clSetKernelArgSVMPointer

Used to set a SVM pointer as the argument value for a specific argument of a kernel.

cl_int clSetKernelArgSVMPointer ( cl_kernel kernel,
  cl_uint arg_index,
  const void *arg_value)

Parameters

kernel

A valid kernel object.

arg_index

The argument index. Arguments to the kernel are referred by indices that go from 0 for the leftmost argument to n - 1, where n is the total number of arguments declared by a kernel.

arg_value

The SVM pointer that should be used as the argument value for argument specified by arg_index. The SVM pointer specified is the value used by all API calls that enqueue kernel (clEnqueueNDRangeKernel) until the argument value is changed by a call to clSetKernelArgSVMPointer for kernel. The SVM pointer can only be used for arguments that are declared to be a pointer to global or constant memory. The SVM pointer value must be aligned according to the argument type. For example, if the argument is declared to be global float4 *p, the SVM pointer value passed for p must be at a minimum aligned to a float4. The SVM pointer value specified as the argument value can be the pointer returned by clSVMAlloc or can be a pointer + offset into the SVM region.

Notes

All OpenCL API calls are thread-safe except clSetKernelArg and clSetKernelArgSVMPointer. clSetKernelArg and clSetKernelArgSVMPointer are safe to call from any host thread, and safe to call re-entrantly so long as concurrent calls operate on different cl_kernel objects. However, the behavior of the cl_kernel object is undefined if clSetKernelArg or clSetKernelArgSVMPointer are called from multiple host threads on the same cl_kernel object at the same time. Please note that there are additional limitations as to which OpenCL APIs may be called from OpenCL callback functions -- please see section 5.11. (Please refer to the OpenCL glossary for the OpenCL definition of thread-safe. This definition may be different from usage of the term in other contexts.)

There is an inherent race condition in the design of OpenCL that occurs between setting a kernel argument and using the kernel with clEnqueueNDRangeKernel. Another host thread might change the kernel arguments between when a host thread sets the kernel arguments and then enqueues the kernel, causing the wrong kernel arguments to be enqueued. Rather than attempt to share cl_kernel objects among multiple host threads, applications are strongly encouraged to make additional cl_kernel objects for kernel functions for each host thread.

Errors

clSetKernelArgSVMPointer returns CL_SUCCESS if the function is executed successfully. Otherwise, it returns one of the following errors:

  • CL_INVALID_KERNEL if kernel is not a valid kernel object.
  • CL_INVALID_ARG_INDEX if arg_index is not a valid argument index.
  • CL_INVALID_ARG_VALUE if arg_value specified is not a valid value.
  • CL_OUT_OF_RESOURCES if there is a failure to allocate resources required by the OpenCL implementation on the device.
  • CL_OUT_OF_HOST_MEMORY if there is a failure to allocate resources required by the OpenCL implementation on the host.

Specification

OpenCL Specification

Also see

clSetKernelArg, clCreateKernel, clCreateKernelsInProgram, clReleaseKernel, clRetainKernel, clGetKernelInfo, clGetKernelWorkGroupInfo

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