Deal with VkSubmitInfo sharing waitSemaphoreCount for pWaitSemaphores and pWaitDstStageMask

[voxelias]

When I construct vk::SubmitInfo and pass empty list for wait semaphores but with some wait_dst_stage_mask, the wait_semaphore_count value is being overwriten by length of the mask.

It is in vk::definitions.

    #[inline]
    pub fn wait_dst_stage_mask(mut self, wait_dst_stage_mask: &'a [PipelineStageFlags]) -> Self {
        self.wait_semaphore_count = wait_dst_stage_mask.len() as _;
        self.p_wait_dst_stage_mask = wait_dst_stage_mask.as_ptr();
        self
    }

My code:

           let mut submit_info = vk::SubmitInfo::builder()
            .wait_semaphores(&vk_wait_semaphores) // empty vector
            .wait_dst_stage_mask(&wait_dst_stage_mask)
            .command_buffers(&command_buffers)
            .signal_semaphores(&vk_signal_semaphores)
            .build();
          log::debug!(
            "buffers: {}, wait: {}, signal: {}, deps: {}",
            command_buffers.len(),
            vk_wait_semaphores.len(),
            vk_signal_semaphores.len(),
            wait_dst_stage_mask.len(),
        );

        log::debug!("Submit Info: {:?}", submit_info);

Log Output:

0.0047 ** dotrix::vulkan - buffers: 1, wait: 0, signal: 1, deps: 1
0.0047 ** dotrix::vulkan - Submit Info: SubmitInfo { s_type: SUBMIT_INFO, p_next: 0x0, wait_semaphore_count: 1, p_wait_semaphores: 0x8, p_wait_dst_stage_mask: 0x7f1726dfb96c, command_buffer_count: 1, p_command_buffers: 0x7f1710004090, signal_semaphore_count: 1, p_signal_semaphores: 0x7f1710004880 }

Workaround, otherwise it seg faults on submit:

submit_info.wait_semaphore_count = vk_wait_semaphores.len() as u32;

I would be glad to submit a PR with fix, but at the same time I have a suspicion, that p_wait_dst_stage_mask must not be an array but a pointer to a number, but I am not sure yet. Will check it tomorrow and let you know.

[MarijnS95]

If we look at the VUIDs for https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VkSubmitInfo.html:

VUID-VkSubmitInfo-pWaitSemaphores-parameter
If waitSemaphoreCount is not 0, pWaitSemaphores must be a valid pointer to an array of waitSemaphoreCount valid VkSemaphore handles

VUID-VkSubmitInfo-pWaitDstStageMask-parameter
If waitSemaphoreCount is not 0, pWaitDstStageMask must be a valid pointer to an array of waitSemaphoreCount valid combinations of VkPipelineStageFlagBits values

The list length for .wait_semaphores() and .wait_dst_stage_mask() must be equal, after all:

pWaitDstStageMask is a pointer to an array of pipeline stages at which each corresponding semaphore wait will occur.

And those semahpore waits... Come from pWaitSemaphores. It's a 1:1 mapping.

---

ash does not currently validate that they are the same, but there have been thoughts of providing a single builder function that requires all slices at once to be able to assert this: #441 (comment).

[voxelias]

I see now, so both pWaitDstStageMask and pWaitSemaphores should correlate and maintain same number of entries. Thank you!

[MarijnS95]

Yes, for each wait semaphore you can specify what stage should wait on it 👍