Re: [PATCH v3 00/34] dmaengine: migrate channel tasklets to WQ_BH

On Mon, Aug 10, 2026 at 11:09:01AM -0700, Allen Pais wrote:
> 
> This series moves DMAengine client completion bottom halves from private
> tasklets to a common per-channel API backed by WQ_BH.
> 
> The first patch introduces the dmaengine_*_bh() API with a tasklet backend
> and converts virt-dma to it. It also updates every driver that directly
> accesses the removed virt_dma_chan tasklet, keeping the patch buildable on
> its own. This separates the driver-facing API from its implementation
> without changing callback context.
> 
> The second patch switches that backend to a dedicated WQ_BH | WQ_PERCPU
> workqueue. WQ_BH keeps callbacks in softirq context, while the common API
> centralizes initialization, scheduling, and synchronization. The
> workqueue helpers remain internal to DMAengine, and dmaengine_kill_bh()
> drains scheduled callbacks to preserve tasklet_kill() semantics.
> 
> The remaining patches convert driver-owned channel completion tasklets.
> Tasklets used for controller-level processing, recovery, or other
> non-client-callback work are deliberately left alone because the
> appropriate replacement may differ by driver.

Right, I would actually expect that virt-dma (and others will follow the
example) will switch to threaded IRQ instead of tasklets.

> As agreed in the RFC discussion, selecting hardirq callback delivery is a
> separate API change and is not part of this series.

-- 
With Best Regards,
Andy Shevchenko