Bug 52930

Summary:	glXWaitX is often ineffective
Product:	Mesa	Reporter:	Karl Tomlinson <bugs.freedesktop>
Component:	GLX	Assignee:	mesa-dev
Status:	RESOLVED MOVED	QA Contact:
Severity:	normal
Priority:	medium
Version:	8.0
Hardware:	Other
OS:	All
Whiteboard:
i915 platform:		i915 features:

Description Karl Tomlinson 2012-07-30 01:03:55 UTC

The description of glXWaitX says "X rendering calls made prior to glXWaitX are
guaranteed to be executed before GL rendering calls made after glXWaitX", but
glXWaitX is currently a no-op when direct rendering unless the current
drawable is a window and single buffered.  In situations where
dri2_copy_drawable is used it performs the required X server round trip.

At one point in history glXWaitX called XSync with direct rendering:
http://cgit.freedesktop.org/mesa/mesa/commit/src/glx/x11?id=63b51b5cf17ddde09b72a2811296f37b9a4c5ad2

It seems XSync should be used when dri2_copy_drawable is not necessary.
There is some discussion in this thread:
http://lists.freedesktop.org/archives/mesa-dev/2011-June/008124.html

Perhaps LastKnownRequestProcessed NextRequest can be used to determine whether
the XSync is necessary.  They could also detect that the XSync is not necessary after dri2_copy_drawable.

glxWaitGL looks like a no-op in similar situations.
I wonder whether at least a glFlush is required here.

applegl and indirect contexts appear to support glXWaitX/GL.

Comment 1 GitLab Migration User 2019-09-18 17:44:18 UTC

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