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StephanP
09-12-2016, 02:46 AM
Hello,

i recently upgraded my sytem to Ubuntu 16.04. Since there is no fglrx driver for my AMD gpus, i had to use the radeon driver.

My application runs two windows on two gpus (each within its own thread). I used GLFW. The application crashes when the second window tries to swap buffers. If I comment out the second swapbuffers call, everything runs at least.

I tried with a much simpler test program, having two windows on the same gpu, with the same results.


Maybe anyone here has encountered a similar problem and can suggest a workaround.

Thanks in advance.

Silence
09-12-2016, 03:56 AM
How do you ensure each of your contexts are dedicated to different GPUs ? Couldn't it be a bug with glfw or your application ? Did you try another OpenGL windowing library ? What's happening if you use Mesa (software renderer) ?

Also, in order (probably) someone will be able to help you, I highly suggest you to give more information:

What GPUs ?
What windowing layer (XF86 ? Xorg ? wayland maybe) ? Which versions ?
What kernel version ?
There is no fglrx driver for your GPU because (I suppose because your GPU is old) ?

StephanP
09-12-2016, 07:36 AM
There is no fglrx driver, beacuse it is no longer supported and does not exist under Ubuntu 16.04. With 14.04 the application was working well. I can ensure each context is on its own gpu, cause i explicitely define the DISPLAY variable for each thread, and of course the output is only generated on the displays attached to the respective card. On the other hand the error does not appear on 16.04 with one nvidia gpu and two rendering contexts. Bugs are possible but not likely, its just the glfwSwapBuffers of the second window giving a "x error of failed request badmatch (invalid parameter attributes)".

The GPUs are Radeon HD 7870.
Kernel is 4.4.0-36-generic. X.Org X Server 1.18.3 (the latest releases i guess)

Silence
09-12-2016, 08:19 AM
From here (https://help.ubuntu.com/community/RadeonDriver), it looks like your graphic card should be well supported but with the free radeon drivers. On the same page, there's a little description on how to install them.

StephanP
09-12-2016, 08:44 AM
Yes, the radeon driver was installed with the release upgrade. The point is, that is does not work as well as fglrx did on 14.04...

Silence
09-13-2016, 01:39 PM
Yes, the radeon driver was installed with the release upgrade. The point is, that is does not work as well as fglrx did on 14.04...

These are free drivers...
Unfortunately on Linux, nVidia only ruled and still rules. ATI made some quite good drivers (these fglrx) years ago (even if tricky to install), that respect the OpenGL standards more than nVidia. Intel has a lot of free drivers too now but they could be somewhat limited, or making OpenGL tricky to use when you expect good performances.
For going back to AMD, you'll have to stuck with an old distribution if you want to keep fglrx (what I do) or use a more recent hardwares...

The good point with free drivers is that you can report your bugs more easily than with AMD, where they did absolutely not care at all about Linux user requests (at least from what I had to deal with them). So, explaining in detail your issues or even better if you have time, start to debug in order to spot where the issue is, will help them to fix the things. A good starting point might be here (https://bugs.freedesktop.org/describecomponents.cgi?product=Mesa).