Bug report: clCreateKernelsInProgram is not thread-safe

[Bo__Yang]

When invoking clCreateKernelsInProgram to the same cl_program from many different threads. The Intel OpenCL runtime will randomly raise a CL_INVALID_VALUE error.

[Bo__Yang]

It should be thread safe according to OpenCL specification appendix A.2 ("Multiple Host Threads")

All OpenCL API calls are thread-safe except clSetKernelArg.

[Michael_C_Intel1]

Hi YangB,

Thanks for your sighting.

• Which OCL runtime are you using and for which platform? Can you identify the version and/or install package you used?
• If you're using a runtime that leverages ocl spec >= 2.0 it's slightly different, if read extremely strictly the spec's section A.2 suggests any function that modifies the state of cl_kernel objects is not thread safe.
  • Consequently, as a future proof solution I recommend staying away from unguarded clCreateKernelsInProgram calls in multiple host threads. My intent here is not to garner a discussion on how the spec should be or is, just an observation for how it can be interpreted.
  • API References:
    • ​2.0 https://www.khronos.org/registry/OpenCL/sdk/2.0/docs/man/xhtml/clCreateKernelsInProgram.html
    • 1.2 https://www.khronos.org/registry/OpenCL/sdk/1.2/docs/man/xhtml/clCreateKernelsInProgram.html
  • Spec References:
    • https://www.khronos.org/registry/OpenCL/specs/opencl-2.0.pdf​
    • https://www.khronos.org/registry/OpenCL/specs/opencl-1.2.pdf
• ​Can you give a minimal reproducer to demonstrate the issue? (While staying away from unsharable code of course?)

Thanks,

-MichaelC