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Date: Mon, 6 May 2013 17:56:17 +0800
From: Frank Li <lznuaa@...il.com>
To: Lucas Stach <l.stach@...gutronix.de>
Cc: Frank Li <Frank.Li@...escale.com>,
Francois Romieu <romieu@...zoreil.com>,
Robert Schwebel <r.schwebel@...gutronix.de>,
David Miller <davem@...emloft.net>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
Fabio Estevam <festevam@...il.com>,
Shawn Guo <shawn.guo@...aro.org>
Subject: Re: [PATCH v3 1/1 net] net: fec: fix kernel oops when plug/unplug
cable many times
2013/5/6 Lucas Stach <l.stach@...gutronix.de>:
> 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.
Accepted.
>
> fec_restart gets called when duplex or phy speed changes, not only in
> response to a link up/down change.
Yes.
>
>> /* 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.
Accepted.
>
>> +
>> +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.
>
Accepted
>> }
>>
>> 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.
Accepted
>
>> /* 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().
Accepted
>
>> +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.
Bit | & is not atomic.
So I prefer use two variable. the real work in delay work is very
simple for future workaround.
>
>> };
>>
>> 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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