[PATCH] ibmvnic: remove excessive irqsave

From: Junlin Yang <redacted>

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 <redacted>
---
 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

angkery [angkery@163.com] wrote:

From: Junlin Yang <redacted>

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 <redacted>

Reviewed-by: Sukadev Bhattiprolu <redacted>

Le 05/03/2021 à 02:43, angkery a écrit :

From: Junlin Yang <redacted>

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.

On Mar 4, 2021, at 11:49 PM, Christophe Leroy [off-list ref] wrote:



Le 05/03/2021 à 02:43, angkery a écrit :

quoted

From: Junlin Yang <redacted>
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.

quoted

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 <redacted>
---
 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);
 

On Fri, 5 Mar 2021 06:49:14 +0100
Christophe Leroy [off-list ref] wrote:

Le 05/03/2021 à 02:43, angkery a écrit :

quoted

From: Junlin Yang <redacted>

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.

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

quoted

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 <redacted>
---
  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);