The adapter->vfs_lock currently protects critical sections shared between
igb_disable_sriov() and igb_msg_task(). Since igb_msg_task() — which is
invoked solely by the igb_msix_other() ISR—only proceeds when
adapter->vfs_allocated_count > 0, we can reduce the lock scope further.

By moving the assignment adapter->vfs_allocated_count = 0 to the start of the
cleanup code in igb_disable_sriov(), we can restrict the spinlock protection
solely to this assignment. This change removes kfree() calls from within the
locked section, simplifying lock management.

Once kfree() is outside the vfs_lock scope, it becomes possible to safely
convert vfs_lock to a raw_spin_lock.

Signed-off-by: Wander Lairson Costa <wander@redhat.com>
---
 drivers/net/ethernet/intel/igb/igb_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index 08578980b6518..4ca25660e876e 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -3708,12 +3708,12 @@ static int igb_disable_sriov(struct pci_dev *pdev, bool reinit)
 			msleep(500);
 		}
 		spin_lock_irqsave(&adapter->vfs_lock, flags);
+		adapter->vfs_allocated_count = 0;
+		spin_unlock_irqrestore(&adapter->vfs_lock, flags);
 		kfree(adapter->vf_mac_list);
 		adapter->vf_mac_list = NULL;
 		kfree(adapter->vf_data);
 		adapter->vf_data = NULL;
-		adapter->vfs_allocated_count = 0;
-		spin_unlock_irqrestore(&adapter->vfs_lock, flags);
 		wr32(E1000_IOVCTL, E1000_IOVCTL_REUSE_VFQ);
 		wrfl();
 		msleep(100);
-- 
2.47.0

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@osuosl.org> On Behalf Of
> Wander Lairson Costa
> Sent: Wednesday, December 4, 2024 12:42 PM
> To: Nguyen, Anthony L <anthony.l.nguyen@intel.com>; Kitszel, Przemyslaw
> <przemyslaw.kitszel@intel.com>; Andrew Lunn <andrew+netdev@lunn.ch>;
> David S. Miller <davem@davemloft.net>; Eric Dumazet
> <edumazet@google.com>; Jakub Kicinski <kuba@kernel.org>; Paolo Abeni
> <pabeni@redhat.com>; Sebastian Andrzej Siewior <bigeasy@linutronix.de>; Clark
> Williams <clrkwllms@kernel.org>; Steven Rostedt <rostedt@goodmis.org>; Auke
> Kok <auke-jan.h.kok@intel.com>; Jeff Garzik <jgarzik@redhat.com>; moderated
> list:INTEL ETHERNET DRIVERS <intel-wired-lan@lists.osuosl.org>; open
> list:NETWORKING DRIVERS <netdev@vger.kernel.org>; open list <linux-
> kernel@vger.kernel.org>; open list:Real-time Linux
> (PREEMPT_RT):Keyword:PREEMPT_RT <linux-rt-devel@lists.linux.dev>
> Cc: Wander Lairson Costa <wander@redhat.com>
> Subject: [Intel-wired-lan] [PATCH iwl-net 1/4] igb: narrow scope of vfs_lock in SR-
> IOV cleanup
> 
> The adapter->vfs_lock currently protects critical sections shared between
> igb_disable_sriov() and igb_msg_task(). Since igb_msg_task() — which is invoked
> solely by the igb_msix_other() ISR—only proceeds when
> adapter->vfs_allocated_count > 0, we can reduce the lock scope further.
> 
> By moving the assignment adapter->vfs_allocated_count = 0 to the start of the
> cleanup code in igb_disable_sriov(), we can restrict the spinlock protection solely
> to this assignment. This change removes kfree() calls from within the locked
> section, simplifying lock management.
> 
> Once kfree() is outside the vfs_lock scope, it becomes possible to safely convert
> vfs_lock to a raw_spin_lock.
> 
> Signed-off-by: Wander Lairson Costa <wander@redhat.com>
> ---
>  drivers/net/ethernet/intel/igb/igb_main.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c
> b/drivers/net/ethernet/intel/igb/igb_main.c
> index 08578980b6518..4ca25660e876e 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -3708,12 +3708,12 @@ static int igb_disable_sriov(struct pci_dev *pdev,

Tested-by: Rafal Romanowski <rafal.romanowski@intel.com>