Re: [PATCH v2 01/10] workqueue: devres: Add device-managed allocate workqueue

[Tejun Heo <tj@kernel.org>]

On Thu, Mar 05, 2026 at 10:45:40PM +0100, Krzysztof Kozlowski wrote:
> Add a Resource-managed version of alloc_workqueue() to fix common
> problem of drivers mixing devm() calls with destroy_workqueue.  Such
> naive and discouraged driver approach leads to difficult to debug bugs
> when the driver:
> 
> 1. Allocates workqueue in standard way and destroys it in driver
>    remove() callback,
> 2. Sets work struct with devm_work_autocancel(),
> 3. Registers interrupt handler with devm_request_threaded_irq().
> 
> Which leads to following unbind/removal path:
> 
> 1. destroy_workqueue() via driver remove(),
>    Any interrupt coming now would still execute the interrupt handler,
>    which queues work on destroyed workqueue.
> 2. devm_irq_release(),
> 3. devm_work_drop() -> cancel_work_sync() on destroyed workqueue.
> 
> devm_alloc_workqueue() has two benefits:
> 1. Solves above problem of mix-and-match devres and non-devres code in
>    driver,
> 2. Simplify any sane drivers which were correctly using
>    alloc_workqueue() + devm_add_action_or_reset().
> 
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>

Acked-by: Tejun Heo <tj@kernel.org>

Please let me know how you wanna route the patch.

Thanks.

-- 
tejun