while(true)!

Accelerated Computing CUDA CUDA Programming and Performance
1

I have a question that may seem stupid to many of you, but I need it to do implement some sort of busy waiting. I have a kernel code similar to this:

global void
kernel(int *str1)
{

while(true) {
str2[0]=4;
}

}

I call this kernel from the host with grid size of 2 and block size of 6(total 12 threads). I expected this to just not do anything, basically it should hang, but surprisingly after 10 seconds the program finishes. Remember that I am actually running this on a 8400 GS card. If I run this in emulation mode, then the program never finishes, which is expected.

Can someone explain this to me please? Why does the program finish?

Thanks
Amir

2

Are you using the 8400 as a display card as well? If so, you can’t have infinite kernels because the watchdog will terminate execution.

3

Yes, I am using it as my main graphics card too. Can you explain a little more? What is watchdog?

Thanks,
Amir

4

Hi,

Watchdog is used to identify a case where the main display card is frozen - like in your case and then it suppose to

kick in and kill the offending process.

Take a look here: http://www.microsoft.com/whdc/device/displ…dm_timeout.mspx

From my experience its problematic in windows. On windows with X server it should probably work (at least long running

kernels on linux works without any problem)

If I remember correctly in a previous post, tmurray, specified that in 2.2 it should be a non issue - not sure though…

eyal

5

Uh, 2.2 has no impact on watchdog behavior. It’s still there and will always be there.