<html>
<head>
<base href="https://bugs.llvm.org/">
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_CONFIRMED "
title="CONFIRMED - std::binary_semaphore::try_acquire() blocks forever"
href="https://bugs.llvm.org/show_bug.cgi?id=49721">49721</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>std::binary_semaphore::try_acquire() blocks forever
</td>
</tr>
<tr>
<th>Product</th>
<td>libc++
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>All
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</td>
</tr>
<tr>
<th>Status</th>
<td>CONFIRMED
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>All Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>raul@tambre.ee
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=24693" name="attach_24693" title="repro">attachment 24693</a> <a href="attachment.cgi?id=24693&action=edit" title="repro">[details]</a></span>
repro
[thread.sema.cnt] says for try_acquire():
Effects: Attempts to atomically decrement counter if it is positive, without
blocking. [...]
libc++'s try_acquire() maps to
try_acquire_for(std::chrono::nanoseconds::zero()) which in the case of
std::binary_semaphore boils down to __libcpp_thread_poll_with_backoff(), which
treats a zero timeout as an infinite timeout, resulting in try_acquire()
blocking forever if it's unable to decrement.
The attached .cpp file demonstrates the problem.</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>