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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [linux] I/O over pty arrives asynchronously, which confuses LLDB"
href="https://llvm.org/bugs/show_bug.cgi?id=25652">25652</a>
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<th>Summary</th>
<td>[linux] I/O over pty arrives asynchronously, which confuses LLDB
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<th>Product</th>
<td>lldb
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>All Bugs
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<th>Assignee</th>
<td>lldb-dev@lists.llvm.org
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<th>Reporter</th>
<td>labath@google.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>According to this <<a href="https://lkml.org/lkml/2015/11/3/795">https://lkml.org/lkml/2015/11/3/795</a>> discussion, there is
basically no guarantee about when will I/O from the inferior process arrive.
Specifically, it can arrive after we have it has stopped and we think we have
forwarded all of its input. This can cause two problems:
- the test suite sometimes checks the output of the process to verify it has
done the right thing. The late arrival of this text can cause flakyness.
- gdb-remote protocol does not support forwarding I/O when the process is
stopped. Currently, we will still attempt to do that and then things will
break.
The possible fixes for this would be: patching the kernel (which is a
possibility they seemed opened (or at least not opposed) to), inserting sleeps
or stopping using stdio in tests.
Although it is possible to reliably reproduce it with a specially crafted
program, I have seen this happen on the buildbot only once. Given that this
does not seem to happen very often, it does not seem like a big priority.
However, we should do something about the protocol forwarding issue, because
when this happens, and we are forwarding I/O, the entire debug session will
break down, which is not good.</pre>
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