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

Vinod Koul
2024-04-02T13:11:26Z

On 02-04-24, 14:25, Linus Walleij wrote:
> Hi Allen,
>
> thanks for your patch!
>
> On Wed, Mar 27, 2024 at 5:03 PM Allen Pais <apais@linux.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@kernel.org>
> > Branch: git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git for-6.10
> >
> > Signed-off-by: Allen Pais <allen.lkml@gmail.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.

It didnt use tasklet_hi_schedule(), I guess Allen has done the
conversion of tasklet_schedule -> system_bh_wq and tasklet_hi_schedule
-> system_bh_highpri_wq

Anyway, we are going to use a dma queue so should be better performance

--
~Vinod