Bug report: clCreateKernelsInProgram is not thread-safe

Bo__Yang — Mon, 26 Mar 2018 03:53:58 GMT

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

It should be thread safe

Bo__Yang — Mon, 26 Mar 2018 03:59:43 GMT

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

All OpenCL API calls are thread-safe except clSetKernelArg.

Hi YangB,

Michael_C_Intel1 — Tue, 27 Mar 2018 21:47:36 GMT

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

topic Bug report: clCreateKernelsInProgram is not thread-safe in OpenCL* for CPU

Bug report: clCreateKernelsInProgram is not thread-safe

It should be thread safe

Hi YangB,