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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Wayland lacks cross-process synchronisation"
href="https://bugs.freedesktop.org/show_bug.cgi?id=97353">97353</a>
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<th>Summary</th>
<td>Wayland lacks cross-process synchronisation
</td>
</tr>
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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>Other
</td>
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<th>OS</th>
<td>All
</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>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>tomek.bury@gmail.com
</td>
</tr></table>
<p>
<div>
<pre>Currently Wayland synchronisation model is build around an undefined behaviour,
which happens to work correctly with FOSS driver, but isn't guaranteed by
GL/EGL specifications. In other words a perfectly valid GL/EGL driver may not
work with Wayland.
The GL/EGL guarantees read-write synchronisation within a single context and
provides tools to synchronise multiple contexts within a single process, but
there are no guarantees or methods of achieving cross-process synchronisation,
except for Android fences, but those are Android-specific.
The only spec-compliant solution at the moment would be blocking CPU on the
compositor side (eglWaitClient() or glFinish()) before a buffer release event
is sent to the client. Alternatively, Wayland could create and mandate and
extension similar to EGL_ANDROID_native_fence_sync, where EGLSyncKHR objects
can be created from and converted to cross-process integer descriptors, that
are easy to send between client and compositor over Wayland protocol.
<a href="https://www.khronos.org/registry/egl/extensions/ANDROID/EGL_ANDROID_native_fence_sync.txt">https://www.khronos.org/registry/egl/extensions/ANDROID/EGL_ANDROID_native_fence_sync.txt</a>
Basing Wayland on an unspecified behaviour, where implementation detail of one
specific driver happens do deliver a desired result causes grief to other
driver maintainers where such behaviour isn't easy to achieve and, limits
Wayland adoption.</pre>
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