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Date: Mon, 06 May 2013 11:19:33 +0200
From: Lucas Stach <l.stach@...gutronix.de>
To: Frank Li <Frank.Li@...escale.com>
Cc: romieu@...zoreil.com, r.schwebel@...gutronix.de,
davem@...emloft.net, netdev@...r.kernel.org, festevam@...il.com,
shawn.guo@...aro.org, lznuaa@...il.com
Subject: Re: [PATCH v3 1/1 net] net: fec: fix kernel oops when plug/unplug
cable many times
Hi Frank,
Am Donnerstag, den 02.05.2013, 08:55 +0800 schrieb Frank Li:
> reproduce steps
> 1. flood ping from other machine
> ping -f -s 41000 IP
> 2. run below script
> while [ 1 ]; do ethtool -s eth0 autoneg off;
> sleep 3;ethtool -s eth0 autoneg on; sleep 4; done;
>
> You can see oops in one hour.
>
> The reason is fec_restart clear BD but NAPI may use it.
> The solution is disable NAPI and stop xmit when reset BD.
> disable NAPI may sleep, so fec_restart can't be call in
> atomic context.
>
> Signed-off-by: Frank Li <Frank.Li@...escale.com>
> ---
> Change from v1 to v2
> * Add netif_tx_lock(ndev) to avoid xmit runing when reset hardware
> Change from v2 to v3
> * Move put real statements after function variable declarations according to David's comments
> * Remove lock in adjust_link according to Lucas Stach's comments
>
> drivers/net/ethernet/freescale/fec.c | 42 +++++++++++++++++++++++++---------
> drivers/net/ethernet/freescale/fec.h | 3 +-
> 2 files changed, 33 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/net/ethernet/freescale/fec.c b/drivers/net/ethernet/freescale/fec.c
> index 73195f6..5a9345c 100644
> --- a/drivers/net/ethernet/freescale/fec.c
> +++ b/drivers/net/ethernet/freescale/fec.c
> @@ -407,6 +407,12 @@ fec_restart(struct net_device *ndev, int duplex)
> u32 rcntl = OPT_FRAME_SIZE | 0x04;
> u32 ecntl = 0x2; /* ETHEREN */
>
> + if (netif_running(ndev)) {
> + napi_disable(&fep->napi);
> + netif_stop_queue(ndev);
> + netif_tx_lock(ndev);
> + }
> +
You did not address the comment from Ben Hutchings here. To make sure we
are not triggering the netdev watchdog immediately when calling
netif_stop_queue() we must call netif_device_detach() when entering the
fec_restart and netif_device_attach() when leaving.
fec_restart gets called when duplex or phy speed changes, not only in
response to a link up/down change.
> /* Whack a reset. We should wait for this. */
> writel(1, fep->hwp + FEC_ECNTRL);
> udelay(10);
> @@ -559,6 +565,12 @@ fec_restart(struct net_device *ndev, int duplex)
>
> /* Enable interrupts we wish to service */
> writel(FEC_DEFAULT_IMASK, fep->hwp + FEC_IMASK);
> +
> + if (netif_running(ndev)) {
> + napi_enable(&fep->napi);
> + netif_wake_queue(ndev);
> + netif_tx_unlock(ndev);
> + }
> }
>
> static void
> @@ -598,8 +610,20 @@ fec_timeout(struct net_device *ndev)
>
> ndev->stats.tx_errors++;
>
> - fec_restart(ndev, fep->full_duplex);
> - netif_wake_queue(ndev);
> + fep->timeout = 1;
> + schedule_delayed_work(&fep->delay_work, msecs_to_jiffies(1));
> +}
Okay, I understand you want to reuse this workqueue to do other things
which might require delayed work so a delay workqueue is fine, but
really use a delay of 0 here.
schedule_delayed_work() internally calls down to queue_delayed_work_on()
where the documentation states: "If delay is zero and dwork is idle, it
will be scheduled for immediate execution.", so this is the right thing
to do here.
> +
> +static void fec_enet_work(struct work_struct *work)
> +{
> + struct fec_enet_private *fep =
> + container_of(work, struct fec_enet_private, delay_work.work);
> +
> + if (fep->timeout) {
> + fep->timeout = 0;
> + fec_restart(fep->netdev, fep->full_duplex);
> + netif_wake_queue(fep->netdev);
> + }
> }
>
> static void
> @@ -970,16 +994,12 @@ static void fec_enet_adjust_link(struct net_device *ndev)
> {
> struct fec_enet_private *fep = netdev_priv(ndev);
> struct phy_device *phy_dev = fep->phy_dev;
> - unsigned long flags;
> -
> int status_change = 0;
>
> - spin_lock_irqsave(&fep->hw_lock, flags);
> -
> /* Prevent a state halted on mii error */
> if (fep->mii_timeout && phy_dev->state == PHY_HALTED) {
> phy_dev->state = PHY_RESUMING;
> - goto spin_unlock;
> + goto exit;
If we bail out here there is zero chance that we detect a link change,
so drop the label and just return here.
> }
>
> if (phy_dev->link) {
> @@ -995,7 +1015,6 @@ static void fec_enet_adjust_link(struct net_device *ndev)
> fep->speed = phy_dev->speed;
> status_change = 1;
> }
> -
Unnecessary whitespace change.
> /* if any of the above changed restart the FEC */
> if (status_change)
> fec_restart(ndev, phy_dev->duplex);
> @@ -1007,11 +1026,10 @@ static void fec_enet_adjust_link(struct net_device *ndev)
> }
> }
>
> -spin_unlock:
> - spin_unlock_irqrestore(&fep->hw_lock, flags);
> -
You are eliminating all users of the hw_lock, so please remove it
altogether. Eliminate it from the fec_enet_private struct and the init
in fec_enet_init().
> +exit:
> if (status_change)
> phy_print_status(phy_dev);
> +
> }
>
> static int fec_enet_mdio_read(struct mii_bus *bus, int mii_id, int regnum)
> @@ -1882,6 +1900,7 @@ fec_probe(struct platform_device *pdev)
> if (ret)
> goto failed_register;
>
> + INIT_DELAYED_WORK(&fep->delay_work, fec_enet_work);
> return 0;
>
> failed_register:
> @@ -1918,6 +1937,7 @@ fec_drv_remove(struct platform_device *pdev)
> struct resource *r;
> int i;
>
> + cancel_delayed_work_sync(&fep->delay_work);
> unregister_netdev(ndev);
> fec_enet_mii_remove(fep);
> del_timer_sync(&fep->time_keep);
> diff --git a/drivers/net/ethernet/freescale/fec.h b/drivers/net/ethernet/freescale/fec.h
> index eb43729..a367b21 100644
> --- a/drivers/net/ethernet/freescale/fec.h
> +++ b/drivers/net/ethernet/freescale/fec.h
> @@ -260,7 +260,8 @@ struct fec_enet_private {
> int hwts_rx_en;
> int hwts_tx_en;
> struct timer_list time_keep;
> -
> + struct delayed_work delay_work;
> + int timeout;
I suspect you are going to add more variables like this in the future if
you are using the workqueue more extensively. This is a massive
pollution of the fec_enet_private struct. Please make this a bitfield
with a proper define for the timeout, so we can reuse one variable for
different tasks, or even split this out into it's own struct for the
delayed tasks.
> };
>
> void fec_ptp_init(struct net_device *ndev, struct platform_device *pdev);
--
Pengutronix e.K. | Lucas Stach |
Industrial Linux Solutions | http://www.pengutronix.de/ |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-5076 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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