[PATCH] ibmvnic: remove excessive irqsave

[PATCH] ibmvnic: remove excessive irqsave

[angkery]

From: Junlin Yang <yangjunlin@yulong.com>

ibmvnic_remove locks multiple spinlocks while disabling interrupts:
spin_lock_irqsave(&adapter->state_lock, flags);
spin_lock_irqsave(&adapter->rwi_lock, flags);

there is no need for the second irqsave,since interrupts are disabled
at that point, so remove the second irqsave:
spin_lock_irqsave(&adapter->state_lock, flags);
spin_lock(&adapter->rwi_lock);

Generated by: ./scripts/coccinelle/locks/flags.cocci
./drivers/net/ethernet/ibm/ibmvnic.c:5413:1-18:
ERROR: nested lock+irqsave that reuses flags from line 5404.

Signed-off-by: Junlin Yang <yangjunlin@yulong.com>
---
 drivers/net/ethernet/ibm/ibmvnic.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index 2464c8a..a52668d 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -5408,9 +5408,9 @@ static void ibmvnic_remove(struct vio_dev *dev)
 	 * after setting state, so __ibmvnic_reset() which is called
 	 * from the flush_work() below, can make progress.
 	 */
-	spin_lock_irqsave(&adapter->rwi_lock, flags);
+	spin_lock(&adapter->rwi_lock);
 	adapter->state = VNIC_REMOVING;
-	spin_unlock_irqrestore(&adapter->rwi_lock, flags);
+	spin_unlock(&adapter->rwi_lock);
 
 	spin_unlock_irqrestore(&adapter->state_lock, flags);
 
-- 
1.9.1

Re: [PATCH] ibmvnic: remove excessive irqsave

[Sukadev Bhattiprolu]

angkery [angkery@163.com] wrote:
> From: Junlin Yang <yangjunlin@yulong.com>
> 
> ibmvnic_remove locks multiple spinlocks while disabling interrupts:
> spin_lock_irqsave(&adapter->state_lock, flags);
> spin_lock_irqsave(&adapter->rwi_lock, flags);
> 
> there is no need for the second irqsave,since interrupts are disabled
> at that point, so remove the second irqsave:
> spin_lock_irqsave(&adapter->state_lock, flags);
> spin_lock(&adapter->rwi_lock);
> 
> Generated by: ./scripts/coccinelle/locks/flags.cocci
> ./drivers/net/ethernet/ibm/ibmvnic.c:5413:1-18:
> ERROR: nested lock+irqsave that reuses flags from line 5404.
> 

Thanks. Please add

Fixes: 4a41c421f367 ("ibmvnic: serialize access to work queue on remove")

> Signed-off-by: Junlin Yang <yangjunlin@yulong.com>

Reviewed-by: Sukadev Bhattiprolu <sukadev@linux.ibm.com>

Re: [PATCH] ibmvnic: remove excessive irqsave

[Christophe Leroy]

Le 05/03/2021 à 02:43, angkery a écrit :
> From: Junlin Yang <yangjunlin@yulong.com>
> 
> ibmvnic_remove locks multiple spinlocks while disabling interrupts:
> spin_lock_irqsave(&adapter->state_lock, flags);
> spin_lock_irqsave(&adapter->rwi_lock, flags);
> 
> there is no need for the second irqsave,since interrupts are disabled
> at that point, so remove the second irqsave:

The problème is not that there is no need. The problem is a lot more serious:
As reported by coccinella, the second _irqsave() overwrites the value saved in 'flags' by the first 
_irqsave, therefore when the second _irqrestore comes, the value in 'flags' is not valid, the value 
saved by the first _irqsave has been lost. This likely leads to IRQs remaining disabled, which is 
_THE_ problem really.

> spin_lock_irqsave(&adapter->state_lock, flags);
> spin_lock(&adapter->rwi_lock);
> 
> Generated by: ./scripts/coccinelle/locks/flags.cocci
> ./drivers/net/ethernet/ibm/ibmvnic.c:5413:1-18:
> ERROR: nested lock+irqsave that reuses flags from line 5404.
> 
> Signed-off-by: Junlin Yang <yangjunlin@yulong.com>
> ---
>   drivers/net/ethernet/ibm/ibmvnic.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
> index 2464c8a..a52668d 100644
> --- a/drivers/net/ethernet/ibm/ibmvnic.c
> +++ b/drivers/net/ethernet/ibm/ibmvnic.c
> @@ -5408,9 +5408,9 @@ static void ibmvnic_remove(struct vio_dev *dev)
>   	 * after setting state, so __ibmvnic_reset() which is called
>   	 * from the flush_work() below, can make progress.
>   	 */
> -	spin_lock_irqsave(&adapter->rwi_lock, flags);
> +	spin_lock(&adapter->rwi_lock);
>   	adapter->state = VNIC_REMOVING;
> -	spin_unlock_irqrestore(&adapter->rwi_lock, flags);
> +	spin_unlock(&adapter->rwi_lock);
>   
>   	spin_unlock_irqrestore(&adapter->state_lock, flags);
>   
> 

Re: [PATCH] ibmvnic: remove excessive irqsave

[Lijun Pan]

> On Mar 4, 2021, at 11:49 PM, Christophe Leroy <christophe.leroy@csgroup.eu> wrote:
> 
> 
> 
> Le 05/03/2021 à 02:43, angkery a écrit :
>> From: Junlin Yang <yangjunlin@yulong.com>
>> ibmvnic_remove locks multiple spinlocks while disabling interrupts:
>> spin_lock_irqsave(&adapter->state_lock, flags);
>> spin_lock_irqsave(&adapter->rwi_lock, flags);
>> there is no need for the second irqsave,since interrupts are disabled
>> at that point, so remove the second irqsave:
> 
> The problème is not that there is no need. The problem is a lot more serious:
> As reported by coccinella, the second _irqsave() overwrites the value saved in 'flags' by the first _irqsave, therefore when the second _irqrestore comes, the value in 'flags' is not valid, the value saved by the first _irqsave has been lost. This likely leads to IRQs remaining disabled, which is _THE_ problem really.

That does sounds like a more serious functional problem than coccinella check.
Thanks for your explanation.

> 
>> spin_lock_irqsave(&adapter->state_lock, flags);
>> spin_lock(&adapter->rwi_lock);
>> Generated by: ./scripts/coccinelle/locks/flags.cocci
>> ./drivers/net/ethernet/ibm/ibmvnic.c:5413:1-18:
>> ERROR: nested lock+irqsave that reuses flags from line 5404.
>> Signed-off-by: Junlin Yang <yangjunlin@yulong.com>
>> ---
>>  drivers/net/ethernet/ibm/ibmvnic.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>> diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
>> index 2464c8a..a52668d 100644
>> --- a/drivers/net/ethernet/ibm/ibmvnic.c
>> +++ b/drivers/net/ethernet/ibm/ibmvnic.c
>> @@ -5408,9 +5408,9 @@ static void ibmvnic_remove(struct vio_dev *dev)
>>  	 * after setting state, so __ibmvnic_reset() which is called
>>  	 * from the flush_work() below, can make progress.
>>  	 */
>> -	spin_lock_irqsave(&adapter->rwi_lock, flags);
>> +	spin_lock(&adapter->rwi_lock);
>>  	adapter->state = VNIC_REMOVING;
>> -	spin_unlock_irqrestore(&adapter->rwi_lock, flags);
>> +	spin_unlock(&adapter->rwi_lock);
>>    	spin_unlock_irqrestore(&adapter->state_lock, flags);
>>  

Re: [PATCH] ibmvnic: remove excessive irqsave

[angkery]

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On Fri, 5 Mar 2021 06:49:14 +0100
Christophe Leroy <christophe.leroy@csgroup.eu> wrote:

> Le 05/03/2021 ¨¤ 02:43, angkery a ¨¦crit0„2:
> > From: Junlin Yang <yangjunlin@yulong.com>
> > 
> > ibmvnic_remove locks multiple spinlocks while disabling interrupts:
> > spin_lock_irqsave(&adapter->state_lock, flags);
> > spin_lock_irqsave(&adapter->rwi_lock, flags);
> > 
> > there is no need for the second irqsave,since interrupts are
> > disabled at that point, so remove the second irqsave:  
> 
> The probl¨¨me is not that there is no need. The problem is a lot more
> serious: As reported by coccinella, the second _irqsave() overwrites
> the value saved in 'flags' by the first _irqsave, therefore when the
> second _irqrestore comes, the value in 'flags' is not valid, the
> value saved by the first _irqsave has been lost. This likely leads to
> IRQs remaining disabled, which is _THE_ problem really.
> 

Thank you for explaining the real problem.
I will update the commit information with your description.


> > spin_lock_irqsave(&adapter->state_lock, flags);
> > spin_lock(&adapter->rwi_lock);
> > 
> > Generated by: ./scripts/coccinelle/locks/flags.cocci
> > ./drivers/net/ethernet/ibm/ibmvnic.c:5413:1-18:
> > ERROR: nested lock+irqsave that reuses flags from line 5404.
> > 
> > Signed-off-by: Junlin Yang <yangjunlin@yulong.com>
> > ---
> >   drivers/net/ethernet/ibm/ibmvnic.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/ibm/ibmvnic.c
> > b/drivers/net/ethernet/ibm/ibmvnic.c index 2464c8a..a52668d 100644
> > --- a/drivers/net/ethernet/ibm/ibmvnic.c
> > +++ b/drivers/net/ethernet/ibm/ibmvnic.c
> > @@ -5408,9 +5408,9 @@ static void ibmvnic_remove(struct vio_dev
> > *dev)
> >   	 * after setting state, so __ibmvnic_reset() which is
> > called
> >   	 * from the flush_work() below, can make progress.
> >   	 */
> > -	spin_lock_irqsave(&adapter->rwi_lock, flags);
> > +	spin_lock(&adapter->rwi_lock);
> >   	adapter->state = VNIC_REMOVING;
> > -	spin_unlock_irqrestore(&adapter->rwi_lock, flags);
> > +	spin_unlock(&adapter->rwi_lock);
> >   
> >   	spin_unlock_irqrestore(&adapter->state_lock, flags);
> >   
> >