Bug 30457

Summary:	[7.9] DRI drawables prematurely destroyed on context switch
Product:	Mesa	Reporter:	Christopher James Halse Rogers <chalserogers>
Component:	Mesa core	Assignee:	mesa-dev
Status:	RESOLVED FIXED	QA Contact:
Severity:	normal
Priority:	medium	CC:	sarvatt
Version:	git
Hardware:	Other
OS:	All
Whiteboard:
i915 platform:		i915 features:
Attachments:	Simpleminded patch which fixes Clutter apps.

Description Christopher James Halse Rogers 2010-09-29 04:14:54 UTC

Created attachment 39044 [details] [review]
Simpleminded patch which fixes Clutter apps.

It seems that with the new GLX drawable garbage collection that mesa incorrectly destroys drawables when switching a single context between drawables.

This manifests in some clutter applications crashing with a BadDrawable error:
(quadrapassel:4883): ClutterGLX-CRITICAL **: Unable to make the stage window 0x4800005 the current GLX drawable

(quadrapassel:4883): ClutterGLX-CRITICAL **: Unable to make the stage window 0x4800006 the current GLX drawable

(quadrapassel:4883): ClutterGLX-CRITICAL **: Unable to make the stage window 0x4800006 the current GLX drawable
The program 'quadrapassel' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadDrawable (invalid Pixmap or Window parameter)'.
  (Details: serial 70 error_code 9 request_code 137 minor_code 12)
  (Note to programmers: normally, X errors are reported asynchronously;
   that is, you will receive the error a while after causing it.
   To debug your program, run it with the --sync command line
   option to change this behavior. You can then get a meaningful
   backtrace from your debugger if you break on the gdk_x_error() function.)

The cause is that when dri2_unbind_context is called with new context == old context it calls driReleaseDrawable.  Clutter will switch a single context between different drawables with glXMakeCurrent, so it hits this codepath.  When it switches back to the original drawable, mesa only has the GLXDrawable id which doesn't match the X drawable ID, and hence calls using it result in BadDrawable in clutter.

I've sent a piglit testcase to the piglit list exhibiting this bug.

The attached patch fixes this, but probably leaks drawables.

Comment 1 Kristian Høgsberg 2010-09-29 06:12:56 UTC

4b70fe8421f5132c585ff1dfb8d90229be26e71f should fix the clutter issue, but the piglit test you sent tests something different.  If you look at the actual X errors, the clutter problem comes from glXMakeCurrent getting a BadDrawable, the test case fails in glXSwapBuffers.  To test the clutter problem you'll have to create two GLXDrawables (A and B) and then make a context current with A, then B, then switch back to A.  If you have time to write up a test case for this, that would be much appreciated.

The swapbuffer problem is still present, and I've committed the test case to piglit, but it's a much rarer case to hit.  Few applications do glXSwapBuffer for a drawable that's not also current, but it has to work, of course.

The clutter problem is fixed (reproduced using test-multistage) and cherry-picked back to 7.9 (b24238c49abf9b6aaaac56ffbf45a3c203c7ddd2) so I'll close this bug.

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