C Specification

To enqueue a barrier command which waits for events or commands to complete, call the function

cl_int clEnqueueBarrierWithWaitList(
    cl_command_queue command_queue,
    cl_uint num_events_in_wait_list,
    const cl_event* event_wait_list,
    cl_event* event);


  • command_queue is a valid host command-queue.

  • event_wait_list and num_events_in_wait_list specify events that need to complete before this particular command can be executed.

  • 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. The context associated with events in event_wait_list and command_queue must be the same. The memory associated with event_wait_list can be reused or freed after the function returns.

  • event returns an event object that identifies this particular command. Event objects are unique and can be used to identify this barrier command later on. 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 event_wait_list is NULL, then this particular command waits until all previous enqueued commands to command_queue have completed.

The barrier command either waits for a list of events to complete, or if the list is empty it waits for all commands previously enqueued in command_queue to complete before it completes. This command blocks command execution, that is, any following commands enqueued after it do not execute until it completes. This command returns an event which can be waited on, i.e. this event can be waited on to insure that all events either in the event_wait_list or all previously enqueued commands, queued before this command to command_queue, have completed.

clEnqueueBarrierWithWaitList returns CL_​SUCCESS if the function is successfully executed. Otherwise, it returns one of the following errors:

  • CL_​INVALID_​COMMAND_​QUEUE if command_queue is not a valid host command-queue.

  • CL_​INVALID_​CONTEXT if context associated with command_queue and events in event_wait_list are not the same.

  • 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.

See Also

Document Notes

For more information, see the OpenCL Specification

This page is extracted from the OpenCL Specification. Fixes and changes should be made to the Specification, not directly.

Copyright (c) 2014-2020 Khronos Group. This work is licensed under a Creative Commons Attribution 4.0 International License.