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Thread: safe deleting cpu data

  1. #1
    Junior Member
    Join Date
    May 2012
    Posts
    1

    safe deleting cpu data

    I have some code like this:

    Code :
    buffer = clCreateBuffer( ... );
    ...
    float* temp = new float[ size ];
    ...
    clEnqueueWriteBuffer( ..., temp, ... );
     
    clEnqueueBarrier( cq );
     
    kernel = clCreateKernel( prog, "mykernel", ... );
    clSetKernelArg( kernel, ..., &buffer );
    clEnqueueNDRangeKernel( kernel, .... );
     
    delete[] temp;  <--------- safe?

    My question is: Without using events and clWaitForEvents(), where can I do delete my cpu buffer being sure that the cpu->gpu copy (clEnqueuWriteBuffer) has finished?

    In my code I delete the cpu buffer after the execution of a kernel that must wait for the previous enqueued command (that copies "buffer" from cpu to gpu). Both clEnqueueWriteBuffer and clEnqueueNDRangeKernel are asynchronous, so my doubt is ┐does clEnqueueNDRangeKernel stall until clEnqueueWriteBuffer has finished?

  2. #2
    Senior Member
    Join Date
    Aug 2011
    Posts
    271

    Re: safe deleting cpu data

    You have to use events, or some other mechanism which synchronises the calls (e.g. job completion).

    All the 'enqueue' commands - not surprisingly - only enqueue requests, they do not wait for anything. The only guarantee is that the copy will be finished before the kernel is executed: but neither has any synchronisation relation to the host code (enqueue calls).

    I tend to allocate all buffers necessary for a task and keep them around until i'm well and truly done. Or use events to arbitrate.

    You could use event callbacks or a cleanup thread (which synchronisly waits on the events) if you want explicit control.

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