clEnqueueAcquireGLObjects(3clc)
NAME
clEnqueueAcquireGLObjects - Acquire OpenCL memory objects that have
been created from OpenGL objects.
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.
ERRORS
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), clEnqueueReleaseGLObjects(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 56, section 9.7.6 - Sharing memory objects that map to GL
objects...
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