Re: [PATCH] ibmvnic: remove excessive irqsave

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);