# vkCmdWaitEvents(3) Manual Page

## Name

vkCmdWaitEvents - Wait for one or more events and insert a set of memory

## C Specification

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

    void vkCmdWaitEvents(
        VkCommandBuffer                             commandBuffer,
        uint32_t                                    eventCount,
        const VkEvent*                              pEvents,
        VkPipelineStageFlags                        srcStageMask,
        VkPipelineStageFlags                        dstStageMask,
        uint32_t                                    memoryBarrierCount,
        const VkMemoryBarrier*                      pMemoryBarriers,
        uint32_t                                    bufferMemoryBarrierCount,
        const VkBufferMemoryBarrier*                pBufferMemoryBarriers,
        uint32_t                                    imageMemoryBarrierCount,
        const VkImageMemoryBarrier*                 pImageMemoryBarriers);

## 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 event object handles to wait on.

- `srcStageMask` is a bitmask of VkPipelineStageFlagBits specifying the source stage mask.

- `dstStageMask` is a bitmask of VkPipelineStageFlagBits specifying the destination stage mask.

- `memoryBarrierCount` is the length of the `pMemoryBarriers` array.

- `pMemoryBarriers` is a pointer to an array of VkMemoryBarrier structures.

- `bufferMemoryBarrierCount` is the length of the `pBufferMemoryBarriers` array.

- `pBufferMemoryBarriers` is a pointer to an array of VkBufferMemoryBarrier structures.

- `imageMemoryBarrierCount` is the length of the `pImageMemoryBarriers` array.

- `pImageMemoryBarriers` is a pointer to an array of VkImageMemoryBarrier structures.

## Description

When `vkCmdWaitEvents` is submitted to a queue, it defines a memory dependency between prior event signal operations on the same queue or the host, and subsequent commands. `vkCmdWaitEvents` must not be used to wait on event signal operations occurring on other queues.

The first synchronization scope only includes event signal operations that operate on members of `pEvents`, and the operations that happened-before the event signal operations. Event signal operations performed by vkCmdSetEvent that occur earlier in submission order are included in the first synchronization scope, if the logically latest pipeline stage in their `stageMask` parameter is logically earlier than or equal to the logically latest pipeline stage in `srcStageMask`. Event signal operations performed by vkSetEvent are only included in the first synchronization scope if `VK_PIPELINE_STAGE_HOST_BIT` is included in `srcStageMask`.

The second synchronization scope includes all commands that occur later in submission order. The second synchronization scope is limited to operations on the pipeline stages determined by the destination stage mask specified by `dstStageMask`.

The first access scope is limited to access in the pipeline stages determined by the source stage mask specified by `srcStageMask`. Within that, the first access scope only includes the first access scopes defined by elements of the `pMemoryBarriers`, `pBufferMemoryBarriers` and `pImageMemoryBarriers` arrays, which each define a set of memory barriers. If no memory barriers are specified, then the first access scope includes no accesses.

The second access scope is limited to access in the pipeline stages determined by the destination stage mask specified by `dstStageMask`. Within that, the second access scope only includes the second access scopes defined by elements of the `pMemoryBarriers`, `pBufferMemoryBarriers` and `pImageMemoryBarriers` arrays, which each define a set of memory barriers. If no memory barriers are specified, then the second access scope includes no accesses.

| Note vkCmdWaitEvents is used with vkCmdSetEvent 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. Unlike vkCmdPipelineBarrier, a queue family ownership transfer cannot be performed using vkCmdWaitEvents.

| Note Applications should be careful to avoid race conditions when using events. There is no direct ordering guarantee between a vkCmdResetEvent command and a vkCmdWaitEvents command submitted after it, so some other execution dependency must be included between these commands (e.g. a semaphore).

Valid Usage

- `srcStageMask` must be the bitwise OR of the `stageMask` parameter used in previous calls to `vkCmdSetEvent` with any of the members of `pEvents` and `VK_PIPELINE_STAGE_HOST_BIT` if any of the members of `pEvents` was set using `vkSetEvent`

- If the geometry shaders feature is not enabled, `srcStageMask` must not contain `VK_PIPELINE_STAGE_GEOMETRY_SHADER_BIT`

- If the geometry shaders feature is not enabled, `dstStageMask` must not contain `VK_PIPELINE_STAGE_GEOMETRY_SHADER_BIT`

- If the tessellation shaders feature is not enabled, `srcStageMask` must not contain `VK_PIPELINE_STAGE_TESSELLATION_CONTROL_SHADER_BIT` or `VK_PIPELINE_STAGE_TESSELLATION_EVALUATION_SHADER_BIT`

- If the tessellation shaders feature is not enabled, `dstStageMask` must not contain `VK_PIPELINE_STAGE_TESSELLATION_CONTROL_SHADER_BIT` or `VK_PIPELINE_STAGE_TESSELLATION_EVALUATION_SHADER_BIT`

- If `pEvents` includes one or more events that will be signaled by `vkSetEvent` after `commandBuffer` has been submitted to a queue, then `vkCmdWaitEvents` must not be called inside a render pass instance

- Any pipeline stage included in `srcStageMask` or `dstStageMask` must be supported by the capabilities of the queue family specified by the `queueFamilyIndex` member of the VkCommandPoolCreateInfo structure that was used to create the `VkCommandPool` that `commandBuffer` was allocated from, as specified in the table of supported pipeline stages.

- Each element of `pMemoryBarriers`, `pBufferMemoryBarriers` or `pImageMemoryBarriers` must not have any access flag included in its `srcAccessMask` member if that bit is not supported by any of the pipeline stages in `srcStageMask`, as specified in the table of supported access types.

- Each element of `pMemoryBarriers`, `pBufferMemoryBarriers` or `pImageMemoryBarriers` must not have any access flag included in its `dstAccessMask` member if that bit is not supported by any of the pipeline stages in `dstStageMask`, as specified in the table of supported access types.

- The `srcQueueFamilyIndex` and `dstQueueFamilyIndex` members of any element of `pBufferMemoryBarriers` or `pImageMemoryBarriers` must be equal.

- `commandBuffer`’s current device mask must include exactly one physical device.

- If the mesh shaders feature is not enabled, `srcStageMask` must not contain `VK_PIPELINE_STAGE_MESH_SHADER_BIT_NV`

- If the task shaders feature is not enabled, `srcStageMask` must not contain `VK_PIPELINE_STAGE_TASK_SHADER_BIT_NV`

- If the mesh shaders feature is not enabled, `dstStageMask` must not contain `VK_PIPELINE_STAGE_MESH_SHADER_BIT_NV`

- If the task shaders feature is not enabled, `dstStageMask` must not contain `VK_PIPELINE_STAGE_TASK_SHADER_BIT_NV`

- The `srcAccessMask` member of each element of `pMemoryBarriers` must only include access flags that are supported by one or more of the pipeline stages in `srcStageMask`, as specified in the table of supported access types

- The `dstAccessMask` member of each element of `pMemoryBarriers` must only include access flags that are supported by one or more of the pipeline stages in `dstStageMask`, as specified in the table of supported access types

- The `srcAccessMask` member of each element of `pBufferMemoryBarriers` must only include access flags that are supported by one or more of the pipeline stages in `srcStageMask`, as specified in the table of supported access types

- The `dstAccessMask` member of each element of `pBufferMemoryBarriers` must only include access flags that are supported by one or more of the pipeline stages in `dstStageMask`, as specified in the table of supported access types

- The `srcAccessMask` member of each element of `pImageMemoryBarriers` must only include access flags that are supported by one or more of the pipeline stages in `srcStageMask`, as specified in the table of supported access types

- The `dstAccessMask` member of any element of `pImageMemoryBarriers` must only include access flags that are supported by one or more of the pipeline stages in `dstStageMask`, as specified in the table of supported access types

Valid Usage (Implicit)

- `commandBuffer` must be a valid VkCommandBuffer handle

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

- `srcStageMask` must be a valid combination of VkPipelineStageFlagBits values

- `srcStageMask` must not be `0`

- `dstStageMask` must be a valid combination of VkPipelineStageFlagBits values

- `dstStageMask` must not be `0`

- If `memoryBarrierCount` is not `0`, `pMemoryBarriers` must be a valid pointer to an array of `memoryBarrierCount` valid VkMemoryBarrier structures

- If `bufferMemoryBarrierCount` is not `0`, `pBufferMemoryBarriers` must be a valid pointer to an array of `bufferMemoryBarrierCount` valid VkBufferMemoryBarrier structures

- If `imageMemoryBarrierCount` is not `0`, `pImageMemoryBarriers` must be a valid pointer to an array of `imageMemoryBarrierCount` valid VkImageMemoryBarrier structures

- `commandBuffer` must be in the recording state

- The `VkCommandPool` that `commandBuffer` was allocated from must support graphics, or compute operations

- `eventCount` must be greater than `0`

- 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 | Supported Queue Types | Pipeline Type
--- | --- | --- | ---
Primary Secondary | Both | Graphics Compute |

## See Also

VkBufferMemoryBarrier, VkCommandBuffer, VkEvent, VkImageMemoryBarrier, VkMemoryBarrier, VkPipelineStageFlags

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