linux-kernel - Re: [PATCH] dmaengine: xgene-dma: Fix holding lock while calling tx callback in cleanup path

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Date:	Fri, 21 Aug 2015 14:15:08 +0530
From:	Rameshwar Sahu <rsahu@....com>
To:	Vinod Koul <vinod.koul@...el.com>
Cc:	dan.j.williams@...el.com, dmaengine@...r.kernel.org,
	Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	jcm@...hat.com, patches@....com
Subject: Re: [PATCH] dmaengine: xgene-dma: Fix holding lock while calling tx
 callback in cleanup path

Hi Vinod,

On Fri, Aug 21, 2015 at 2:09 PM, Vinod Koul <vinod.koul@...el.com> wrote:
> On Thu, Aug 20, 2015 at 04:00:56PM +0530, Rameshwar Prasad Sahu wrote:
>> This patch fixes the an locking issue where client callback performs
>                 ^^^^^^^^^^^^
> ??
>
>> further submission.
> Do you men you are preventing that or fixing for this to be allowed?

Fixing lock to allow client to submit further request in there
callback routine if they would like.
>
>>
>> Signed-off-by: Rameshwar Prasad Sahu <rsahu@....com>
>> ---
>>  drivers/dma/xgene-dma.c | 33 ++++++++++++++++++++++-----------
>>  1 file changed, 22 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/dma/xgene-dma.c b/drivers/dma/xgene-dma.c
>> index d1c8809..0b82bc0 100644
>> --- a/drivers/dma/xgene-dma.c
>> +++ b/drivers/dma/xgene-dma.c
>> @@ -763,12 +763,17 @@ static void xgene_dma_cleanup_descriptors(struct xgene_dma_chan *chan)
>>       struct xgene_dma_ring *ring = &chan->rx_ring;
>>       struct xgene_dma_desc_sw *desc_sw, *_desc_sw;
>>       struct xgene_dma_desc_hw *desc_hw;
>> +     struct list_head ld_completed;
>>       u8 status;
>>
>> +     INIT_LIST_HEAD(&ld_completed);
>> +
>> +     spin_lock_bh(&chan->lock);
>> +
>>       /* Clean already completed and acked descriptors */
>>       xgene_dma_clean_completed_descriptor(chan);
>>
>> -     /* Run the callback for each descriptor, in order */
>> +     /* Move all completed descriptors to ld completed queue, in order */
>>       list_for_each_entry_safe(desc_sw, _desc_sw, &chan->ld_running, node) {
>>               /* Get subsequent hw descriptor from DMA rx ring */
>>               desc_hw = &ring->desc_hw[ring->head];
>> @@ -811,15 +816,17 @@ static void xgene_dma_cleanup_descriptors(struct xgene_dma_chan *chan)
>>               /* Mark this hw descriptor as processed */
>>               desc_hw->m0 = cpu_to_le64(XGENE_DMA_DESC_EMPTY_SIGNATURE);
>>
>> -             xgene_dma_run_tx_complete_actions(chan, desc_sw);
>> -
>> -             xgene_dma_clean_running_descriptor(chan, desc_sw);
>> -
>>               /*
>>                * Decrement the pending transaction count
>>                * as we have processed one
>>                */
>>               chan->pending--;
>> +
>> +             /*
>> +              * Delete this node from ld running queue and append it to
>> +              * ld completed queue for further processing
>> +              */
>> +             list_move_tail(&desc_sw->node, &ld_completed);
>>       }
>>
>>       /*
>> @@ -828,6 +835,14 @@ static void xgene_dma_cleanup_descriptors(struct xgene_dma_chan *chan)
>>        * ahead and free the descriptors below.
>>        */
>>       xgene_chan_xfer_ld_pending(chan);
>> +
>> +     spin_unlock_bh(&chan->lock);
>> +
>> +     /* Run the callback for each descriptor, in order */
>> +     list_for_each_entry_safe(desc_sw, _desc_sw, &ld_completed, node) {
>> +             xgene_dma_run_tx_complete_actions(chan, desc_sw);
>> +             xgene_dma_clean_running_descriptor(chan, desc_sw);
>> +     }
>>  }
>>
>>  static int xgene_dma_alloc_chan_resources(struct dma_chan *dchan)
>> @@ -876,11 +891,11 @@ static void xgene_dma_free_chan_resources(struct dma_chan *dchan)
>>       if (!chan->desc_pool)
>>               return;
>>
>> -     spin_lock_bh(&chan->lock);
>> -
>>       /* Process all running descriptor */
>>       xgene_dma_cleanup_descriptors(chan);
>>
>> +     spin_lock_bh(&chan->lock);
>> +
>>       /* Clean all link descriptor queues */
>>       xgene_dma_free_desc_list(chan, &chan->ld_pending);
>>       xgene_dma_free_desc_list(chan, &chan->ld_running);
>> @@ -1200,15 +1215,11 @@ static void xgene_dma_tasklet_cb(unsigned long data)
>>  {
>>       struct xgene_dma_chan *chan = (struct xgene_dma_chan *)data;
>>
>> -     spin_lock_bh(&chan->lock);
>> -
>>       /* Run all cleanup for descriptors which have been completed */
>>       xgene_dma_cleanup_descriptors(chan);
>>
>>       /* Re-enable DMA channel IRQ */
>>       enable_irq(chan->rx_irq);
>> -
>> -     spin_unlock_bh(&chan->lock);
>>  }
>>
>>  static irqreturn_t xgene_dma_chan_ring_isr(int irq, void *id)
>> --
>> 1.8.2.1
>>
>
> --
> ~Vinod
--
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