event
A valid event object.
command_exec_callback_type
Specifies the command execution status for which
the callback is registered. The command execution callback values for
which a callback can be registered are 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
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.
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.
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 on the queue before returning or arrange for clFlush to be called later on another thread.
Returns CL_SUCCESS if the function is executed successfully. Otherwise, it returns one of the following errors:
event
is not a valid event object.
pfn_event_notify
is NULL or if command_exec_callback_type
is not
CL_SUBMITTED
, CL_RUNNING
or
CL_COMPLETE
.