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

[Romanowski, Rafal]

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@xxxxxxxxxx> On Behalf Of
> Wander Lairson Costa
> Sent: Wednesday, December 4, 2024 12:42 PM
> To: Nguyen, Anthony L <anthony.l.nguyen@xxxxxxxxx>; Kitszel, Przemyslaw
> <przemyslaw.kitszel@xxxxxxxxx>; Andrew Lunn <andrew+netdev@xxxxxxx>;
> David S. Miller <davem@xxxxxxxxxxxxx>; Eric Dumazet
> <edumazet@xxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>; Paolo Abeni
> <pabeni@xxxxxxxxxx>; Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>; Clark
> Williams <clrkwllms@xxxxxxxxxx>; Steven Rostedt <rostedt@xxxxxxxxxxx>; Auke
> Kok <auke-jan.h.kok@xxxxxxxxx>; Jeff Garzik <jgarzik@xxxxxxxxxx>; moderated
> list:INTEL ETHERNET DRIVERS <intel-wired-lan@xxxxxxxxxxxxxxxx>; open
> list:NETWORKING DRIVERS <netdev@xxxxxxxxxxxxxxx>; open list <linux-
> kernel@xxxxxxxxxxxxxxx>; open list:Real-time Linux
> (PREEMPT_RT):Keyword:PREEMPT_RT <linux-rt-devel@xxxxxxxxxxxxxxx>
> Cc: Wander Lairson Costa <wander@xxxxxxxxxx>
> 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@xxxxxxxxxx>
> ---
>  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@xxxxxxxxx>