Re: [PATCH 2/5] dmaengine: virt-dma: Do not call desc_free() under a spin_lock

[Sascha Hauer <s.hauer@pengutronix.de>]

On Mon, Dec 09, 2019 at 09:48:22AM +0200, Peter Ujfalusi wrote:
> Hi Sascha,
> 
> 
> On 06/12/2019 15.53, Sascha Hauer wrote:
> > vchan_vdesc_fini() shouldn't be called under a spin_lock. This is done
> > in two places, once in vchan_terminate_vdesc() and once in
> > vchan_synchronize(). Instead of freeing the vdesc right away, collect
> > the aborted vdescs on a separate list and free them along with the other
> > vdescs.
> > 
> > Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> > ---
> >  drivers/dma/virt-dma.c |  1 +
> >  drivers/dma/virt-dma.h | 17 +++--------------
> >  2 files changed, 4 insertions(+), 14 deletions(-)
> > 
> > diff --git a/drivers/dma/virt-dma.c b/drivers/dma/virt-dma.c
> > index ec4adf4260a0..87d5bd53c98b 100644
> > --- a/drivers/dma/virt-dma.c
> > +++ b/drivers/dma/virt-dma.c
> > @@ -135,6 +135,7 @@ void vchan_init(struct virt_dma_chan *vc, struct dma_device *dmadev)
> >  	INIT_LIST_HEAD(&vc->desc_submitted);
> >  	INIT_LIST_HEAD(&vc->desc_issued);
> >  	INIT_LIST_HEAD(&vc->desc_completed);
> > +	INIT_LIST_HEAD(&vc->desc_aborted);
> 
> Can we keep the terminated term instead of aborted: desc_terminated

Sure.

> >  	tasklet_kill(&vc->task);
> > -
> > -	spin_lock_irqsave(&vc->lock, flags);
> > -	if (vc->vd_terminated) {
> > -		vchan_vdesc_fini(vc->vd_terminated);
> > -		vc->vd_terminated = NULL;
> > -	}
> > -	spin_unlock_irqrestore(&vc->lock, flags);
> 
> We don't want the terminated descriptors to accumulate until the channel
> is freed up.

Nothing easier than that. I just have to revert to an earlier version
before I decided that it's better to free up the descriptors at the end ;)

I'll send a v2 shortly.

Sascha


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