load</span>(<span class="ident">Acquire</span>) <span class="op">&</span> <span class="ident">WRITE_LOCKED</span>, <span class="number">0</span>);
<span class="kw">match</span> <span class="ident">req</span>.<span class="ident">kind</span> {
<span class="ident">RequestKind</span>::<span class="ident">Read</span> <span class="op">=></span> {
<span class="ident">state</span> <span class="op">+=</span> <span class="number">1</span>;
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Locked for reading (state: {}) \
(thread: {}) ..."</span>, <span class="ident">state</span>,
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">RequestKind</span>::<span class="ident">Read</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">peek_request_kind</span>() {
<span class="kw">continue</span>;
} <span class="kw">else</span> {
<span class="kw">break</span>;
}
},
<span class="ident">RequestKind</span>::<span class="ident">Write</span> <span class="op">=></span> {
<span class="macro">debug_assert_eq</span><span class="macro">!</span>(<span class="ident">state</span>, <span class="number">0</span>);
<span class="ident">state</span> <span class="op">=</span> <span class="ident">WRITE_LOCKED</span>;
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Locked for writing (state: {}) \
(thread: {}) ..."</span>, <span class="ident">state</span>,
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="kw">break</span>;
},
}
}
} <span class="kw">else</span> {
<span class="kw">break</span>;
}
}
<span class="ident">state</span>
}
<span class="doccomment">/// Returns the current number of read locks.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Currently used for debug purposes only.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">read_count</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> {
<span class="kw">let</span> <span class="ident">state</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">load</span>(<span class="ident">Acquire</span>);
<span class="kw">let</span> <span class="ident">read_count</span> <span class="op">=</span> <span class="ident">state</span> <span class="op">&</span> <span class="ident">READ_COUNT_MASK</span>;
<span class="kw">if</span> <span class="ident">state</span> <span class="op">&</span> <span class="ident">READ_COUNT_MASK</span> <span class="op">==</span> <span class="ident">read_count</span> {
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Read count: {} (thread: {}) ..."</span>, <span class="ident">read_count</span>,
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="prelude-val">Some</span>(<span class="ident">read_count</span> <span class="kw">as</span> <span class="ident">u32</span>)
} <span class="kw">else</span> {
<span class="prelude-val">None</span>
}
}
<span class="doccomment">/// Acquires exclusive access to the lock state and returns it.</span>
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span>
<span class="kw">fn</span> <span class="ident">contend</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">usize</span> {
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Processing state... (thread: {})"</span>,
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">spins</span>: <span class="ident">u32</span> <span class="op">=</span> <span class="number">0</span>;
<span class="kw">loop</span> {
<span class="kw">let</span> <span class="ident">state</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">fetch_or</span>(<span class="ident">CONTENDED</span>, <span class="ident">SeqCst</span>);
<span class="kw">if</span> <span class="ident">state</span> <span class="op">&</span> <span class="ident">CONTENDED</span> <span class="op">!=</span> <span class="number">0</span> {
<span class="kw">if</span> <span class="ident">spins</span> <span class="op">>=</span> <span class="number">16</span> {
<span class="ident">chill_out</span>();
} <span class="kw">else</span> {
<span class="kw">for</span> _ <span class="kw">in</span> <span class="number">0</span>..(<span class="number">2</span> <span class="op"><<</span> <span class="ident">spins</span>) { <span class="ident">fence</span>(<span class="ident">SeqCst</span>); }
}
<span class="ident">spins</span> <span class="op">+=</span> <span class="number">1</span>;
} <span class="kw">else</span> {
<span class="kw">return</span> <span class="ident">state</span>;
}
}
}
<span class="doccomment">/// Fulfills an upgrade request.</span>
<span class="kw">fn</span> <span class="ident">process_upgrade_queue</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Fulfilling upgrade... (thread: {})"</span>,
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">load</span>(<span class="ident">Acquire</span>) <span class="op">==</span> <span class="ident">CONTENDED</span>);
<span class="kw">loop</span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">upgrade_queue</span>.<span class="ident">try_pop</span>() {
<span class="prelude-val">Some</span>(<span class="ident">tx</span>) <span class="op">=></span> {
<span class="kw">match</span> <span class="ident">tx</span>.<span class="ident">send</span>(()) {
<span class="prelude-val">Ok</span>(_) <span class="op">=></span> {
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Upgrading to write lock. \
(thread: {}) ..."</span>, <span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="kw">return</span> <span class="bool-val">true</span>;
},
<span class="prelude-val">Err</span>(()) <span class="op">=></span> {
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Unable to upgrade: error completing oneshot \
(thread: {}) ..."</span>, <span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="kw">continue</span>
},
}
},
<span class="prelude-val">None</span> <span class="op">=></span> <span class="kw">break</span>,
}
}
<span class="bool-val">false</span>
}
<span class="doccomment">/// Pops the next lock request in the queue if possible.</span>
<span class="doccomment">///</span>
<span class="comment">//</span>
<span class="comment">// TODO: Clarify the following (or remove):</span>
<span class="comment">//</span>
<span class="comment">// If this (the caller's?) lock is released, read or write-locks this lock</span>
<span class="comment">// and unparks the next requester task in the queue.</span>
<span class="comment">//</span>
<span class="comment">// If this (the caller's?) lock is write-locked, this function does</span>
<span class="comment">// nothing.</span>
<span class="comment">//</span>
<span class="comment">// If this (the caller's?) lock is read-locked and the next request or consecutive</span>
<span class="comment">// requests in the queue are read requests, those requests will be</span>
<span class="comment">// fulfilled, unparking their respective tasks and incrementing the</span>
<span class="comment">// read-lock count appropriately.</span>
<span class="comment">//</span>
<span class="comment">//</span>
<span class="comment">// TODO:</span>
<span class="comment">// * This is currently public due to 'derivers' (aka. sub-types). Evaluate.</span>
<span class="comment">// * Consider removing unsafe qualifier (should be fine, this fn assumes</span>
<span class="comment">// no particular state).</span>
<span class="comment">// * Return proper error type.</span>
<span class="comment">//</span>
<span class="comment">// pub unsafe fn process_queues(&self) -> Result<(), ()> {</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">process_queues</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Processing queue (thread: {}) ..."</span>,
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">contend</span>() {
<span class="comment">// Unlocked:</span>
<span class="number">0</span> <span class="op">=></span> {
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Processing queue: Unlocked (thread: {}) ..."</span>,
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="kw">let</span> <span class="ident">new_state</span> <span class="op">=</span> <span class="kw">if</span> <span class="self">self</span>.<span class="ident">process_upgrade_queue</span>() {
<span class="ident">WRITE_LOCKED</span>
} <span class="kw">else</span> {
<span class="self">self</span>.<span class="ident">fulfill_request</span>(<span class="number">0</span>)
};
<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">store</span>(<span class="ident">new_state</span>, <span class="ident">SeqCst</span>);
},
<span class="comment">// Write locked, unset CONTENDED flag:</span>
<span class="ident">WRITE_LOCKED</span> <span class="op">=></span> {
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Processing queue: Write Locked (thread: {}) ..."</span>,
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">store</span>(<span class="ident">WRITE_LOCKED</span>, <span class="ident">SeqCst</span>);
},
<span class="comment">// Either read locked or already being processed:</span>
<span class="ident">state</span> <span class="op">=></span> {
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">load</span>(<span class="ident">SeqCst</span>) <span class="op">&</span> <span class="ident">CONTENDED</span> <span class="op">!=</span> <span class="number">0</span>);
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="ident">state</span> <span class="op"><=</span> <span class="ident">READ_COUNT_MASK</span>);
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Processing queue: Other {{ state: {}, peek: {:?} }} \
(thread: {}) ..."</span>, <span class="ident">state</span>, <span class="self">self</span>.<span class="ident">peek_request_kind</span>(),
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">peek_request_kind</span>() <span class="op">==</span> <span class="prelude-val">Some</span>(<span class="ident">RequestKind</span>::<span class="ident">Read</span>) {
<span class="comment">// We are read locked and the next request is a read.</span>
<span class="kw">let</span> <span class="ident">new_state</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">fulfill_request</span>(<span class="ident">state</span>);
<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">store</span>(<span class="ident">new_state</span>, <span class="ident">SeqCst</span>);
} <span class="kw">else</span> {
<span class="comment">// Either the next request is empty or a write and</span>
<span class="comment">// we are already read locked. Leave the request</span>
<span class="comment">// there and restore our original state, removing</span>
<span class="comment">// the CONTENDED flag.</span>
<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">store</span>(<span class="ident">state</span>, <span class="ident">SeqCst</span>);
}
},
}
}
<span class="doccomment">/// Enqueues an upgrade.</span>
<span class="kw">fn</span> <span class="ident">enqueue_upgrade_request</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">state</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="ident">Receiver</span><span class="op"><</span>()<span class="op">></span> {
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="ident">state</span> <span class="op">></span> <span class="number">0</span> <span class="op">&&</span> <span class="ident">state</span> <span class="op">&</span> <span class="ident">CONTENDED</span> <span class="op">==</span> <span class="number">0</span> <span class="op">&&</span> <span class="ident">state</span> <span class="op">&</span> <span class="ident">WRITE_LOCKED</span> <span class="op">==</span> <span class="number">0</span>);
<span class="kw">let</span> (<span class="ident">tx</span>, <span class="ident">rx</span>) <span class="op">=</span> <span class="ident">oneshot</span>::<span class="ident">channel</span>();
<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">upgrade_queue</span>.<span class="ident">push</span>(<span class="ident">tx</span>);
<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">store</span>(<span class="ident">state</span> <span class="op">-</span> <span class="number">1</span>, <span class="ident">SeqCst</span>);
<span class="ident">rx</span>
}
<span class="doccomment">/// Converts a single read lock (read count of '1') into a write lock.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Returns an error containing a oneshot receiver if there is currently</span>
<span class="doccomment">/// more than one read lock. When the read count reaches one, the receiver</span>
<span class="doccomment">/// channel will be completed (i.e. poll it).</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Panics if there are no read locks.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Do not call this method directly unless you are using a custom guard</span>
<span class="doccomment">/// or are otherwise managing the lock state manually. Use</span>
<span class="doccomment">/// `ReadGuard::upgrade` instead.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">upgrade_read_lock</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span>(), <span class="ident">Receiver</span><span class="op"><</span>()<span class="op">>></span> {
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Attempting to upgrade reader to writer: (thread: {}) ..."</span>,
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">contend</span>() {
<span class="number">0</span> <span class="op">=></span> <span class="macro">panic</span><span class="macro">!</span>(<span class="string">"Unable to upgrade this QrwLock: no read locks."</span>),
<span class="ident">WRITE_LOCKED</span> <span class="op">=></span> <span class="macro">panic</span><span class="macro">!</span>(<span class="string">"Unable to upgrade this QrwLock: already write locked."</span>),
<span class="ident">state</span> <span class="op">=></span> {
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">load</span>(<span class="ident">SeqCst</span>) <span class="op">&</span> <span class="ident">CONTENDED</span> <span class="op">!=</span> <span class="number">0</span>);
<span class="macro">debug_assert_eq</span><span class="macro">!</span>(<span class="ident">state</span>, <span class="self">self</span>.<span class="ident">read_count</span>().<span class="ident">unwrap</span>() <span class="kw">as</span> <span class="ident">usize</span>);
<span class="kw">if</span> <span class="ident">state</span> <span class="op">==</span> <span class="number">1</span> {
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">upgrade_queue</span>.<span class="ident">is_empty</span>() {
<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">store</span>(<span class="ident">WRITE_LOCKED</span>, <span class="ident">SeqCst</span>);
<span class="prelude-val">Ok</span>(())
} <span class="kw">else</span> {
<span class="prelude-val">Err</span>(<span class="self">self</span>.<span class="ident">enqueue_upgrade_request</span>(<span class="ident">state</span>))
}
} <span class="kw">else</span> {
<span class="prelude-val">Err</span>(<span class="self">self</span>.<span class="ident">enqueue_upgrade_request</span>(<span class="ident">state</span>))
}
},
}
}
<span class="doccomment">/// Converts a write lock into a read lock then processes the queue,</span>
<span class="doccomment">/// allowing additional read requests to acquire locks.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Use `WriteGuard::downgrade` rather than calling this directly.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">downgrade_write_lock</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Attempting to downgrade write lock...(thread: {}) ..."</span>,
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="macro">debug_assert_eq</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">load</span>(<span class="ident">SeqCst</span>) <span class="op">&</span> <span class="ident">WRITE_LOCKED</span>, <span class="ident">WRITE_LOCKED</span>);
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">contend</span>() {
<span class="number">0</span> <span class="op">=></span> <span class="macro">debug_assert</span><span class="macro">!</span>(<span class="bool-val">false</span>, <span class="string">"unreachable"</span>),
<span class="ident">WRITE_LOCKED</span> <span class="op">=></span> {
<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">store</span>(<span class="number">1</span>, <span class="ident">SeqCst</span>);
},
<span class="ident">_state</span> <span class="op">=></span> <span class="macro">debug_assert</span><span class="macro">!</span>(<span class="bool-val">false</span>, <span class="string">"unreachable"</span>),
}
<span class="comment">// fence(SeqCst);</span>
<span class="self">self</span>.<span class="ident">process_queues</span>();
}
<span class="doccomment">/// Decreases the reader count by one and unparks the next requester task</span>
<span class="doccomment">/// in the queue if possible.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If a reader is waiting to be upgraded and the read lock count reaches</span>
<span class="doccomment">/// 1, the upgrade sender will be completed.</span>
<span class="comment">//</span>
<span class="comment">// TODO: Consider using `Ordering::Release`.</span>
<span class="comment">// TODO: Wire up upgrade checking (if reader count == 1, complete `upgrade_tx`).</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">release_read_lock</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Releasing read lock...(thread: {}) ..."</span>,
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="comment">// Ensure we are read locked and not processing or write locked:</span>
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">load</span>(<span class="ident">SeqCst</span>) <span class="op">&</span> <span class="ident">READ_COUNT_MASK</span> <span class="op">!=</span> <span class="number">0</span>);
<span class="macro">debug_assert_eq</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">load</span>(<span class="ident">SeqCst</span>) <span class="op">&</span> <span class="ident">WRITE_LOCKED</span>, <span class="number">0</span>);
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">contend</span>() {
<span class="number">0</span> <span class="op">=></span> <span class="macro">debug_assert</span><span class="macro">!</span>(<span class="bool-val">false</span>, <span class="string">"unreachable"</span>),
<span class="ident">WRITE_LOCKED</span> <span class="op">=></span> <span class="macro">debug_assert</span><span class="macro">!</span>(<span class="bool-val">false</span>, <span class="string">"unreachable"</span>),
<span class="ident">state</span> <span class="op">=></span> {
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">load</span>(<span class="ident">SeqCst</span>) <span class="op">&</span> <span class="ident">CONTENDED</span> <span class="op">!=</span> <span class="number">0</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">state</span> <span class="op">></span> <span class="number">0</span> <span class="op">&&</span> <span class="ident">state</span> <span class="op"><=</span> <span class="ident">READ_COUNT_MASK</span>);
<span class="kw">let</span> <span class="ident">new_state</span> <span class="op">=</span> <span class="ident">state</span> <span class="op">-</span> <span class="number">1</span>;
<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">store</span>(<span class="ident">new_state</span>, <span class="ident">SeqCst</span>);
<span class="self">self</span>.<span class="ident">process_queues</span>();
}
}
}
<span class="doccomment">/// Unlocks this (the caller's) lock and unparks the next requester task</span>
<span class="doccomment">/// in the queue if possible.</span>
<span class="comment">//</span>
<span class="comment">// TODO: Consider using `Ordering::Release`.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">release_write_lock</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="kw">if</span> <span class="ident">PRINT_DEBUG</span> { <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Releasing write lock...(thread: {}) ..."</span>,
<span class="ident">thread</span>::<span class="ident">current</span>().<span class="ident">name</span>().<span class="ident">unwrap_or</span>(<span class="string">"<unnamed>"</span>)); }
<span class="comment">// If we are not WRITE_LOCKED, we must be CONTENDED (and will soon be</span>
<span class="comment">// write locked).</span>
<span class="macro">debug_assert</span><span class="macro">!</span>({
<span class="kw">let</span> <span class="ident">state</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">load</span>(<span class="ident">SeqCst</span>);
(<span class="ident">state</span> <span class="op">&</span> <span class="ident">CONTENDED</span> <span class="op">==</span> <span class="ident">CONTENDED</span>) <span class="op">==</span> (<span class="ident">state</span> <span class="op">&</span> <span class="ident">WRITE_LOCKED</span> <span class="op">!=</span> <span class="ident">WRITE_LOCKED</span>) <span class="op">||</span>
(<span class="ident">state</span> <span class="op">&</span> <span class="ident">CONTENDED</span> <span class="op">==</span> <span class="ident">CONTENDED</span>) <span class="op">&&</span> (<span class="ident">state</span> <span class="op">&</span> <span class="ident">WRITE_LOCKED</span> <span class="op">==</span> <span class="ident">WRITE_LOCKED</span>)
});
<span class="comment">// Ensure we are not read locked.</span>
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">load</span>(<span class="ident">SeqCst</span>) <span class="op">&</span> <span class="ident">READ_COUNT_MASK</span> <span class="op">==</span> <span class="number">0</span>);
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">contend</span>() {
<span class="number">0</span> <span class="op">=></span> <span class="macro">debug_assert</span><span class="macro">!</span>(<span class="bool-val">false</span>, <span class="string">"unreachable"</span>),
<span class="ident">WRITE_LOCKED</span> <span class="op">=></span> {
<span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">state</span>.<span class="ident">store</span>(<span class="number">0</span>, <span class="ident">SeqCst</span>);
<span class="self">self</span>.<span class="ident">process_queues</span>();
},
<span class="ident">_state</span> <span class="op">=></span> <span class="macro">debug_assert</span><span class="macro">!</span>(<span class="bool-val">false</span>, <span class="string">"unreachable"</span>),
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">From</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">for</span> <span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">from</span>(<span class="ident">val</span>: <span class="ident">T</span>) <span class="op">-></span> <span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">QrwLock</span>::<span class="ident">new</span>(<span class="ident">val</span>)
}
}
<span class="comment">// Avoids needing `T: Clone`.</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Clone</span> <span class="kw">for</span> <span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">clone</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">QrwLock</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">QrwLock</span> {
<span class="ident">inner</span>: <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">clone</span>(),
}
}
}
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span>
<span class="comment">// Woefully incomplete.</span>
<span class="kw">mod</span> <span class="ident">tests</span> {
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">thread</span>;
<span class="kw">use</span> <span class="ident">futures</span>::<span class="ident">future</span>;
<span class="kw">use</span> <span class="kw">super</span>::<span class="kw-2">*</span>;
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">simple</span>() {
<span class="kw">let</span> <span class="ident">lock</span> <span class="op">=</span> <span class="ident">QrwLock</span>::<span class="ident">from</span>(<span class="number">0i32</span>);
<span class="kw">let</span> (<span class="ident">future_r0_a</span>, <span class="ident">future_r0_b</span>) <span class="op">=</span> (<span class="ident">lock</span>.<span class="ident">clone</span>().<span class="ident">read</span>(), <span class="ident">lock</span>.<span class="ident">clone</span>().<span class="ident">read</span>());
<span class="kw">let</span> <span class="ident">future_r0</span> <span class="op">=</span> <span class="ident">Box</span>::<span class="ident">new</span>(<span class="ident">lock</span>.<span class="ident">clone</span>().<span class="ident">read</span>().<span class="ident">and_then</span>(<span class="op">|</span><span class="ident">guard</span><span class="op">|</span> {
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="ident">guard</span>, <span class="number">0</span>);
<span class="macro">println</span><span class="macro">!</span>(<span class="string">"val[r0]: {}"</span>, <span class="kw-2">*</span><span class="ident">guard</span>);
<span class="ident">ReadGuard</span>::<span class="ident">release</span>(<span class="ident">guard</span>);
<span class="ident">future_r0_a</span>.<span class="ident">and_then</span>(<span class="op">|</span><span class="ident">guard</span><span class="op">|</span> {
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="ident">guard</span>, <span class="number">0</span>);
<span class="macro">println</span><span class="macro">!</span>(<span class="string">"val[r0a]: {}"</span>, <span class="kw-2">*</span><span class="ident">guard</span>);
<span class="prelude-val">Ok</span>(())
}).<span class="ident">wait</span>().<span class="ident">unwrap</span>();
<span class="ident">future_r0_b</span>.<span class="ident">and_then</span>(<span class="op">|</span><span class="ident">guard</span><span class="op">|</span> {
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="ident">guard</span>, <span class="number">0</span>);
<span class="macro">println</span><span class="macro">!</span>(<span class="string">"val[r0b]: {}"</span>, <span class="kw-2">*</span><span class="ident">guard</span>);
<span class="prelude-val">Ok</span>(())
}).<span class="ident">wait</span>().<span class="ident">unwrap</span>();
<span class="prelude-val">Ok</span>(())
}));
<span class="kw">let</span> <span class="ident">future_w0</span> <span class="op">=</span> <span class="ident">Box</span>::<span class="ident">new</span>(<span class="ident">lock</span>.<span class="ident">clone</span>().<span class="ident">write</span>().<span class="ident">and_then</span>(<span class="op">|</span><span class="kw-2">mut</span> <span class="ident">guard</span><span class="op">|</span> {
<span class="kw-2">*</span><span class="ident">guard</span> <span class="op">=</span> <span class="number">5</span>;
<span class="macro">println</span><span class="macro">!</span>(<span class="string">"val is now: {}"</span>, <span class="kw-2">*</span><span class="ident">guard</span>);
<span class="prelude-val">Ok</span>(())
}));
<span class="kw">let</span> <span class="ident">future_r1</span> <span class="op">=</span> <span class="ident">Box</span>::<span class="ident">new</span>(<span class="ident">lock</span>.<span class="ident">clone</span>().<span class="ident">read</span>().<span class="ident">and_then</span>(<span class="op">|</span><span class="ident">guard</span><span class="op">|</span> {
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="ident">guard</span>, <span class="number">5</span>);
<span class="macro">println</span><span class="macro">!</span>(<span class="string">"val[r1]: {}"</span>, <span class="kw-2">*</span><span class="ident">guard</span>);
<span class="prelude-val">Ok</span>(())
}));
<span class="kw">let</span> <span class="ident">future_r2</span> <span class="op">=</span> <span class="ident">Box</span>::<span class="ident">new</span>(<span class="ident">lock</span>.<span class="ident">clone</span>().<span class="ident">read</span>().<span class="ident">and_then</span>(<span class="op">|</span><span class="ident">guard</span><span class="op">|</span> {
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="ident">guard</span>, <span class="number">5</span>);
<span class="macro">println</span><span class="macro">!</span>(<span class="string">"val[r2]: {}"</span>, <span class="kw-2">*</span><span class="ident">guard</span>);
<span class="prelude-val">Ok</span>(())
}));
<span class="kw">let</span> <span class="ident">future_u0</span> <span class="op">=</span> <span class="ident">Box</span>::<span class="ident">new</span>(<span class="ident">lock</span>.<span class="ident">clone</span>().<span class="ident">read</span>().<span class="ident">and_then</span>(<span class="op">|</span><span class="ident">read_guard</span><span class="op">|</span> {
<span class="macro">println</span><span class="macro">!</span>(<span class="string">"Upgrading read guard..."</span>);
<span class="ident">ReadGuard</span>::<span class="ident">upgrade</span>(<span class="ident">read_guard</span>).<span class="ident">and_then</span>(<span class="op">|</span><span class="kw-2">mut</span> <span class="ident">write_guard</span><span class="op">|</span> {
<span class="macro">println</span><span class="macro">!</span>(<span class="string">"Read guard upgraded."</span>);
<span class="kw-2">*</span><span class="ident">write_guard</span> <span class="op">=</span> <span class="number">6</span>;
<span class="prelude-val">Ok</span>(())
})
}));
<span class="comment">// This read will take place before the above read lock can be</span>
<span class="comment">// upgraded because read requests are processed in a chained fashion:</span>
<span class="kw">let</span> <span class="ident">future_r3</span> <span class="op">=</span> <span class="ident">Box</span>::<span class="ident">new</span>(<span class="ident">lock</span>.<span class="ident">clone</span>().<span class="ident">read</span>().<span class="ident">and_then</span>(<span class="op">|</span><span class="ident">guard</span><span class="op">|</span> {
<span class="comment">// Value should not yet be affected by the events following the</span>
<span class="comment">// above write guard upgrade.</span>
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="ident">guard</span>, <span class="number">5</span>);
<span class="macro">println</span><span class="macro">!</span>(<span class="string">"val[r3]: {}"</span>, <span class="kw-2">*</span><span class="ident">guard</span>);
<span class="prelude-val">Ok</span>(())
}));
<span class="comment">// future_r0.join4(future_w0, future_r1, future_r2).wait().unwrap();</span>
<span class="kw">let</span> <span class="ident">futures</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">Box</span><span class="op"><</span><span class="ident">Future</span><span class="op"><</span><span class="ident">Item</span><span class="op">=</span>(), <span class="ident">Error</span><span class="op">=</span><span class="ident">Canceled</span><span class="op">>></span><span class="op">></span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>[<span class="ident">future_r0</span>, <span class="ident">future_w0</span>, <span class="ident">future_r1</span>, <span class="ident">future_r2</span>, <span class="ident">future_u0</span>, <span class="ident">future_r3</span>];
<span class="ident">future</span>::<span class="ident">join_all</span>(<span class="ident">futures</span>).<span class="ident">wait</span>().<span class="ident">unwrap</span>();
<span class="kw">let</span> <span class="ident">future_guard</span> <span class="op">=</span> <span class="ident">lock</span>.<span class="ident">clone</span>().<span class="ident">read</span>();
<span class="kw">let</span> <span class="ident">guard</span> <span class="op">=</span> <span class="ident">future_guard</span>.<span class="ident">wait</span>().<span class="ident">unwrap</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="ident">guard</span>, <span class="number">6</span>);
}
<span class="comment">// This doesn't really prove much...</span>
<span class="comment">//</span>
<span class="comment">// * TODO: *Actually* determine whether or not the lock acquisition order is</span>
<span class="comment">// upheld.</span>
<span class="comment">//</span>
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">concurrent</span>() {
<span class="kw">let</span> <span class="ident">start_val</span> <span class="op">=</span> <span class="number">0i32</span>;
<span class="kw">let</span> <span class="ident">lock</span> <span class="op">=</span> <span class="ident">QrwLock</span>::<span class="ident">new</span>(<span class="ident">start_val</span>);
<span class="kw">let</span> <span class="ident">thread_count</span> <span class="op">=</span> <span class="number">20</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">threads</span> <span class="op">=</span> <span class="ident">Vec</span>::<span class="ident">with_capacity</span>(<span class="ident">thread_count</span>);
<span class="kw">for</span> <span class="ident">_i</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">thread_count</span> {
<span class="kw">let</span> <span class="ident">future_write_guard</span> <span class="op">=</span> <span class="ident">lock</span>.<span class="ident">clone</span>().<span class="ident">write</span>();
<span class="kw">let</span> <span class="ident">future_read_guard</span> <span class="op">=</span> <span class="ident">lock</span>.<span class="ident">clone</span>().<span class="ident">read</span>();
<span class="kw">let</span> <span class="ident">future_write</span> <span class="op">=</span> <span class="ident">future_write_guard</span>.<span class="ident">and_then</span>(<span class="op">|</span><span class="kw-2">mut</span> <span class="ident">guard</span><span class="op">|</span> {
<span class="kw-2">*</span><span class="ident">guard</span> <span class="op">+=</span> <span class="number">1</span>;
<span class="ident">WriteGuard</span>::<span class="ident">downgrade</span>(<span class="ident">guard</span>);
<span class="prelude-val">Ok</span>(())
});
<span class="kw">let</span> <span class="ident">future_read</span> <span class="op">=</span> <span class="ident">future_read_guard</span>.<span class="ident">and_then</span>(<span class="kw">move</span> <span class="op">|</span><span class="ident">guard</span><span class="op">|</span> {
<span class="comment">// println!("Value for thread '{}' is: {}", _i, *_guard);</span>
<span class="prelude-val">Ok</span>(<span class="ident">guard</span>)
});
<span class="ident">threads</span>.<span class="ident">push</span>(<span class="ident">thread</span>::<span class="ident">spawn</span>(<span class="op">||</span> {
<span class="ident">future_write</span>.<span class="ident">join</span>(<span class="ident">future_read</span>).<span class="ident">wait</span>().<span class="ident">unwrap</span>();
}));
}
<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">thread_count</span> {
<span class="kw">let</span> <span class="ident">future_write_guard</span> <span class="op">=</span> <span class="ident">lock</span>.<span class="ident">clone</span>().<span class="ident">write</span>();
<span class="ident">threads</span>.<span class="ident">push</span>(<span class="ident">thread</span>::<span class="ident">Builder</span>::<span class="ident">new</span>().<span class="ident">name</span>(<span class="macro">format</span><span class="macro">!</span>(<span class="string">"test_thread_{}"</span>, <span class="ident">i</span>)).<span class="ident">spawn</span>(<span class="op">||</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">guard</span> <span class="op">=</span> <span class="ident">future_write_guard</span>.<span class="ident">wait</span>().<span class="ident">unwrap</span>();
<span class="kw-2">*</span><span class="ident">guard</span> <span class="op">-=</span> <span class="number">1</span>
}).<span class="ident">unwrap</span>());
<span class="kw">let</span> <span class="ident">future_read_guard</span> <span class="op">=</span> <span class="ident">lock</span>.<span class="ident">clone</span>().<span class="ident">read</span>();
<span class="ident">threads</span>.<span class="ident">push</span>(<span class="ident">thread</span>::<span class="ident">Builder</span>::<span class="ident">new</span>().<span class="ident">name</span>(<span class="macro">format</span><span class="macro">!</span>(<span class="string">"test_thread_{}"</span>, <span class="ident">i</span>)).<span class="ident">spawn</span>(<span class="op">||</span> {
<span class="kw">let</span> <span class="ident">_val</span> <span class="op">=</span> <span class="kw-2">*</span><span class="ident">future_read_guard</span>.<span class="ident">wait</span>().<span class="ident">unwrap</span>();
}).<span class="ident">unwrap</span>());
}
<span class="kw">for</span> <span class="ident">thread</span> <span class="kw">in</span> <span class="ident">threads</span> {
<span class="ident">thread</span>.<span class="ident">join</span>().<span class="ident">unwrap</span>();
}
<span class="kw">let</span> <span class="ident">guard</span> <span class="op">=</span> <span class="ident">lock</span>.<span class="ident">clone</span>().<span class="ident">read</span>().<span class="ident">wait</span>().<span class="ident">unwrap</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="ident">guard</span>, <span class="ident">start_val</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">read_write_thread_loop</span>() {
<span class="kw">let</span> <span class="ident">lock</span> <span class="op">=</span> <span class="ident">QrwLock</span>::<span class="ident">new</span>(<span class="macro">vec</span><span class="macro">!</span>[<span class="number">0usize</span>; <span class="number">1</span> <span class="op"><<</span> <span class="number">13</span>]);
<span class="kw">let</span> <span class="ident">loop_count</span> <span class="op">=</span> <span class="number">15</span>;
<span class="kw">let</span> <span class="ident">redundancy_count</span> <span class="op">=</span> <span class="number">700</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">threads</span> <span class="op">=</span> <span class="ident">Vec</span>::<span class="ident">with_capacity</span>(<span class="ident">loop_count</span> <span class="op">*</span> <span class="number">2</span>);
<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">loop_count</span> {
<span class="kw">let</span> <span class="ident">future_write_guard</span> <span class="op">=</span> <span class="ident">lock</span>.<span class="ident">clone</span>().<span class="ident">write</span>();
<span class="kw">let</span> <span class="ident">future_read_guard</span> <span class="op">=</span> <span class="ident">lock</span>.<span class="ident">clone</span>().<span class="ident">read</span>();
<span class="ident">threads</span>.<span class="ident">push</span>(<span class="ident">thread</span>::<span class="ident">Builder</span>::<span class="ident">new</span>().<span class="ident">name</span>(<span class="macro">format</span><span class="macro">!</span>(<span class="string">"write_thread_{}"</span>, <span class="ident">i</span>)).<span class="ident">spawn</span>(<span class="kw">move</span> <span class="op">||</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">guard</span> <span class="op">=</span> <span class="ident">future_write_guard</span>.<span class="ident">wait</span>().<span class="ident">unwrap</span>();
<span class="kw">for</span> _ <span class="kw">in</span> <span class="number">0</span>..<span class="ident">redundancy_count</span> {
<span class="kw">for</span> <span class="ident">idx</span> <span class="kw">in</span> <span class="ident">guard</span>.<span class="ident">iter_mut</span>() {
<span class="kw-2">*</span><span class="ident">idx</span> <span class="op">+=</span> <span class="number">1</span>;
}
}
}).<span class="ident">unwrap</span>());
<span class="ident">threads</span>.<span class="ident">push</span>(<span class="ident">thread</span>::<span class="ident">Builder</span>::<span class="ident">new</span>().<span class="ident">name</span>(<span class="macro">format</span><span class="macro">!</span>(<span class="string">"read_thread_{}"</span>, <span class="ident">i</span>)).<span class="ident">spawn</span>(<span class="kw">move</span> <span class="op">||</span> {
<span class="kw">let</span> <span class="ident">guard</span> <span class="op">=</span> <span class="ident">future_read_guard</span>.<span class="ident">wait</span>().<span class="ident">unwrap</span>();
<span class="kw">let</span> <span class="ident">expected_val</span> <span class="op">=</span> <span class="ident">redundancy_count</span> <span class="op">*</span> (<span class="ident">i</span> <span class="op">+</span> <span class="number">1</span>);
<span class="kw">for</span> <span class="ident">idx</span> <span class="kw">in</span> <span class="ident">guard</span>.<span class="ident">iter</span>() {
<span class="macro">assert</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="ident">idx</span> <span class="op">==</span> <span class="ident">expected_val</span>, <span class="string">"Lock data mismatch. \
{} expected, {} found."</span>, <span class="ident">expected_val</span>, <span class="kw-2">*</span><span class="ident">idx</span>);
}
}).<span class="ident">unwrap</span>());
}
<span class="kw">for</span> <span class="ident">thread</span> <span class="kw">in</span> <span class="ident">threads</span> {
<span class="ident">thread</span>.<span class="ident">join</span>().<span class="ident">unwrap</span>();
}
<span class="kw">let</span> <span class="ident">guard</span> <span class="op">=</span> <span class="ident">lock</span>.<span class="ident">clone</span>().<span class="ident">read</span>().<span class="ident">wait</span>().<span class="ident">unwrap</span>();
<span class="kw">for</span> <span class="ident">idx</span> <span class="kw">in</span> <span class="ident">guard</span>.<span class="ident">iter</span>() {
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="ident">idx</span>, <span class="ident">loop_count</span> <span class="op">*</span> <span class="ident">redundancy_count</span>);
}
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">multiple_upgrades</span>() {
<span class="kw">let</span> <span class="ident">lock</span> <span class="op">=</span> <span class="ident">QrwLock</span>::<span class="ident">new</span>(<span class="number">0usize</span>);
<span class="kw">let</span> <span class="ident">upgrade_count</span> <span class="op">=</span> <span class="number">12</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">threads</span> <span class="op">=</span> <span class="ident">Vec</span>::<span class="ident">with_capacity</span>(<span class="ident">upgrade_count</span> <span class="op">*</span> <span class="number">2</span>);
<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">upgrade_count</span> {
<span class="kw">let</span> <span class="ident">future_read_guard_a</span> <span class="op">=</span> <span class="ident">lock</span>.<span class="ident">clone</span>().<span class="ident">read</span>();
<span class="kw">let</span> <span class="ident">future_read_guard_b</span> <span class="op">=</span> <span class="ident">lock</span>.<span class="ident">clone</span>().<span class="ident">read</span>();
<span class="ident">threads</span>.<span class="ident">push</span>(<span class="ident">thread</span>::<span class="ident">Builder</span>::<span class="ident">new</span>().<span class="ident">name</span>(<span class="macro">format</span><span class="macro">!</span>(<span class="string">"read_thread_{}"</span>, <span class="ident">i</span>)).<span class="ident">spawn</span>(<span class="kw">move</span> <span class="op">||</span> {
<span class="kw">let</span> <span class="ident">_read_guard</span> <span class="op">=</span> <span class="ident">future_read_guard_a</span>.<span class="ident">wait</span>().<span class="ident">expect</span>(<span class="string">"[0]"</span>);
::<span class="ident">std</span>::<span class="ident">thread</span>::<span class="ident">sleep</span>(::<span class="ident">std</span>::<span class="ident">time</span>::<span class="ident">Duration</span>::<span class="ident">from_millis</span>(<span class="number">500</span>));
}).<span class="ident">expect</span>(<span class="string">"[1]"</span>));
<span class="ident">threads</span>.<span class="ident">push</span>(<span class="ident">thread</span>::<span class="ident">Builder</span>::<span class="ident">new</span>().<span class="ident">name</span>(<span class="macro">format</span><span class="macro">!</span>(<span class="string">"upgrade_thread_{}"</span>, <span class="ident">i</span>)).<span class="ident">spawn</span>(<span class="kw">move</span> <span class="op">||</span> {
<span class="kw">let</span> <span class="ident">read_guard</span> <span class="op">=</span> <span class="ident">future_read_guard_b</span>.<span class="ident">wait</span>().<span class="ident">expect</span>(<span class="string">"[2]"</span>);
<span class="kw">let</span> <span class="ident">upgrade_guard</span> <span class="op">=</span> <span class="ident">ReadGuard</span>::<span class="ident">upgrade</span>(<span class="ident">read_guard</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">write_guard</span> <span class="op">=</span> <span class="ident">upgrade_guard</span>.<span class="ident">wait</span>().<span class="ident">expect</span>(<span class="string">"Error waiting for upgrade guard"</span>);
<span class="kw-2">*</span><span class="ident">write_guard</span> <span class="op">+=</span> <span class="number">1</span>;
}).<span class="ident">expect</span>(<span class="string">"[4]"</span>));
}
<span class="kw">for</span> <span class="ident">handle</span> <span class="kw">in</span> <span class="ident">threads</span> {
<span class="kw">let</span> <span class="ident">name</span> <span class="op">=</span> <span class="ident">handle</span>.<span class="ident">thread</span>().<span class="ident">name</span>().<span class="ident">unwrap</span>().<span class="ident">to_owned</span>();
<span class="ident">handle</span>.<span class="ident">join</span>().<span class="ident">expect</span>(<span class="kw-2">&</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">"Error joining thread: {:?}"</span>, <span class="ident">name</span>));
}
<span class="kw">let</span> <span class="ident">guard</span> <span class="op">=</span> <span class="ident">lock</span>.<span class="ident">read</span>().<span class="ident">wait</span>().<span class="ident">expect</span>(<span class="string">"[6]"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">*</span><span class="ident">guard</span>, <span class="ident">upgrade_count</span>);
}
}</pre>
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