RE: [Intel-wired-lan] [PATCH iwl-net 1/4] igb: narrow scope of vfs_lock in SR-IOV cleanup

-----Original Message-----
From: Intel-wired-lan <redacted> 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
[off-list ref]; Andrew Lunn [off-list ref];
David S. Miller [off-list ref]; Eric Dumazet
[off-list ref]; Jakub Kicinski [off-list ref]; Paolo Abeni
[off-list ref]; Sebastian Andrzej Siewior [off-list ref]; Clark
Williams [off-list ref]; Steven Rostedt [off-list ref]; Auke
Kok [off-list ref]; Jeff Garzik [off-list ref]; moderated
list:INTEL ETHERNET DRIVERS [off-list ref]; open
list:NETWORKING DRIVERS [off-list ref]; open list <linux-
kernel@vger.kernel.org>; open list:Real-time Linux
(PREEMPT_RT):Keyword:PREEMPT_RT [off-list ref]
Cc: Wander Lairson Costa <redacted>
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 <redacted>
---
 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,