oracular (3) clEnqueueReleaseGLObjects.3clc.gz
NAME
clEnqueueReleaseGLObjects - Release OpenCL memory objects that have been created from OpenGL objects.
cl_int clEnqueueReleaseGLObjects(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.
num_objects
The number of memory objects to be released 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
These parameters specify events that need to complete before this 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 particular read/write 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 cl_khr_gl_sharing(3clc) extension is supported and if an OpenGL context is bound to the
current thread, then any OpenGL commands which does:
• affect or access the contents of a memory object listed in the mem_objects list, and
• are issued on that context after the call to clEnqueueReleaseGLObjects.RE
will not execute until after execution of any OpenCL commands preceding the
clEnqueueReleaseGLObjects which affect or access any of those memory objects. If a non-NULL event
object is returned, it will report completion before execution of such OpenGL commands.
DESCRIPTION
Release OpenCL memory objects that have been created from OpenGL objects. These objects need to be
released before they can be used by OpenGL. The OpenGL objects are released by the OpenCL context
associated with command_queue.
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.
ERRORS
clEnqueueReleaseGLObjects returns CL_SUCCESS if the function is executed successfully. If num_objects is
0 and mem_objects is NULL the function does nothing and returns CL_SUCCESS. Otherwise, it returns one of
the following errors:
• CL_INVALID_VALUE if num_objects is zero and mem_objects is not a NULL value or if num_objects > 0 and
mem_objects is NULL.
• CL_INVALID_MEM_OBJECT if memory objects in mem_objects are not valid OpenCL memory objects.
• CL_INVALID_COMMAND_QUEUE if command_queue is not a valid command-queue.
• CL_INVALID_CONTEXT if context associated with command_queue was not created from an OpenGL context.
• CL_INVALID_GL_OBJECT if memory objects in mem_objects have not been created from a GL object(s).
• CL_INVALID_EVENT_WAIT_LIST if event_wait_list is NULL and num_events_in_wait_list > 0, or
event_wait_list is not NULL and num_events_in_wait_list is 0, or if event objects in event_wait_list
are not valid events.
• 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
cl_khr_gl_sharing(3clc), clEnqueueAcquireGLObjects(3clc), cl_khr_gl_event(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 58, section 9.7.6 - Sharing memory objects that map to GL objects...