Re: "deadlock" between smc91x driver and link_watch

From: Nicolas Pitre
Date: Fri Nov 26 2004 - 20:43:47 EST


On Thu, 25 Nov 2004, Ian Campbell wrote:

> Hi,
>
> I've taken Nico's comments on board and used lp->work_pending to detect
> whether smc_phy_configure is pending or not instead of dev_hold/put(). I
> was able to do away with smc_phy_configure_wq() from the previous
> version since setting lp->work_pending=0 can safely be done in
> smc_phy_configure() itself, unlike dev_put().
>
> Also fixed a typo 'ence' -> 'Hence' and renamed smc_detect_phy to
> smc_phy_detect in order to follow the same pattern as the other
> smc_phy_* functions, I was typing smc_phy_detect() every time anyway and
> it was getting on my wick. I hope that's OK...
>
> Signed-off-by: Ian Campbell <icampbell@xxxxxxxxx>

Good! Please add "Signed-off-by: Nicolas Pitre <nico@xxxxxxx>" and
send it to Jeff Garzik <jgarzik@xxxxxxxxx>.


> Index: 2.6/drivers/net/smc91x.c
> ===================================================================
> --- 2.6.orig/drivers/net/smc91x.c 2004-11-16 09:26:52.000000000 +0000
> +++ 2.6/drivers/net/smc91x.c 2004-11-25 09:49:38.830953019 +0000
> @@ -203,7 +203,10 @@
> u32 msg_enable;
> u32 phy_type;
> struct mii_if_info mii;
> +
> + /* work queue */
> struct work_struct phy_configure;
> + int work_pending;
>
> spinlock_t lock;
>
> @@ -903,7 +906,7 @@
> /*
> * Finds and reports the PHY address
> */
> -static void smc_detect_phy(struct net_device *dev)
> +static void smc_phy_detect(struct net_device *dev)
> {
> struct smc_local *lp = netdev_priv(dev);
> int phyaddr;
> @@ -1155,6 +1158,7 @@
>
> smc_phy_configure_exit:
> spin_unlock_irq(&lp->lock);
> + lp->work_pending = 0;
> }
>
> /*
> @@ -1350,10 +1354,13 @@
> /*
> * Reconfiguring the PHY doesn't seem like a bad idea here, but
> * smc_phy_configure() calls msleep() which calls schedule_timeout()
> - * which calls schedule(). Ence we use a work queue.
> + * which calls schedule(). Hence we use a work queue.
> */
> - if (lp->phy_type != 0)
> - schedule_work(&lp->phy_configure);
> + if (lp->phy_type != 0) {
> + if (schedule_work(&lp->phy_configure)) {
> + lp->work_pending = 1;
> + }
> + }
>
> /* We can accept TX packets again */
> dev->trans_start = jiffies;
> @@ -1537,7 +1544,18 @@
> smc_shutdown(dev);
>
> if (lp->phy_type != 0) {
> - flush_scheduled_work();
> + /* We need to ensure that no calls to
> + smc_phy_configure are pending.
> +
> + flush_scheduled_work() cannot be called because we
> + are running with the netlink semaphore held (from
> + devinet_ioctl()) and the pending work queue
> + contains linkwatch_event() (scheduled by
> + netif_carrier_off() above). linkwatch_event() also
> + wants the netlink semaphore.
> + */
> + while(lp->work_pending)
> + schedule();
> smc_phy_powerdown(dev, lp->mii.phy_id);
> }
>
> @@ -1904,7 +1922,7 @@
> * Locate the phy, if any.
> */
> if (lp->version >= (CHIP_91100 << 4))
> - smc_detect_phy(dev);
> + smc_phy_detect(dev);
>
> /* Set default parameters */
> lp->msg_enable = NETIF_MSG_LINK;
>
>
> --
> Ian Campbell, Senior Design Engineer
> Web: http://www.arcom.com
> Arcom, Clifton Road, Direct: +44 (0)1223 403 465
> Cambridge CB1 7EA, United Kingdom Phone: +44 (0)1223 411 200
>
>
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>


Nicolas
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