NAME

       clSetMemObjectDestructorCallback - Registers a user callback function with a memory
       object.

       cl_int clSetMemObjectDestructorCallback(cl_mem memobj,
                                               void (CL_CALLBACK *pfn_notify) (cl_mem memobj,
                                               void *user_data), void *user_data);

PARAMETERS

       memobj
           A valid memory object.

       pfn_notify
           The callback function that can be registered by the application. This callback
           function may be called asynchronously by the OpenCL implementation. It is the
           application's responsibility to ensure that the callback function is thread-safe. The
           parameters to this callback function are:

           •   memobj: the memory object being deleted.  When the user callback is called by the
               implementation, this memory object is no longer valid.  memobj is only provided
               for reference purposes.

           •   user_data: a pointer to user supplied data.

       user_data
           Data which will be passed as the user_data argument when pfn_notify is called.
           user_data can be NULL.

NOTES

       Each call to clSetMemObjectDestructorCallback registers the specified user callback
       function on a callback stack associated with memobj. The registered user callback
       functions are called in the reverse order in which they were registered. The user callback
       functions are called and then the memory object's resources are freed and the memory
       object is deleted. This provides a mechanism for the application (and libraries) using
       memobj to be notified when the memory referenced by host_ptr, specified when the memory
       object is created and used as the storage bits for the memory object, can be reused or
       freed.

       When the user callback function is called by the implementation, the contents of the
       memory region pointed to by host_ptr (if the memory object is created with
       CL_MEM_USE_HOST_PTR) are undefined. The callback function is typically used by the
       application to either free or reuse the memory region pointed to by host_ptr.

       The behavior of calling expensive system routines, OpenCL API calls to create contexts or
       command-queues, or blocking OpenCL operations from the following list below, in a callback
       is undefined.

       •   clFinish(3clc).RE

           •   clWaitForEvents(3clc).RE

               •    blocking calls to clEnqueueReadBuffer(3clc), clEnqueueReadBufferRect(3clc),
                   clEnqueueWriteBuffer(3clc), clEnqueueWriteBufferRect(3clc).RE

                   •    blocking calls to clEnqueueReadImage(3clc) and
                       clEnqueueWriteImage(3clc).RE

                       •    blocking calls to clEnqueueMapBuffer(3clc) and
                           clEnqueueMapImage(3clc).RE

                           •    blocking calls to clBuildProgram(3clc), clCompileProgram(3clc),
                               or clLinkProgram(3clc).RE

                               If an application needs to wait for completion of a routine from
                               the above list in a callback, please use the non-blocking form of
                               the function, and assign a completion callback to it to do the
                               remainder of your work. Note that when a callback (or other code)
                               enqueues commands to a command-queue, the commands are not
                               required to begin execution until the queue is flushed. In
                               standard usage, blocking enqueue calls serve this role by
                               implicitly flushing the queue. Since blocking calls are not
                               permitted in callbacks, those callbacks that enqueue commands on a
                               command queue should either call clFlush(3clc) on the queue before
                               returning or arrange for clFlush(3clc) to be called later on
                               another thread.

                               The user callback function may not call OpenCL APIs with the
                               memory object for which the callback function is invoked and for
                               such cases the behavior of OpenCL APIs is considered to be
                               undefined.

ERRORS

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

       •   CL_INVALID_MEM_OBJECT if memobj is not a valid memory object.

       •   CL_INVALID_VALUE if pfn_notify is NULL.

       •   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[1]

SEE ALSO

       clCreateCommandQueue(3clc), clGetCommandQueueInfo(3clc), clReleaseCommandQueue(3clc),
       clRetainCommandQueue(3clc)

AUTHORS

       The Khronos Group

COPYRIGHT

       Copyright © 2007-2011 The Khronos Group Inc.
       Permission is hereby granted, free of charge, to any person obtaining a copy of this
       software and/or associated documentation files (the "Materials"), to deal in the Materials
       without restriction, including without limitation the rights to use, copy, modify, merge,
       publish, distribute, sublicense, and/or sell copies of the Materials, and to permit
       persons to whom the Materials are furnished to do so, subject to the condition that this
       copyright notice and permission notice shall be included in all copies or substantial
       portions of the Materials.

NOTES

        1. OpenCL Specification
           page 119, section 5.4.1 - Retaining and Releasing Memory Objects