debugging - cuda infinite kernel

Question

I am working on an application for which it is necessary to run a CUDA kernel indefinitely. I have one CPU thread that writes stg on a list and gpu reads that list and resets (at least for start). When I write inside the kernel

while(true)
{
//kernel code
}

the system hangs up. I know that the GPU is still processing but nothing happens of course. And I am not sure that the reset at the list happens.

I have to mention that the GPU used for calculations is not used for display, so no watchdog problem.

The OS is Ubuntu 11.10 and cuda toolkit 4.1. I could use any help/examples/links on writing infinite kernel successfully.

Answer 1

The CUDA programming language and the CUDA architecture do not currently support infinite kernels. I suggest you consider Roger's suggestion.

If you want to pursue this I suggest you add the following debug code to your kernel:

1. Increment a variable in pinned memory every N clocks (may want a different location for each SM) and,
2. Periodically read a memory location that can be updated by CPU to tell the kernel to exit.

This is a software watchdog.

You can use clock() or clock64() to control how often you do (1) and (2).

You can use cuda-gdb to debug your problem.

Infinite loops are not supported in the language. The compiler may be stripping code. You may want to review the PTX and SASS. If the compiler is generating bad code you can fake it out by making the compiler think there is a valid exit condition.