# vkDeferredOperationJoinKHR(3) Manual Page

## Name

vkDeferredOperationJoinKHR - Assign a thread to a deferred operation

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## C Specification

To assign a thread to a deferred operation, call:

    // Provided by VK_KHR_deferred_host_operations
    VkResult vkDeferredOperationJoinKHR(
        VkDevice                                    device,
        VkDeferredOperationKHR                      operation);

## Parameters

- `device` is the device which owns `operation`.

- `operation` is the deferred operation that the calling thread should work on.

## Description

The `vkDeferredOperationJoinKHR` command will execute a portion of the deferred operation on the calling thread.

The return value will be one of the following:

- A return value of `VK_SUCCESS` indicates that `operation` is complete. The application should use vkGetDeferredOperationResultKHR to retrieve the result of `operation`.

- A return value of `VK_THREAD_DONE_KHR` indicates that the deferred operation is not complete, but there is no work remaining to assign to threads. Future calls to vkDeferredOperationJoinKHR are not necessary and will simply harm performance. This situation may occur when other threads executing vkDeferredOperationJoinKHR are about to complete `operation`, and the implementation is unable to partition the workload any further.

- A return value of `VK_THREAD_IDLE_KHR` indicates that the deferred operation is not complete, and there is no work for the thread to do at the time of the call. This situation may occur if the operation encounters a temporary reduction in parallelism. By returning `VK_THREAD_IDLE_KHR`, the implementation is signaling that it expects that more opportunities for parallelism will emerge as execution progresses, and that future calls to vkDeferredOperationJoinKHR can be beneficial. In the meantime, the application can perform other work on the calling thread.

Implementations must guarantee forward progress by enforcing the following invariants:

1. If only one thread has invoked vkDeferredOperationJoinKHR on a given operation, that thread must execute the operation to completion and return `VK_SUCCESS`.

2. If multiple threads have concurrently invoked vkDeferredOperationJoinKHR on the same operation, then at least one of them must complete the operation and return `VK_SUCCESS`.

Valid Usage (Implicit)

- VUID-vkDeferredOperationJoinKHR-device-parameter
  `device` must be a valid VkDevice handle

- VUID-vkDeferredOperationJoinKHR-operation-parameter
  `operation` must be a valid VkDeferredOperationKHR handle

- VUID-vkDeferredOperationJoinKHR-operation-parent
  `operation` must have been created, allocated, or retrieved from `device`

Return Codes

On success, this command returns

  - `VK_SUCCESS`

  - `VK_THREAD_DONE_KHR`

  - `VK_THREAD_IDLE_KHR`

On failure, this command returns

  - `VK_ERROR_OUT_OF_HOST_MEMORY`

  - `VK_ERROR_OUT_OF_DEVICE_MEMORY`

## See Also

VK_KHR_deferred_host_operations, VkDeferredOperationKHR, VkDevice

## Document Notes

For more information, see the Vulkan Specification

This page is extracted from the Vulkan 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