2019-05-07 14:30:59

by Harini Katakam

Subject: [PATCH] net: macb: Change interrupt and napi enable order in open

Current order in open:
-> Enable interrupts (macb_init_hw)
-> Enable NAPI
-> Start PHY

Sequence of RX handling:
-> RX interrupt occurs
-> Interrupt is cleared and interrupt bits disabled in handler
-> NAPI is scheduled
-> In NAPI, RX budget is processed and RX interrupts are re-enabled

With the above, on QEMU or fixed link setups (where PHY state doesn't
matter), there's a chance macb RX interrupt occurs before NAPI is
enabled. This will result in NAPI being scheduled before it is enabled.
Fix this macb open by changing the order.

Fixes: ae1f2a56d273 ("net: macb: Added support for many RX queues")
Signed-off-by: Harini Katakam <[email protected]>
---
drivers/net/ethernet/cadence/macb_main.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 5d5c9d7..c049410 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -2427,12 +2427,12 @@ static int macb_open(struct net_device *dev)
goto pm_exit;
}

- bp->macbgem_ops.mog_init_rings(bp);
- macb_init_hw(bp);
-
for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue)
napi_enable(&queue->napi);

+ bp->macbgem_ops.mog_init_rings(bp);
+ macb_init_hw(bp);
+
/* schedule a link state check */
phy_start(dev->phydev);

--
2.7.4

2019-05-07 15:35:06

by Nicolas Ferre

Subject: Re: [PATCH] net: macb: Change interrupt and napi enable order in open

On 07/05/2019 at 16:29, Harini Katakam wrote:
> External E-Mail
>
>
> Current order in open:
> -> Enable interrupts (macb_init_hw)
> -> Enable NAPI
> -> Start PHY
>
> Sequence of RX handling:
> -> RX interrupt occurs
> -> Interrupt is cleared and interrupt bits disabled in handler
> -> NAPI is scheduled
> -> In NAPI, RX budget is processed and RX interrupts are re-enabled
>
> With the above, on QEMU or fixed link setups (where PHY state doesn't
> matter), there's a chance macb RX interrupt occurs before NAPI is
> enabled. This will result in NAPI being scheduled before it is enabled.
> Fix this macb open by changing the order.
>
> Fixes: ae1f2a56d273 ("net: macb: Added support for many RX queues")
> Signed-off-by: Harini Katakam <[email protected]>

it looks okay to me:
Acked-by: Nicolas Ferre <[email protected]>

> ---
> drivers/net/ethernet/cadence/macb_main.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
> index 5d5c9d7..c049410 100644
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -2427,12 +2427,12 @@ static int macb_open(struct net_device *dev)
> goto pm_exit;
> }
>
> - bp->macbgem_ops.mog_init_rings(bp);
> - macb_init_hw(bp);
> -
> for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue)
> napi_enable(&queue->napi);
>
> + bp->macbgem_ops.mog_init_rings(bp);
> + macb_init_hw(bp);
> +
> /* schedule a link state check */
> phy_start(dev->phydev);
>
>


--
Nicolas Ferre

2019-05-07 19:30:05

by David Miller

Subject: Re: [PATCH] net: macb: Change interrupt and napi enable order in open

From: Harini Katakam <[email protected]>
Date: Tue, 7 May 2019 19:59:10 +0530

> Current order in open:
> -> Enable interrupts (macb_init_hw)
> -> Enable NAPI
> -> Start PHY
>
> Sequence of RX handling:
> -> RX interrupt occurs
> -> Interrupt is cleared and interrupt bits disabled in handler
> -> NAPI is scheduled
> -> In NAPI, RX budget is processed and RX interrupts are re-enabled
>
> With the above, on QEMU or fixed link setups (where PHY state doesn't
> matter), there's a chance macb RX interrupt occurs before NAPI is
> enabled. This will result in NAPI being scheduled before it is enabled.
> Fix this macb open by changing the order.
>
> Fixes: ae1f2a56d273 ("net: macb: Added support for many RX queues")
> Signed-off-by: Harini Katakam <[email protected]>

Applied and queued up for -stable.