C Specification

To enqueue a command to indicate that the host has completed updating the region given by svm_ptr and which was specified in a previous call to clEnqueueSVMMap, call the function

// Provided by CL_VERSION_2_0
cl_int clEnqueueSVMUnmap(
    cl_command_queue command_queue,
    void* svm_ptr,
    cl_uint num_events_in_wait_list,
    const cl_event* event_wait_list,
    cl_event* event);
clEnqueueSVMUnmap is missing before version 2.0.

Parameters

  • command_queue must be a valid host command-queue.

  • svm_ptr is a pointer that was specified in a previous call to clEnqueueSVMMap. If svm_ptr is allocated using clSVMAlloc then it must be allocated from the same context from which command_queue was created. Otherwise the behavior is undefined.

  • event_wait_list and num_events_in_wait_list specify events that need to complete before clEnqueueSVMUnmap can be executed. If event_wait_list is NULL, then clEnqueueSVMUnmap 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. 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 command and can be used to query or queue a wait for this command to complete. If event is NULL or the enqueue is unsuccessful, no event will be created and therefore it will not be possible to query the status of this command or to wait for this command to complete. If event_wait_list and event are not NULL, event must not refer to an element of the event_wait_list array.

Description

clEnqueueSVMMap and clEnqueueSVMUnmap act as synchronization points for the region of the SVM buffer specified in these calls.

clEnqueueSVMUnmap returns CL_SUCCESS if the function is executed successfully. Otherwise, it returns one of the following errors:

  • CL_INVALID_COMMAND_QUEUE if command_queue is not a valid host command-queue.

  • CL_INVALID_OPERATION if the device associated with command_queue does not support SVM.

  • CL_INVALID_CONTEXT if context associated with command_queue and events in event_wait_list are not the same.

  • CL_INVALID_VALUE if svm_ptr is NULL.

  • CL_INVALID_EVENT_WAIT_LIST if event_wait_list is NULL and num_events_in_wait_list > 0, or if 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.

If a coarse-grained SVM buffer is currently mapped for writing, the application must ensure that the SVM buffer is unmapped before any enqueued kernels or commands that read from or write to this SVM buffer or any of its associated cl_mem buffer objects begin execution; otherwise the behavior is undefined.

If a coarse-grained SVM buffer is currently mapped for reading, the application must ensure that the SVM buffer is unmapped before any enqueued kernels or commands that write to this memory object or any of its associated cl_mem buffer objects begin execution; otherwise the behavior is undefined.

A SVM buffer is considered as mapped if there are one or more active mappings for the SVM buffer irrespective of whether the mapped regions span the entire SVM buffer.

The above note does not apply to fine-grained SVM buffers (fine-grained buffers allocated using clSVMAlloc or fine-grained system allocations).

See Also

CL_VERSION_2_0, cl_command_queue, cl_event, cl_uint

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

Copyright 2014-2025 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0