rr stopped working with chromium (or vice versa, as you prefer)

[petermayo]

As a side effect of the following change:
https://codereview.chromium.org/2569413002

chromium under rr on linux stopped showing contents and started just displaying a blue field less a rectangle in each corner.

The change referenced was submitted 2016-12-14 20:42:54 UTC. It changes the handling of GPU support under single process mode (very useful for debugging with rr or gdb).

I suspect chromium is now using some calls that aren't supported in rr.

rr version 4.4.0, Ubuntu 14.04.1

I haven't built rr from source to check that this hasn't been fixed already (yet)

[khuey]

Hmm. I can look at this tomorrow.

[petermayo]

I have built a new rr from source (Interesting I had to push on it a little and use clang-3.5 to get it to compile on my system)

It behaves the same way.

If there is something else I can answer to help, feel free to ask.

[petermayo]

FYI passing --use-gl=osmesa is also a solution.

It would still be useful to identify whether the gap is supportable for the future.

[rocallahan]

rr has some hacks to try to automatically force CPU GL rendering. In particular we block attempts to open certain known DRI devices, and set LIBGL_ALWAYS_SOFTWARE=1. Apparently the latter has stopped working for some reason...

[rocallahan]

(Actually making rr work with the GPU by monitoring driver ioctls might be possible, but it would be a hard project and might end up not being possible at all.)

[khuey]

This works for me with both 4.4.0 and tip (6ba6c33) rr, with Chromium commit a86d0169243b.

According to chrome's about:gpu my driver is Mesa 11.2. Is @petermayo's something different? We might need to add some other sort of suppression a la LIBGL_ALWAYS_SOFTWARE=1 for a different driver.

[petermayo]

@petermayo's is NVIDIA 367.57 without rr, and with rr.

Interesting to read from a blue screen, but luckily dialogs like 'save as HTML' are not affected.

--use-gl=osmesa does indeed seem to yield previous behavior - using the Mesa driver.

[khuey]

If there are environment variables or similar we can set globally that will force Chromium to use osmesa we'd be happy to set them.

[khuey]

Or perhaps some NVIDIA driver file we can hide from the tracee.