Re: [RFC PATCH 01/12] workqueue: Add interface to teach lockdep to warn on reclaim violations

Tejun Heo
2026-03-25T15:59:58Z

Sorry about the tardiness. Traveling during spring break. Getting more than
I can catch up with each day.

On Sun, Mar 15, 2026 at 09:32:44PM -0700, Matthew Brost wrote:
> @@ -403,6 +403,7 @@ enum wq_flags {
> */
> WQ_POWER_EFFICIENT = 1 << 7,
> WQ_PERCPU = 1 << 8, /* bound to a specific cpu */
> + WQ_MEM_WARN_ON_RECLAIM = 1 << 9, /* teach lockdep to warn on reclaim */

Shouldn't this require WQ_MEM_RECLAIM?

> +/**
> + * workqueue_is_reclaim_annotated() - Test whether a workqueue is annotated for
> + * reclaim safety
> + * @wq: workqueue to test
> + *
> + * Returns true if @wq is flags have both %WQ_MEM_WARN_ON_RECLAIM and
> + * %WQ_MEM_RECLAIM set. A workqueue marked with these flags indicates that it
> + * participates in reclaim paths, and therefore must not perform memory
> + * allocations that can recurse into reclaim (e.g., GFP_KERNEL is not allowed).
> + *
> + * Drivers can use this helper to enforce reclaim-safe behavior on workqueues
> + * that are created or provided elsewhere in the code.
> + *
> + * Return:
> + * true if the workqueue is reclaim-annotated, false otherwise.
> + */
> +bool workqueue_is_reclaim_annotated(struct workqueue_struct *wq)
> +{
> + return (wq->flags & WQ_MEM_WARN_ON_RECLAIM) &&
> + (wq->flags & WQ_MEM_RECLAIM);
> +}
> +EXPORT_SYMBOL_GPL(workqueue_is_reclaim_annotated);

Why is this function necessary? It feels rather odd to use wq as the source
of this information. Shouldn't that be an innate knowledge of the code
that's using this?

Thanks.

--
tejun