need help with gpu code

Im trying to use mutex in my code with no luck. Matlab says that kernel reaches timeout.

kernel:

__global__ void getGrid(    int*   mask,
                int*  mutex  )  {

      unsigned int idx = blockIdx.x * blockDim.x + threadIdx.x;

      while( idx < 100 ){

        while( atomicCAS( mutex, 0, 1 ) != 0 );
          mask[ idx ] = idx;

        atomicExch( mutex, 0 );
        //*mutex = 0;
        //while( atomicCAS( mutex, idx, idx + 1 ) != idx );

        idx += blockDim.x * gridDim.x;

        }

      }

script:

mutex       = parallel.gpu.GPUArray.zeros('int32');
kern0 = parallel.gpu.CUDAKernel('testkern.ptx', 'testkern.cu');
kern0.ThreadBlockSize = [256 1 1];
kern0.GridSize = [7*20 1];
mask = parallel.gpu.GPUArray.zeros(int32(256*7*20),int32(1),'int32');
tic
[mask mutex] = feval(kern0, mask, mutex);
toc

Commented atomicCAS works properly, but first one don't. Any mistakes or.. ?

[Walter Roberson]

Are you running the card in "service mode", or is it shared for graphics? Service mode is available on Telsa, but not GT / GTX (I do not know about Quadro.)

[m4 Chrennikov]

It is shared for graphics but this is not the cause.

[Konrad Malkowski]

Does this work outside of MATLAB?