Slightly changed patch:

nvptx_attach_host_thread_to_device now fails again with an error for 
CUDA_ERROR_DEINITIALIZED, except for GOMP_OFFLOAD_fini_device.

I think it makes more sense that way.

Tobias Burnus wrote:
> Testing showed that the libgomp.c/target-52.c failed with:
>
> libgomp: cuCtxGetDevice error: unknown cuda error
>
> libgomp: device finalization failed
>
> This testcase uses OMP_DISPLAY_ENV=true and 
> OMP_TARGET_OFFLOAD=mandatory, and those env vars matter, i.e. it only 
> fails if dg-set-target-env-var is honored.
>
> If both env vars are set, the device initialization occurs earlier as 
> OMP_DEFAULT_DEVICE is shown due to the display-env env var and its 
> value (when target-offload-var is 'mandatory') might be either 
> 'omp_invalid_device' or '0'.
>
> It turned out that this had an effect on device finalization, which 
> caused CUDA to stop earlier than expected. This patch now handles this 
> case gracefully. For details, see the commit log message in the 
> attached patch and/or the PR.
>
> Comments, remarks, suggestions?
>
> Does this look sensible? (I would like to see some acknowledgement by 
> someone who feels more comfortable with CUDA than me.)

Tobias