nvglxfix

What's this

A possible fix for the random nvidia linux driver hangs on X. Might also be related to ValveSoftware/gamescope#1592 (NV 4924590) .

It fixes a race condition in nvidia's GLX implementation (libGLX_nvidia.so) that may cause the application's rendering to freeze. It may not effect all hardware / software combinations.

Using it

Just add the library to LD_PRELOAD, something like this:

LD_PRELOAD="/path/to/libnvglxfix.so ${LD_PRELOAD}" my_application

Note that it should be first in the preload chain, as otherwise something else might resolve the real dlsym before we load, making our attempt at hooking it fail. (This is usually the case with wine / proton).

Reproducing the bug

The race involves an XSyncFence reset request from the X client and a "damage trigger" event coming from the nvidia driver. You can help the "damage trigger" event win the race by spamming the X server with requests, causing the client's rendering to lock up.

To reliably reproduce the bug (given that your hardware / software combination is affected):

1. launch the built xspam executable (./xspam) to start spamming the X server with requests.
2. launch an application on the nvidia GPU that's prone to locking up (for example a game using DXVK) without using the fix.
3. observe the application almost instantly freezing.

You may now also try step 2., but try using the fix.

Building

make

or

mkdir build && cd build
cmake .. && make