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<base href="https://bugs.freedesktop.org/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - It's not safe to share wl_display fd with other threads."
href="https://bugs.freedesktop.org/show_bug.cgi?id=91273">91273</a>
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<th>Summary</th>
<td>It's not safe to share wl_display fd with other threads.
</td>
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<th>Product</th>
<td>Wayland
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>All
</td>
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<th>OS</th>
<td>All
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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>medium
</td>
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<th>Component</th>
<td>wayland
</td>
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<th>Assignee</th>
<td>wayland-bugs@lists.freedesktop.org
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<th>Reporter</th>
<td>boram1288@gmail.com
</td>
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<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=117010" name="attach_117010" title="simple test application to reproduce this bug">attachment 117010</a> <a href="attachment.cgi?id=117010&action=edit" title="simple test application to reproduce this bug">[details]</a></span>
simple test application to reproduce this bug
Condition:
2 threads polling on same display fd in both threads.
Result:
When one thread awakes, if it quickly reads all events from display fd before
kernel wakes up another, then another can't awake from poll(). I attached a
very simple test application to reproduce this.
Real example:
gstreamer's waylandsink can do polling on same diplay fd of toolkit's
main-thread(Such like GTK and EFL...).
(<a href="http://cgit.freedesktop.org/gstreamer/gst-plugins-bad/tree/ext/wayland/wldisplay.c">http://cgit.freedesktop.org/gstreamer/gst-plugins-bad/tree/ext/wayland/wldisplay.c</a>)
If waylandsink's thread reads all event using wl_display_read_events before
toolkit's main-thread awakes, although all events are queued into corresponding
event queues, default queue's events can't be handled because main-thread is
still sleeping.
Comment:
poll(), select()... seems not guarantee that kernel will wake all threads up
when events happen. Creating new queue seems a good solution if we want to
handle events of a certain wl_proxy. But not in this case. Maybe using a
different display fd will be a good solution. But for using a different display
fd, we have to create new display, then waylandsink can't use parent surface
and create subsurface. Or else, can it be solution creating new fd for each
queue?</pre>
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