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Cannot Access OpenCL FAQ Online Documentation

Shang Li
Intellectual 400 points


Hi,

I'm running an OpenCL program and got the error print outs like: Waiting on lock /var/lock/opencl... and then the program stuck there.

I googled and it turns out there is a FAQ page on your OpenCL online documentation that says about it. But I couldn't open it,

Every time I tried to open it it gave me a 403 error and says:

Forbidden

You don't have permission to access /mctools/docs/opencl/faq/index.html on this server.

Can anybody help me with that?

Thanks,

Shang

  • 0
    TI__Expert 3350 points
    Shang,

    Thank you for making us aware of the permission issue, it's been fixed. However, there is a delay before the update is externally visible. I'll let you know when that happens (in the next hour or two).

    In the meantime, here is the answer to your question.

    Why do I get messages about /var/lock/opencl when running OpenCL applications?

    The TI OpenCL implementation currently allows only 1 OpenCL enabled process to execute at any given time. To enforce this, The OpenCL implementation locks the file /var/local/opencl when an OpenCL application begins and frees it when it completes. If two OpenCL processes attempt to run concurrently, then one will block waiting for the file lock to be released. It is possible for an OpenCL application to terminate abnormally and leave the locked file in place. If you determine that no other OpenCL process is running and your OpenCL application still recevies the waiting on /var/lock/opencl message, then the /var/lock/opencl file can be safely removed to allow your process to continue.

    Ajay
  • 0 in reply to Ajay Jayaraj
    Intellectual 400 points

    Hi Ajay,

    Thanks for your prompt reply and actions!

    Then I guess a further question would be, I'm running an application that uses both OpenMPI and OpenCL, and it's running on a shared NFS through multiple k2h nodes, then when each node/process would try to call an OpenCL-built library, would that always lead to this situation?

    Thanks,

    Shang

  • 0 in reply to Shang Li
    TI__Expert 3350 points

    Shang,

    The fix to the website is now visible externally.

    The /var/lock folder is located on the tmpfs file system and each node has it's own copy, typically in ram or swap. So, there should be no conflict on /var/lock due to shared NFS.

    Ajay

  • 0 in reply to Ajay Jayaraj
    TI__Intellectual 1400 points

    Shang,

    If you run multiple MPI ranks on a single K2H node, you will see this error.   To concurrently use OpenCL and OpenMPI, you must limit ranks to one per K2H device. 

    Alan