linux-kernel - Re: [PATCH 2/9] dma: Convert from tasklet to BH workqueue

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Message-ID: <CACRpkdaSBGe0EFm1gK-7qPK4e6T2H1dxFXjhJqO2hWCm1-bNdA@mail.gmail.com>
Date: Tue, 2 Apr 2024 14:25:15 +0200
From: Linus Walleij <linus.walleij@...aro.org>
To: Allen Pais <apais@...ux.microsoft.com>
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Subject: Re: [PATCH 2/9] dma: Convert from tasklet to BH workqueue

Hi Allen,

thanks for your patch!

On Wed, Mar 27, 2024 at 5:03 PM Allen Pais <apais@...ux.microsoft.com> wrote:

> The only generic interface to execute asynchronously in the BH context is
> tasklet; however, it's marked deprecated and has some design flaws. To
> replace tasklets, BH workqueue support was recently added. A BH workqueue
> behaves similarly to regular workqueues except that the queued work items
> are executed in the BH context.
>
> This patch converts drivers/dma/* from tasklet to BH workqueue.
>
> Based on the work done by Tejun Heo <tj@...nel.org>
> Branch: git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git for-6.10
>
> Signed-off-by: Allen Pais <allen.lkml@...il.com>
(...)
> diff --git a/drivers/dma/ste_dma40.c b/drivers/dma/ste_dma40.c
(...)
>         if (d40c->pending_tx)
> -               tasklet_schedule(&d40c->tasklet);
> +               queue_work(system_bh_wq, &d40c->work);

Why is "my" driver not allowed to use system_bh_highpri_wq?

I can't see the reasoning between some drivers using system_bh_wq
and others being highpri?

Given the DMA usecase I would expect them all to be high prio.

Yours,
Linus Walleij