2015-12-23 03:09:03

by Dixit, Ashutosh

Subject: [PATCH] dma: Revert "dmaengine: mic_x100: add missing spin_unlock"

This reverts commit e958e079e254 ("dmaengine: mic_x100: add missing
spin_unlock").

The above patch is incorrect. There is nothing wrong with the original
code. The spin_lock is acquired in the "prep" functions and released
in "submit".

Signed-off-by: Ashutosh Dixit <[email protected]>
---
drivers/dma/mic_x100_dma.c | 15 +++++----------
1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/drivers/dma/mic_x100_dma.c b/drivers/dma/mic_x100_dma.c
index cddfa8d..068e920 100644
--- a/drivers/dma/mic_x100_dma.c
+++ b/drivers/dma/mic_x100_dma.c
@@ -317,7 +317,6 @@ mic_dma_prep_memcpy_lock(struct dma_chan *ch, dma_addr_t dma_dest,
struct mic_dma_chan *mic_ch = to_mic_dma_chan(ch);
struct device *dev = mic_dma_ch_to_device(mic_ch);
int result;
- struct dma_async_tx_descriptor *tx = NULL;

if (!len && !flags)
return NULL;
@@ -325,13 +324,10 @@ mic_dma_prep_memcpy_lock(struct dma_chan *ch, dma_addr_t dma_dest,
spin_lock(&mic_ch->prep_lock);
result = mic_dma_do_dma(mic_ch, flags, dma_src, dma_dest, len);
if (result >= 0)
- tx = allocate_tx(mic_ch);
-
- if (!tx)
- dev_err(dev, "Error enqueueing dma, error=%d\n", result);
-
+ return allocate_tx(mic_ch);
+ dev_err(dev, "Error enqueueing dma, error=%d\n", result);
spin_unlock(&mic_ch->prep_lock);
- return tx;
+ return NULL;
}

static struct dma_async_tx_descriptor *
@@ -339,14 +335,13 @@ mic_dma_prep_interrupt_lock(struct dma_chan *ch, unsigned long flags)
{
struct mic_dma_chan *mic_ch = to_mic_dma_chan(ch);
int ret;
- struct dma_async_tx_descriptor *tx = NULL;

spin_lock(&mic_ch->prep_lock);
ret = mic_dma_do_dma(mic_ch, flags, 0, 0, 0);
if (!ret)
- tx = allocate_tx(mic_ch);
+ return allocate_tx(mic_ch);
spin_unlock(&mic_ch->prep_lock);
- return tx;
+ return NULL;
}

/* Return the status of the transaction */
--
2.0.0.rc3.2.g998f840

2015-12-23 05:45:34

by Saurabh Sengar

Subject: Re: [PATCH] dma: Revert "dmaengine: mic_x100: add missing spin_unlock"

On 23 December 2015 at 09:05, Ashutosh Dixit <[email protected]> wrote:
> This reverts commit e958e079e254 ("dmaengine: mic_x100: add missing
> spin_unlock").
>
> The above patch is incorrect. There is nothing wrong with the original
> code. The spin_lock is acquired in the "prep" functions and released
> in "submit".

Hi Ashutosh,

If it is need to be released by submit function, we don't require the
spin_unlock on success case as well.
am I correct ?

> Signed-off-by: Ashutosh Dixit <[email protected]>
> ---
> drivers/dma/mic_x100_dma.c | 15 +++++----------
> 1 file changed, 5 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/dma/mic_x100_dma.c b/drivers/dma/mic_x100_dma.c
> index cddfa8d..068e920 100644
> --- a/drivers/dma/mic_x100_dma.c
> +++ b/drivers/dma/mic_x100_dma.c
> @@ -317,7 +317,6 @@ mic_dma_prep_memcpy_lock(struct dma_chan *ch, dma_addr_t dma_dest,
> struct mic_dma_chan *mic_ch = to_mic_dma_chan(ch);
> struct device *dev = mic_dma_ch_to_device(mic_ch);
> int result;
> - struct dma_async_tx_descriptor *tx = NULL;
>
> if (!len && !flags)
> return NULL;
> @@ -325,13 +324,10 @@ mic_dma_prep_memcpy_lock(struct dma_chan *ch, dma_addr_t dma_dest,
> spin_lock(&mic_ch->prep_lock);
> result = mic_dma_do_dma(mic_ch, flags, dma_src, dma_dest, len);
> if (result >= 0)
> - tx = allocate_tx(mic_ch);
> -
> - if (!tx)
> - dev_err(dev, "Error enqueueing dma, error=%d\n", result);
> -
> + return allocate_tx(mic_ch);
> + dev_err(dev, "Error enqueueing dma, error=%d\n", result);
> spin_unlock(&mic_ch->prep_lock);

This spin_unlock shouldn't be required as explained it is getting
released by submit function

> - return tx;
> + return NULL;
> }
>
> static struct dma_async_tx_descriptor *
> @@ -339,14 +335,13 @@ mic_dma_prep_interrupt_lock(struct dma_chan *ch, unsigned long flags)
> {
> struct mic_dma_chan *mic_ch = to_mic_dma_chan(ch);
> int ret;
> - struct dma_async_tx_descriptor *tx = NULL;
>
> spin_lock(&mic_ch->prep_lock);
> ret = mic_dma_do_dma(mic_ch, flags, 0, 0, 0);
> if (!ret)
> - tx = allocate_tx(mic_ch);
> + return allocate_tx(mic_ch);
> spin_unlock(&mic_ch->prep_lock);

and this too ?

> - return tx;
> + return NULL;
> }
>
> /* Return the status of the transaction */
> --
> 2.0.0.rc3.2.g998f840
>

2015-12-23 06:15:09

by Dixit, Ashutosh

Subject: Re: [PATCH] dma: Revert "dmaengine: mic_x100: add missing spin_unlock"

On Wed, Dec 23 2015 at 12:45:31 AM, Saurabh Sengar <[email protected]> wrote:
> On 23 December 2015 at 09:05, Ashutosh Dixit <[email protected]> wrote:
>> This reverts commit e958e079e254 ("dmaengine: mic_x100: add missing
>> spin_unlock").
>>
>> The above patch is incorrect. There is nothing wrong with the original
>> code. The spin_lock is acquired in the "prep" functions and released
>> in "submit".
>
> Hi Ashutosh,
>
> If it is need to be released by submit function, we don't require the
> spin_unlock on success case as well.
> am I correct ?

No, you are wrong. In the prep functions, we are not using spin_unlock in
success cases but in failure ones.

>> Signed-off-by: Ashutosh Dixit <[email protected]>
>> ---
>> drivers/dma/mic_x100_dma.c | 15 +++++----------
>> 1 file changed, 5 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/dma/mic_x100_dma.c b/drivers/dma/mic_x100_dma.c
>> index cddfa8d..068e920 100644
>> --- a/drivers/dma/mic_x100_dma.c
>> +++ b/drivers/dma/mic_x100_dma.c
>> @@ -317,7 +317,6 @@ mic_dma_prep_memcpy_lock(struct dma_chan *ch, dma_addr_t dma_dest,
>> struct mic_dma_chan *mic_ch = to_mic_dma_chan(ch);
>> struct device *dev = mic_dma_ch_to_device(mic_ch);
>> int result;
>> - struct dma_async_tx_descriptor *tx = NULL;
>>
>> if (!len && !flags)
>> return NULL;
>> @@ -325,13 +324,10 @@ mic_dma_prep_memcpy_lock(struct dma_chan *ch, dma_addr_t dma_dest,
>> spin_lock(&mic_ch->prep_lock);
>> result = mic_dma_do_dma(mic_ch, flags, dma_src, dma_dest, len);
>> if (result >= 0)
>> - tx = allocate_tx(mic_ch);
>> -
>> - if (!tx)
>> - dev_err(dev, "Error enqueueing dma, error=%d\n", result);
>> -
>> + return allocate_tx(mic_ch);
>> + dev_err(dev, "Error enqueueing dma, error=%d\n", result);
>> spin_unlock(&mic_ch->prep_lock);
>
> This spin_unlock shouldn't be required as explained it is getting
> released by submit function

This is a failure case. Submit will not be called in this case so
spin_unlock needs to be called here.

>> - return tx;
>> + return NULL;
>> }
>>
>> static struct dma_async_tx_descriptor *
>> @@ -339,14 +335,13 @@ mic_dma_prep_interrupt_lock(struct dma_chan *ch, unsigned long flags)
>> {
>> struct mic_dma_chan *mic_ch = to_mic_dma_chan(ch);
>> int ret;
>> - struct dma_async_tx_descriptor *tx = NULL;
>>
>> spin_lock(&mic_ch->prep_lock);
>> ret = mic_dma_do_dma(mic_ch, flags, 0, 0, 0);
>> if (!ret)
>> - tx = allocate_tx(mic_ch);
>> + return allocate_tx(mic_ch);
>> spin_unlock(&mic_ch->prep_lock);
>
> and this too ?

Yes, this too.

>> - return tx;
>> + return NULL;
>> }
>>
>> /* Return the status of the transaction */
>> --
>> 2.0.0.rc3.2.g998f840
>>