netdev - [PATCH iwl-net 1/4] igb: narrow scope of vfs

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Message-ID: <20241204114229.21452-2-wander@redhat.com>
Date: Wed,  4 Dec 2024 08:42:24 -0300
From: Wander Lairson Costa <wander@...hat.com>
To: Tony Nguyen <anthony.l.nguyen@...el.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Clark Williams <clrkwllms@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Auke Kok <auke-jan.h.kok@...el.com>,
	Jeff Garzik <jgarzik@...hat.com>,
	intel-wired-lan@...ts.osuosl.org (moderated list:INTEL ETHERNET DRIVERS),
	netdev@...r.kernel.org (open list:NETWORKING DRIVERS),
	linux-kernel@...r.kernel.org (open list),
	linux-rt-devel@...ts.linux.dev (open list:Real-time Linux (PREEMPT_RT):Keyword:PREEMPT_RT)
Cc: Wander Lairson Costa <wander@...hat.com>
Subject: [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@...hat.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