cl_int clSetEventCallback(cl_event event, cl_int command_exec_callback_type, void (CL_CALLBACK *pfn_event_notify) (cl_event event, cl_int event_command_exec_status, void *user_data), void *user_data);

PARAMETERS

event

A valid event object.

command_exec_callback_type

The command execution status for which the callback is registered. The command execution callback value for which a callback can be registered is CL_SUBMITTED, CL_RUNNING, or CL_COMPLETE. There is no guarantee that the callback functions registered for various execution status values for an event will be called in the exact order that the execution status of a command changes. Furthermore, it should be noted that receiving a call back for an event with a status other than CL_COMPLETE, in no way implies that the memory model or execution model as defined by the OpenCL specification has changed. For example, it is not valid to assume that a corresponding memory transfer has completed unless the event is in a state CL_COMPLETE.

The callback function registered for a command_exec_callback_type value of CL_COMPLETE will be called when the command has completed successfully or is abnormally terminated.

pfn_event_notify

The event 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:

• event is the event object for which the callback function is invoked.

• event_command_exec_status represents the execution status of command for which this callback function is invoked. See the table of values for param_value for clGetEventInfo(3clc) for the command execution status values. If the callback is called as the result of the command associated with event being abnormally terminated, an appropriate error code for the error that caused the termination will be passed to event_command_exec_status instead.

• user_data is a pointer to user supplied data.

user_data

Will be passed as the user_data argument when pfn_notify is called. user_data can be NULL.

NOTES

The registered callback function will be called when the execution status of command associated with event changes to an execution status equal to or past the status specified by command_exec_status.

Each call to clSetEventCallback registers the specified user callback function on a callback stack associated with event. The order in which the registered user callback functions are called is undefined.

All callbacks registered for an event object must be called. All enqueued callbacks shall be called before the event object is destroyed. Callbacks must return promptly. 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), and 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).

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.

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 183, section 5.9 - Event Objects