Re: [PATCH] ibmvnic: remove excessive irqsave

[Lijun Pan]

> On Mar 4, 2021, at 11:49 PM, Christophe Leroy <christophe.leroy@xxxxxxxxxx> wrote:
> 
> 
> 
> Le 05/03/2021 à 02:43, angkery a écrit :
>> From: Junlin Yang <yangjunlin@xxxxxxxxxx>
>> 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@xxxxxxxxxx>
>> ---
>>  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);
>>