# vkCmdWaitEvents2(3) Manual Page

## Name

vkCmdWaitEvents2 - Wait for one or more events

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## C Specification

To wait for one or more events to enter the signaled state on a device, call:

    // Provided by VK_VERSION_1_3
    void vkCmdWaitEvents2(
        VkCommandBuffer                             commandBuffer,
        uint32_t                                    eventCount,
        const VkEvent*                              pEvents,
        const VkDependencyInfo*                     pDependencyInfos);

or the equivalent command

    // Provided by VK_KHR_synchronization2
    void vkCmdWaitEvents2KHR(
        VkCommandBuffer                             commandBuffer,
        uint32_t                                    eventCount,
        const VkEvent*                              pEvents,
        const VkDependencyInfo*                     pDependencyInfos);

## Parameters

- `commandBuffer` is the command buffer into which the command is recorded.

- `eventCount` is the length of the `pEvents` array.

- `pEvents` is a pointer to an array of `eventCount` events to wait on.

- `pDependencyInfos` is a pointer to an array of `eventCount` VkDependencyInfo structures, defining the second synchronization scope.

## Description

When `vkCmdWaitEvents2` is submitted to a queue, it inserts memory dependencies according to the elements of `pDependencyInfos` and each corresponding element of `pEvents`. `vkCmdWaitEvents2` must not be used to wait on event signal operations occurring on other queues, or signal operations executed by vkCmdSetEvent.

The first synchronization scope and access scope of each memory dependency defined by any element i of `pDependencyInfos` are applied to operations that occurred earlier in submission order than the last event signal operation on element i of `pEvents`.

Signal operations for an event at index i are only included if:

- The event was signaled by a vkCmdSetEvent2 command that occurred earlier in submission order with a `dependencyInfo` parameter exactly equal to the element of `pDependencyInfos` at index i ; or

- The event was created without `VK_EVENT_CREATE_DEVICE_ONLY_BIT`, and the first synchronization scope defined by the element of `pDependencyInfos` at index i only includes host operations (`VK_PIPELINE_STAGE_2_HOST_BIT`).

The second synchronization scope and access scope of each memory dependency defined by any element i of `pDependencyInfos` are applied to operations that occurred later in submission order than `vkCmdWaitEvents2`.

Note | vkCmdWaitEvents2 is used with vkCmdSetEvent2 to define a memory dependency between two sets of action commands, roughly in the same way as pipeline barriers, but split into two commands such that work between the two may execute unhindered.

Note | Applications should be careful to avoid race conditions when using events. There is no direct ordering guarantee between `vkCmdSetEvent2` and vkCmdResetEvent2, vkCmdResetEvent, or vkCmdSetEvent. Another execution dependency (e.g. a pipeline barrier or semaphore with `VK_PIPELINE_STAGE_2_ALL_COMMANDS_BIT`) is needed to prevent such a race condition.

Valid Usage

- VUID-vkCmdWaitEvents2-synchronization2-03836
  The `synchronization2` feature must be enabled

- VUID-vkCmdWaitEvents2-pEvents-03837
  Members of `pEvents` must not have been signaled by vkCmdSetEvent

- VUID-vkCmdWaitEvents2-pEvents-03838
  For any element i of `pEvents`, if that event is signaled by vkCmdSetEvent2, that command’s `dependencyInfo` parameter must be exactly equal to the ith element of `pDependencyInfos`

- VUID-vkCmdWaitEvents2-pEvents-03839
  For any element i of `pEvents`, if that event is signaled by vkSetEvent, barriers in the ith element of `pDependencyInfos` must include only host operations in their first synchronization scope

- VUID-vkCmdWaitEvents2-pEvents-03840
  For any element i of `pEvents`, if barriers in the ith element of `pDependencyInfos` include only host operations, the ith element of `pEvents` must be signaled before vkCmdWaitEvents2 is executed

- VUID-vkCmdWaitEvents2-pEvents-03841
  For any element i of `pEvents`, if barriers in the ith element of `pDependencyInfos` do not include host operations, the ith element of `pEvents` must be signaled by a corresponding vkCmdSetEvent2 that occurred earlier in submission order

- VUID-vkCmdWaitEvents2-srcStageMask-03842
  The `srcStageMask` member of any element of the `pMemoryBarriers`, `pBufferMemoryBarriers`, or `pImageMemoryBarriers` members of `pDependencyInfos` must only include pipeline stages valid for the queue family that was used to create the command pool that `commandBuffer` was allocated from

- VUID-vkCmdWaitEvents2-dstStageMask-03843
  The `dstStageMask` member of any element of the `pMemoryBarriers`, `pBufferMemoryBarriers`, or `pImageMemoryBarriers` members of `pDependencyInfos` must only include pipeline stages valid for the queue family that was used to create the command pool that `commandBuffer` was allocated from

- VUID-vkCmdWaitEvents2-dependencyFlags-03844
  If `vkCmdWaitEvents2` is being called inside a render pass instance, the `srcStageMask` member of any element of the `pMemoryBarriers`, `pBufferMemoryBarriers`, or `pImageMemoryBarriers` members of `pDependencyInfos` must not include `VK_PIPELINE_STAGE_2_HOST_BIT`

- VUID-vkCmdWaitEvents2-commandBuffer-03846
  `commandBuffer`’s current device mask must include exactly one physical device

Valid Usage (Implicit)

- VUID-vkCmdWaitEvents2-commandBuffer-parameter
  `commandBuffer` must be a valid VkCommandBuffer handle

- VUID-vkCmdWaitEvents2-pEvents-parameter
  `pEvents` must be a valid pointer to an array of `eventCount` valid VkEvent handles

- VUID-vkCmdWaitEvents2-pDependencyInfos-parameter
  `pDependencyInfos` must be a valid pointer to an array of `eventCount` valid VkDependencyInfo structures

- VUID-vkCmdWaitEvents2-commandBuffer-recording
  `commandBuffer` must be in the recording state

- VUID-vkCmdWaitEvents2-commandBuffer-cmdpool
  The `VkCommandPool` that `commandBuffer` was allocated from must support graphics, compute, decode, or encode operations

- VUID-vkCmdWaitEvents2-eventCount-arraylength
  `eventCount` must be greater than `0`

- VUID-vkCmdWaitEvents2-commonparent
  Both of `commandBuffer`, and the elements of `pEvents` must have been created, allocated, or retrieved from the same VkDevice

Host Synchronization

- Host access to `commandBuffer` must be externally synchronized

- Host access to the `VkCommandPool` that `commandBuffer` was allocated from must be externally synchronized

Command Properties

Command Buffer Levels | Render Pass Scope | Video Coding Scope | Supported Queue Types | Command Type
--- | --- | --- | --- | ---
Primary Secondary | Both | Both | Graphics Compute Decode Encode | Synchronization

## See Also

VK_KHR_synchronization2, VK_VERSION_1_3, VkCommandBuffer, VkDependencyInfo, VkEvent

## 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 2014-2024 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0