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

[Peter Ujfalusi <peter.ujfalusi@ti.com>]

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

>  
>  	tasklet_init(&vc->task, vchan_complete, (unsigned long)vc);
>  
> diff --git a/drivers/dma/virt-dma.h b/drivers/dma/virt-dma.h
> index 41883ee2c29f..6cae93624f0d 100644
> --- a/drivers/dma/virt-dma.h
> +++ b/drivers/dma/virt-dma.h
> @@ -31,9 +31,9 @@ struct virt_dma_chan {
>  	struct list_head desc_submitted;
>  	struct list_head desc_issued;
>  	struct list_head desc_completed;
> +	struct list_head desc_aborted;
>  
>  	struct virt_dma_desc *cyclic;
> -	struct virt_dma_desc *vd_terminated;
>  };
>  
>  static inline struct virt_dma_chan *to_virt_chan(struct dma_chan *chan)
> @@ -146,11 +146,8 @@ static inline void vchan_terminate_vdesc(struct virt_dma_desc *vd)
>  {
>  	struct virt_dma_chan *vc = to_virt_chan(vd->tx.chan);
>  
> -	/* free up stuck descriptor */
> -	if (vc->vd_terminated)
> -		vchan_vdesc_fini(vc->vd_terminated);
> +	list_add_tail(&vd->node, &vc->desc_aborted);
>  
> -	vc->vd_terminated = vd;
>  	if (vc->cyclic == vd)
>  		vc->cyclic = NULL;
>  }
> @@ -184,6 +181,7 @@ static inline void vchan_get_all_descriptors(struct virt_dma_chan *vc,
>  	list_splice_tail_init(&vc->desc_submitted, head);
>  	list_splice_tail_init(&vc->desc_issued, head);
>  	list_splice_tail_init(&vc->desc_completed, head);
> +	list_splice_tail_init(&vc->desc_aborted, head);
>  }
>  
>  static inline void vchan_free_chan_resources(struct virt_dma_chan *vc)
> @@ -212,16 +210,7 @@ static inline void vchan_free_chan_resources(struct virt_dma_chan *vc)
>   */
>  static inline void vchan_synchronize(struct virt_dma_chan *vc)
>  {
> -	unsigned long flags;
> -
>  	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.

spin_lock_irqsave(&vc->lock, flags);
list_splice_tail_init(&vc->desc_terminated, &head);
spin_unlock_irqrestore(&vc->lock, flags);

list_for_each_entry_safe(vd, _vd, &head, node) {
	list_del(&vd->node);
	vchan_vdesc_fini(vd);
}


>  }
>  
>  #endif
> 

- Péter

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