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* [PATCH] ASoC: atmel_ssc_dai: Remove wrong spinlock usage
@ 2019-09-18  9:41 Gregory CLEMENT
  2019-09-18  9:48 ` Alexandre Belloni
  0 siblings, 1 reply; 3+ messages in thread
From: Gregory CLEMENT @ 2019-09-18  9:41 UTC (permalink / raw)
  To: Codrin Ciubotariu, Liam Girdwood, Mark Brown, alsa-devel,
	linux-kernel
  Cc: Alexandre Belloni, Ludovic Desroches, linux-arm-kernel,
	Gregory CLEMENT

A potential bug was reported in the email "[BUG] atmel_ssc_dai: a
possible sleep-in-atomic bug in atmel_ssc_shutdown"[1]

Indeed in the function atmel_ssc_shutdown() free_irq() was called in a
critical section protected by spinlock.

However this spinlock is only used in atmel_ssc_shutdown() and
atmel_ssc_startup() functions. After further analysis, it occurred that
the call to these function are already protected by mutex used on the
calling functions.

Then we can remove the spinlock which will fix this bug as a side
effect. Thanks to this patch the following message disappears:

"BUG: sleeping function called from invalid context at
kernel/locking/mutex.c:909"

[1]: https://www.spinics.net/lists/alsa-devel/msg71286.html

Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
---
 sound/soc/atmel/atmel_ssc_dai.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/sound/soc/atmel/atmel_ssc_dai.c b/sound/soc/atmel/atmel_ssc_dai.c
index 6f89483ac88c..365957e86419 100644
--- a/sound/soc/atmel/atmel_ssc_dai.c
+++ b/sound/soc/atmel/atmel_ssc_dai.c
@@ -116,19 +116,16 @@ static struct atmel_pcm_dma_params ssc_dma_params[NUM_SSC_DEVICES][2] = {
 static struct atmel_ssc_info ssc_info[NUM_SSC_DEVICES] = {
 	{
 	.name		= "ssc0",
-	.lock		= __SPIN_LOCK_UNLOCKED(ssc_info[0].lock),
 	.dir_mask	= SSC_DIR_MASK_UNUSED,
 	.initialized	= 0,
 	},
 	{
 	.name		= "ssc1",
-	.lock		= __SPIN_LOCK_UNLOCKED(ssc_info[1].lock),
 	.dir_mask	= SSC_DIR_MASK_UNUSED,
 	.initialized	= 0,
 	},
 	{
 	.name		= "ssc2",
-	.lock		= __SPIN_LOCK_UNLOCKED(ssc_info[2].lock),
 	.dir_mask	= SSC_DIR_MASK_UNUSED,
 	.initialized	= 0,
 	},
@@ -317,13 +314,11 @@ static int atmel_ssc_startup(struct snd_pcm_substream *substream,
 
 	snd_soc_dai_set_dma_data(dai, substream, dma_params);
 
-	spin_lock_irq(&ssc_p->lock);
 	if (ssc_p->dir_mask & dir_mask) {
 		spin_unlock_irq(&ssc_p->lock);
 		return -EBUSY;
 	}
 	ssc_p->dir_mask |= dir_mask;
-	spin_unlock_irq(&ssc_p->lock);
 
 	return 0;
 }
@@ -355,7 +350,6 @@ static void atmel_ssc_shutdown(struct snd_pcm_substream *substream,
 
 	dir_mask = 1 << dir;
 
-	spin_lock_irq(&ssc_p->lock);
 	ssc_p->dir_mask &= ~dir_mask;
 	if (!ssc_p->dir_mask) {
 		if (ssc_p->initialized) {
@@ -369,7 +363,6 @@ static void atmel_ssc_shutdown(struct snd_pcm_substream *substream,
 		ssc_p->cmr_div = ssc_p->tcmr_period = ssc_p->rcmr_period = 0;
 		ssc_p->forced_divider = 0;
 	}
-	spin_unlock_irq(&ssc_p->lock);
 
 	/* Shutdown the SSC clock. */
 	pr_debug("atmel_ssc_dai: Stopping clock\n");
-- 
2.23.0


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^ permalink raw reply related	[flat|nested] 3+ messages in thread
* Re: [PATCH] ASoC: atmel_ssc_dai: Remove wrong spinlock usage
  2019-09-18  9:41 [PATCH] ASoC: atmel_ssc_dai: Remove wrong spinlock usage Gregory CLEMENT
@ 2019-09-18  9:48 ` Alexandre Belloni
  2019-09-18  9:59   ` Gregory CLEMENT
  0 siblings, 1 reply; 3+ messages in thread
From: Alexandre Belloni @ 2019-09-18  9:48 UTC (permalink / raw)
  To: Gregory CLEMENT
  Cc: alsa-devel, linux-kernel, Liam Girdwood, Ludovic Desroches,
	Mark Brown, Codrin Ciubotariu, linux-arm-kernel

On 18/09/2019 11:41:14+0200, Gregory CLEMENT wrote:
> A potential bug was reported in the email "[BUG] atmel_ssc_dai: a
> possible sleep-in-atomic bug in atmel_ssc_shutdown"[1]
> 
> Indeed in the function atmel_ssc_shutdown() free_irq() was called in a
> critical section protected by spinlock.
> 
> However this spinlock is only used in atmel_ssc_shutdown() and
> atmel_ssc_startup() functions. After further analysis, it occurred that
> the call to these function are already protected by mutex used on the
> calling functions.
> 
> Then we can remove the spinlock which will fix this bug as a side
> effect. Thanks to this patch the following message disappears:
> 
> "BUG: sleeping function called from invalid context at
> kernel/locking/mutex.c:909"
> 
> [1]: https://www.spinics.net/lists/alsa-devel/msg71286.html
> 
> Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
> ---
>  sound/soc/atmel/atmel_ssc_dai.c | 7 -------
>  1 file changed, 7 deletions(-)
> 
> diff --git a/sound/soc/atmel/atmel_ssc_dai.c b/sound/soc/atmel/atmel_ssc_dai.c
> index 6f89483ac88c..365957e86419 100644
> --- a/sound/soc/atmel/atmel_ssc_dai.c
> +++ b/sound/soc/atmel/atmel_ssc_dai.c
> @@ -116,19 +116,16 @@ static struct atmel_pcm_dma_params ssc_dma_params[NUM_SSC_DEVICES][2] = {
>  static struct atmel_ssc_info ssc_info[NUM_SSC_DEVICES] = {
>  	{
>  	.name		= "ssc0",
> -	.lock		= __SPIN_LOCK_UNLOCKED(ssc_info[0].lock),

This member is now unused and can be removed from the struct.

Once fixed, Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

>  	.dir_mask	= SSC_DIR_MASK_UNUSED,
>  	.initialized	= 0,
>  	},
>  	{
>  	.name		= "ssc1",
> -	.lock		= __SPIN_LOCK_UNLOCKED(ssc_info[1].lock),
>  	.dir_mask	= SSC_DIR_MASK_UNUSED,
>  	.initialized	= 0,
>  	},
>  	{
>  	.name		= "ssc2",
> -	.lock		= __SPIN_LOCK_UNLOCKED(ssc_info[2].lock),
>  	.dir_mask	= SSC_DIR_MASK_UNUSED,
>  	.initialized	= 0,
>  	},
> @@ -317,13 +314,11 @@ static int atmel_ssc_startup(struct snd_pcm_substream *substream,
>  
>  	snd_soc_dai_set_dma_data(dai, substream, dma_params);
>  
> -	spin_lock_irq(&ssc_p->lock);
>  	if (ssc_p->dir_mask & dir_mask) {
>  		spin_unlock_irq(&ssc_p->lock);
>  		return -EBUSY;
>  	}
>  	ssc_p->dir_mask |= dir_mask;
> -	spin_unlock_irq(&ssc_p->lock);
>  
>  	return 0;
>  }
> @@ -355,7 +350,6 @@ static void atmel_ssc_shutdown(struct snd_pcm_substream *substream,
>  
>  	dir_mask = 1 << dir;
>  
> -	spin_lock_irq(&ssc_p->lock);
>  	ssc_p->dir_mask &= ~dir_mask;
>  	if (!ssc_p->dir_mask) {
>  		if (ssc_p->initialized) {
> @@ -369,7 +363,6 @@ static void atmel_ssc_shutdown(struct snd_pcm_substream *substream,
>  		ssc_p->cmr_div = ssc_p->tcmr_period = ssc_p->rcmr_period = 0;
>  		ssc_p->forced_divider = 0;
>  	}
> -	spin_unlock_irq(&ssc_p->lock);
>  
>  	/* Shutdown the SSC clock. */
>  	pr_debug("atmel_ssc_dai: Stopping clock\n");
> -- 
> 2.23.0
> 

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply	[flat|nested] 3+ messages in thread
* Re: [PATCH] ASoC: atmel_ssc_dai: Remove wrong spinlock usage
  2019-09-18  9:48 ` Alexandre Belloni
@ 2019-09-18  9:59   ` Gregory CLEMENT
  0 siblings, 0 replies; 3+ messages in thread
From: Gregory CLEMENT @ 2019-09-18  9:59 UTC (permalink / raw)
  To: Alexandre Belloni
  Cc: alsa-devel, linux-kernel, Liam Girdwood, Ludovic Desroches,
	Mark Brown, Codrin Ciubotariu, linux-arm-kernel

Hi Alex,

> On 18/09/2019 11:41:14+0200, Gregory CLEMENT wrote:
>> A potential bug was reported in the email "[BUG] atmel_ssc_dai: a
>> possible sleep-in-atomic bug in atmel_ssc_shutdown"[1]
>> 
>> Indeed in the function atmel_ssc_shutdown() free_irq() was called in a
>> critical section protected by spinlock.
>> 
>> However this spinlock is only used in atmel_ssc_shutdown() and
>> atmel_ssc_startup() functions. After further analysis, it occurred that
>> the call to these function are already protected by mutex used on the
>> calling functions.
>> 
>> Then we can remove the spinlock which will fix this bug as a side
>> effect. Thanks to this patch the following message disappears:
>> 
>> "BUG: sleeping function called from invalid context at
>> kernel/locking/mutex.c:909"
>> 
>> [1]: https://www.spinics.net/lists/alsa-devel/msg71286.html
>> 
>> Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
>> ---
>>  sound/soc/atmel/atmel_ssc_dai.c | 7 -------
>>  1 file changed, 7 deletions(-)
>> 
>> diff --git a/sound/soc/atmel/atmel_ssc_dai.c b/sound/soc/atmel/atmel_ssc_dai.c
>> index 6f89483ac88c..365957e86419 100644
>> --- a/sound/soc/atmel/atmel_ssc_dai.c
>> +++ b/sound/soc/atmel/atmel_ssc_dai.c
>> @@ -116,19 +116,16 @@ static struct atmel_pcm_dma_params ssc_dma_params[NUM_SSC_DEVICES][2] = {
>>  static struct atmel_ssc_info ssc_info[NUM_SSC_DEVICES] = {
>>  	{
>>  	.name		= "ssc0",
>> -	.lock		= __SPIN_LOCK_UNLOCKED(ssc_info[0].lock),
>
> This member is now unused and can be removed from the struct.
>
> Once fixed, Reviewed-by: Alexandre Belloni
> <alexandre.belloni@bootlin.com>

Indeed I wanted to do this but finally forgot.
I am sending a v2.

Thanks,

Gregory

>
>>  	.dir_mask	= SSC_DIR_MASK_UNUSED,
>>  	.initialized	= 0,
>>  	},
>>  	{
>>  	.name		= "ssc1",
>> -	.lock		= __SPIN_LOCK_UNLOCKED(ssc_info[1].lock),
>>  	.dir_mask	= SSC_DIR_MASK_UNUSED,
>>  	.initialized	= 0,
>>  	},
>>  	{
>>  	.name		= "ssc2",
>> -	.lock		= __SPIN_LOCK_UNLOCKED(ssc_info[2].lock),
>>  	.dir_mask	= SSC_DIR_MASK_UNUSED,
>>  	.initialized	= 0,
>>  	},
>> @@ -317,13 +314,11 @@ static int atmel_ssc_startup(struct snd_pcm_substream *substream,
>>  
>>  	snd_soc_dai_set_dma_data(dai, substream, dma_params);
>>  
>> -	spin_lock_irq(&ssc_p->lock);
>>  	if (ssc_p->dir_mask & dir_mask) {
>>  		spin_unlock_irq(&ssc_p->lock);
>>  		return -EBUSY;
>>  	}
>>  	ssc_p->dir_mask |= dir_mask;
>> -	spin_unlock_irq(&ssc_p->lock);
>>  
>>  	return 0;
>>  }
>> @@ -355,7 +350,6 @@ static void atmel_ssc_shutdown(struct snd_pcm_substream *substream,
>>  
>>  	dir_mask = 1 << dir;
>>  
>> -	spin_lock_irq(&ssc_p->lock);
>>  	ssc_p->dir_mask &= ~dir_mask;
>>  	if (!ssc_p->dir_mask) {
>>  		if (ssc_p->initialized) {
>> @@ -369,7 +363,6 @@ static void atmel_ssc_shutdown(struct snd_pcm_substream *substream,
>>  		ssc_p->cmr_div = ssc_p->tcmr_period = ssc_p->rcmr_period = 0;
>>  		ssc_p->forced_divider = 0;
>>  	}
>> -	spin_unlock_irq(&ssc_p->lock);
>>  
>>  	/* Shutdown the SSC clock. */
>>  	pr_debug("atmel_ssc_dai: Stopping clock\n");
>> -- 
>> 2.23.0
>> 
>
> -- 
> Alexandre Belloni, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com

-- 
Gregory Clement, Bootlin
Embedded Linux and Kernel engineering
http://bootlin.com

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply	[flat|nested] 3+ messages in thread
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2019-09-18  9:41 [PATCH] ASoC: atmel_ssc_dai: Remove wrong spinlock usage Gregory CLEMENT
2019-09-18  9:48 ` Alexandre Belloni
2019-09-18  9:59   ` Gregory CLEMENT

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