[Bug 110706] glFinish does not wait for VBlank

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=110706

            Bug ID: 110706
           Summary: glFinish does not wait for VBlank
           Product: Mesa
           Version: 19.0
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: major
          Priority: medium
         Component: Drivers/DRI/i965
          Assignee: intel-3d-bugs at lists.freedesktop.org
          Reporter: acc12345acc at gmail.com
        QA Contact: intel-3d-bugs at lists.freedesktop.org

Created attachment 144297
  --> https://bugs.freedesktop.org/attachment.cgi?id=144297&action=edit
triangle test

I have attached a test program (compile with `g++ -o triangle triangle.cpp -lGL
-lGLEW -lglfw`).

The triangle must rotate for 0.5 seconds, then stop for 0.5 seconds and
continue rotating for 0.5 seconds, then stop for 0.5 seconds and so on. If this
is the case, then it means glFinish is working correctly and waiting for
VBlank. (indicated by "PASSED" after 5 seconds)

However, under Intel, the triangle does not continue rotating after stopping,
but rather it skips, which means glFinish is not waiting and Mesa is catching
up. (indicated by "FAILED")

Setting LIBGL_DRI3_DISABLE=1 works around the problem, but it isn't a solution.

glxinfo | grep OpenGL:

```
OpenGL vendor string: Intel Open Source Technology Center
OpenGL renderer string: Mesa DRI Intel(R) Ivybridge Mobile 
OpenGL core profile version string: 4.2 (Core Profile) Mesa 19.0.4
OpenGL core profile shading language version string: 4.20
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile
OpenGL core profile extensions:
OpenGL version string: 3.0 Mesa 19.0.4
OpenGL shading language version string: 1.30
OpenGL context flags: (none)
OpenGL extensions:
OpenGL ES profile version string: OpenGL ES 3.0 Mesa 19.0.4
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.00
OpenGL ES profile extensions:
```
uname -a:
```
Linux work 5.0.7-arch1-1-ARCH #1 SMP PREEMPT Mon Apr 8 10:37:08 UTC 2019 x86_64
GNU/Linux
```

/etc/os-release:
```
NAME="Arch Linux"
PRETTY_NAME="Arch Linux"
ID=arch
BUILD_ID=rolling
ANSI_COLOR="0;36"
HOME_URL="https://www.archlinux.org/"
DOCUMENTATION_URL="https://wiki.archlinux.org/"
SUPPORT_URL="https://bbs.archlinux.org/"
BUG_REPORT_URL="https://bugs.archlinux.org/"
```

lscpu model name: Intel(R) Core(TM) i5-3210M CPU @ 2.50GHz
DRI version: 3

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