[Slackbuilds-users] nvidia-driver CUDA glitch

King Beowulf kingbeowulf at gmail.com
Sun Jul 13 18:18:32 UTC 2014

I just realized a fix for a glitch with the new nvidia-driver and CUDA
initialization.  Since the slackbuild is already in "approved" and its
not fatal unless you run CUDA/OpenCL programs, I'll fix this up on the
next update.  This issue popped up somewhere in the 331.xx drivers.

For those of you, as I do, who run BOINC, or another CUDA program, you
may have wondered about "no usable GPUs found" message in the BOINC log.
 Turns out, some weird process in the way Nvidia does things now, since
the introduction of nvidia-uvm.ko, prevents the creation of a required
device node unless you first run your CUDA program as "root."  This then
creates the device node and all is then well as a regular user.  You
should see:

$ ls -l /dev/nvidia-uvm
crw-rw-rw- 1 root root 248, 0 Jul 13 01:45 /dev/nvidia-uvm

A quick test program, as well as possible fixes, are in the Reference
below. The question now is, how best to handle this in the slackbuild?

1. put this in doinst.sh
    mknod -m 660 /dev/nvidia-uvm c 249 0
    chgrp video /dev/nvidia-uvm

2. udev rule?
    KERNEL=="nvidia_uvm", RUN+="/usr/bin/bash -c '/usr/bin/mknod -m 666
/dev/nvidia-uvm c $(grep nvidia-uvm /proc/devices | cut -d \ -f 1) 0;
/usr/bin/chgrp video /dev/nvidia-uvm'"

3. Compile nvidia-modprobe by default (optional now) so that X userland
can make the node, or invoke via doinst.sh if not.

I'll post this in LQ as well to get better coverage.


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