cl_int clEnqueueAcquireGLObjects(cl_command_queue command_queue, cl_uint num_objects, const cl_mem *mem_objects, cl_uint num_events_in_wait_list, const cl_event *event_wait_list, cl_event *event);

PARAMETERS

command_queue

A valid command-queue. All devices used to create the OpenCL context associated with command_queue must support acquiring shared CL/GL objects. This constraint is enforced at context creation time.

num_objects

The number of memory objects to be acquired in mem_objects.

mem_objects

A pointer to a list of CL memory objects that correspond to GL objects.

event_wait_list , num_events_in_wait_list

and Specify events that need to complete before this particular command can be executed. If event_wait_list is NULL, then this particular command does not wait on any event to complete. If event_wait_list is NULL, num_events_in_wait_list must be 0. If event_wait_list is not NULL, the list of events pointed to by event_wait_list must be valid and num_events_in_wait_list must be greater than 0. The events specified in event_wait_list act as synchronization points.

event

Returns an event object that identifies this command and can be used to query or queue a wait for the command to complete. event can be NULL in which case it will not be possible for the application to query the status of this command or queue a wait for this command to complete. If the event_wait_list and the event arguments are not NULL, the event argument should not refer to an element of the event_wait_list array

If the cl_khr_gl_sharing(3clc) extension is supported, if an OpenGL context is bound to the current thread, then any OpenGL commands which

•

affect or access the contents of a memory object listed in the mem_objects list, and

•

were issued on that OpenGL context prior to the call to clEnqueueAcquireGLObjects.RE

will complete before execution of any OpenCL commands following the clEnqueueAcquireGLObjects which affect or access any of those memory objects. If a non-NULL event object is returned, it will report completion only after completion of such OpenGL commands.

DESCRIPTION

These objects need to be acquired before they can be used by any OpenCL commands queued to a command-queue. The OpenGL objects are acquired by the OpenCL context associated with command_queue and can therefore be used by all command-queues associated with the OpenCL context.

NOTES

In order to ensure data integrity, the application is responsible for synchronizing access to shared CL/GL objects by their respective APIs. Failure to provide such synchronization may result in race conditions and other undefined behavior including non-portability between implementations.

Prior to calling clEnqueueAcquireGLObjects, the application must ensure that any pending GL operations which access the objects specified in mem_objects have completed. This may be accomplished portably by issuing and waiting for completion of a glFinish command on all GL contexts with pending references to these objects. Implementations may offer more efficient synchronization methods; for example on some platforms calling glFlush may be sufficient, or synchronization may be implicit within a thread, or there may be vendor-specific extensions that enable placing a fence in the GL command stream and waiting for completion of that fence in the CL command queue. Note that no synchronization methods other than glFinish are portable between OpenGL implementations at this time.

Similarly, after calling clEnqueueReleaseGLObjects, the application is responsible for ensuring that any pending OpenCL operations which access the objects specified in mem_objects have completed prior to executing subsequent GL commands which reference these objects. This may be accomplished portably by calling clWaitForEvents(3clc) with the event object returned by clEnqueueReleaseGLObjects, or by calling clFinish(3clc). As above, some implementations may offer more efficient methods.

The application is responsible for maintaining the proper order of operations if the CL and GL contexts are in separate threads.

If a GL context is bound to a thread other than the one in which clEnqueueReleaseGLObjects is called, changes to any of the objects in mem_objects may not be visible to that context without additional steps being taken by the application. For an OpenGL 3.1 (or later) context, the requirements are described in Appendix D ("Shared Objects and Multiple Contexts") of the OpenGL 3.1 Specification. For prior versions of OpenGL, the requirements are implementation-dependent.

Attempting to access the data store of an OpenGL object after it has been acquired by OpenCL and before it has been released will result in undefined behavior. Similarly, attempting to access a shared CL/GL object from OpenCL before it has been acquired by the OpenCL command queue, or after it has been released, will result in undefined behavior.

If the cl_khr_gl_event(3clc) extension is supported, then the OpenCL implementation will ensure that any such pending OpenGL operations are complete for an OpenGL context bound to the same thread as the OpenCL context. This is referred to as implicit synchronization.

SPECIFICATION

m[blue]OpenCL Specificationm[][1]

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 56, section 9.7.6 - Sharing memory objects that map to GL objects...