| Message ID | 20240430194401.118950-1-marex@denx.de (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net,v2] net: ks8851: Queue RX packets in IRQ handler instead of disabling BHs | expand |
On Tue, 30 Apr 2024 21:43:34 +0200 Marek Vasut wrote: > diff --git a/drivers/net/ethernet/micrel/ks8851.h b/drivers/net/ethernet/micrel/ks8851.h > index 31f75b4a67fd7..f311074ea13bc 100644 > --- a/drivers/net/ethernet/micrel/ks8851.h > +++ b/drivers/net/ethernet/micrel/ks8851.h > @@ -399,6 +399,7 @@ struct ks8851_net { > > struct work_struct rxctrl_work; > > + struct sk_buff_head rxq; > struct sk_buff_head txq; > unsigned int queued_len; One more round, sorry, this structure has a kdoc, please fill in the description for the new member. > @@ -408,7 +406,8 @@ static irqreturn_t ks8851_irq(int irq, void *_ks) > if (status & IRQ_LCI) > mii_check_link(&ks->mii); > > - local_bh_enable(); > + while (!skb_queue_empty(&ks->rxq)) > + netif_rx(__skb_dequeue(&ks->rxq)); Personal preference and probably not worth retesting but FWIW I'd write this as: while ((skb = __skb_dequeue(&ks->rxq))) netif_rx(skb);
On Wed, May 1, 2024 at 4:10 AM Jakub Kicinski <kuba@kernel.org> wrote: > > On Tue, 30 Apr 2024 21:43:34 +0200 Marek Vasut wrote: > > diff --git a/drivers/net/ethernet/micrel/ks8851.h b/drivers/net/ethernet/micrel/ks8851.h > > index 31f75b4a67fd7..f311074ea13bc 100644 > > --- a/drivers/net/ethernet/micrel/ks8851.h > > +++ b/drivers/net/ethernet/micrel/ks8851.h > > @@ -399,6 +399,7 @@ struct ks8851_net { > > > > struct work_struct rxctrl_work; > > > > + struct sk_buff_head rxq; > > struct sk_buff_head txq; > > unsigned int queued_len; > > One more round, sorry, this structure has a kdoc, please fill in > the description for the new member. Alternative is to use a local (automatic variable on the stack) struct sk_buff_head, no need for permanent storage in struct ks8851_net > > > > @@ -408,7 +406,8 @@ static irqreturn_t ks8851_irq(int irq, void *_ks) > > if (status & IRQ_LCI) > > mii_check_link(&ks->mii); > > > > - local_bh_enable(); > > + while (!skb_queue_empty(&ks->rxq)) > > + netif_rx(__skb_dequeue(&ks->rxq)); > > Personal preference and probably not worth retesting but FWIW I'd write > this as: > > while ((skb = __skb_dequeue(&ks->rxq))) > netif_rx(skb); > -- > pw-bot: cr
On 5/1/24 4:39 AM, Eric Dumazet wrote: > On Wed, May 1, 2024 at 4:10 AM Jakub Kicinski <kuba@kernel.org> wrote: >> >> On Tue, 30 Apr 2024 21:43:34 +0200 Marek Vasut wrote: >>> diff --git a/drivers/net/ethernet/micrel/ks8851.h b/drivers/net/ethernet/micrel/ks8851.h >>> index 31f75b4a67fd7..f311074ea13bc 100644 >>> --- a/drivers/net/ethernet/micrel/ks8851.h >>> +++ b/drivers/net/ethernet/micrel/ks8851.h >>> @@ -399,6 +399,7 @@ struct ks8851_net { >>> >>> struct work_struct rxctrl_work; >>> >>> + struct sk_buff_head rxq; >>> struct sk_buff_head txq; >>> unsigned int queued_len; >> >> One more round, sorry, this structure has a kdoc, please fill in >> the description for the new member. > > Alternative is to use a local (automatic variable on the stack) struct > sk_buff_head, > no need for permanent storage in struct ks8851_net I think that's even better, done in V3 + addressed feedback from Jakub.
diff --git a/drivers/net/ethernet/micrel/ks8851.h b/drivers/net/ethernet/micrel/ks8851.h index 31f75b4a67fd7..f311074ea13bc 100644 --- a/drivers/net/ethernet/micrel/ks8851.h +++ b/drivers/net/ethernet/micrel/ks8851.h @@ -399,6 +399,7 @@ struct ks8851_net { struct work_struct rxctrl_work; + struct sk_buff_head rxq; struct sk_buff_head txq; unsigned int queued_len; diff --git a/drivers/net/ethernet/micrel/ks8851_common.c b/drivers/net/ethernet/micrel/ks8851_common.c index d4cdf3d4f5525..813a41193e3ce 100644 --- a/drivers/net/ethernet/micrel/ks8851_common.c +++ b/drivers/net/ethernet/micrel/ks8851_common.c @@ -299,7 +299,7 @@ static void ks8851_rx_pkts(struct ks8851_net *ks) ks8851_dbg_dumpkkt(ks, rxpkt); skb->protocol = eth_type_trans(skb, ks->netdev); - __netif_rx(skb); + __skb_queue_tail(&ks->rxq, skb); ks->netdev->stats.rx_packets++; ks->netdev->stats.rx_bytes += rxlen; @@ -330,8 +330,6 @@ static irqreturn_t ks8851_irq(int irq, void *_ks) unsigned long flags; unsigned int status; - local_bh_disable(); - ks8851_lock(ks, &flags); status = ks8851_rdreg16(ks, KS_ISR); @@ -408,7 +406,8 @@ static irqreturn_t ks8851_irq(int irq, void *_ks) if (status & IRQ_LCI) mii_check_link(&ks->mii); - local_bh_enable(); + while (!skb_queue_empty(&ks->rxq)) + netif_rx(__skb_dequeue(&ks->rxq)); return IRQ_HANDLED; } @@ -1189,6 +1188,7 @@ int ks8851_probe_common(struct net_device *netdev, struct device *dev, NETIF_MSG_PROBE | NETIF_MSG_LINK); + __skb_queue_head_init(&ks->rxq); skb_queue_head_init(&ks->txq); netdev->ethtool_ops = &ks8851_ethtool_ops;
Currently the driver uses local_bh_disable()/local_bh_enable() in its IRQ handler to avoid triggering net_rx_action() softirq on exit from netif_rx(). The net_rx_action() could trigger this driver .start_xmit callback, which is protected by the same lock as the IRQ handler, so calling the .start_xmit from netif_rx() from the IRQ handler critical section protected by the lock could lead to an attempt to claim the already claimed lock, and a hang. The local_bh_disable()/local_bh_enable() approach works only in case the IRQ handler is protected by a spinlock, but does not work if the IRQ handler is protected by mutex, i.e. this works for KS8851 with Parallel bus interface, but not for KS8851 with SPI bus interface. Remove the BH manipulation and instead of calling netif_rx() inside the IRQ handler code protected by the lock, queue all the received SKBs in the IRQ handler into a queue first, and once the IRQ handler exits the critical section protected by the lock, dequeue all the queued SKBs and push them all into netif_rx(). At this point, it is safe to trigger the net_rx_action() softirq, since the netif_rx() call is outside of the lock that protects the IRQ handler. Fixes: be0384bf599c ("net: ks8851: Handle softirqs at the end of IRQ thread to fix hang") Tested-by: Ronald Wahl <ronald.wahl@raritan.com> # KS8851 SPI Signed-off-by: Marek Vasut <marex@denx.de> --- Cc: "David S. Miller" <davem@davemloft.net> Cc: Eric Dumazet <edumazet@google.com> Cc: Jakub Kicinski <kuba@kernel.org> Cc: Paolo Abeni <pabeni@redhat.com> Cc: Ronald Wahl <ronald.wahl@raritan.com> Cc: Simon Horman <horms@kernel.org> Cc: netdev@vger.kernel.org --- V2: - Add TB from Ronald - Operate private skb queue without locking as suggested by Eric --- Note: This is basically what Jakub originally suggested in https://patchwork.kernel.org/project/netdevbpf/patch/20240331142353.93792-2-marex@denx.de/#25785606 --- drivers/net/ethernet/micrel/ks8851.h | 1 + drivers/net/ethernet/micrel/ks8851_common.c | 8 ++++---- 2 files changed, 5 insertions(+), 4 deletions(-)