Re: [Xen-devel] [PATCH] add netconsole support for xen-netfront

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2012-01-12 at 14:17 +0000, Konrad Rzeszutek Wilk wrote:
> On Wed, Jan 11, 2012 at 04:52:36PM +0800, Zhenzhong Duan wrote:
> > add polling interface to xen-netfront device to support netconsole
> > 
> 
> Ian, any thoughts on the spinlock changes?

What are they for?

At a guess they are a necessary consequence of the new calling context.
However not all the drivers I looked at which supported netpool were
using the irqsave variants in this context so I guess it must be some
secondary effect.

Anyway, the upshot is that I think the changelog needs to explain the
rationale for the locking change.

Ian.

> 
> > Signed-off-by: Tina.Yang <tina.yang@xxxxxxxxxx>
> > Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
> > Signed-off-by: Zhenzhong.Duan <zhenzhong.duan@xxxxxxxxxx>
> > Tested-by: gurudas.pai <gurudas.pai@xxxxxxxxxx>
> > ---
> >  drivers/net/xen-netfront.c |   57 
> > ++++++++++++++++++++++++++-----------------
> >  1 files changed, 34 insertions(+), 23 deletions(-)
> > 
> > diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
> > index fa67905..db638b4 100644
> > --- a/drivers/net/xen-netfront.c
> > +++ b/drivers/net/xen-netfront.c
> > @@ -489,6 +489,7 @@ static int xennet_start_xmit(struct sk_buff *skb, 
> > struct net_device *dev)
> >     int frags = skb_shinfo(skb)->nr_frags;
> >     unsigned int offset = offset_in_page(data);
> >     unsigned int len = skb_headlen(skb);
> > +   unsigned long flags;
> >  
> >     frags += DIV_ROUND_UP(offset + len, PAGE_SIZE);
> >     if (unlikely(frags > MAX_SKB_FRAGS + 1)) {
> > @@ -498,12 +499,12 @@ static int xennet_start_xmit(struct sk_buff *skb, 
> > struct net_device *dev)
> >             goto drop;
> >     }
> >  
> > -   spin_lock_irq(&np->tx_lock);
> > +   spin_lock_irqsave(&np->tx_lock, flags);
> >  
> >     if (unlikely(!netif_carrier_ok(dev) ||
> >                  (frags > 1 && !xennet_can_sg(dev)) ||
> >                  netif_needs_gso(skb, netif_skb_features(skb)))) {
> > -           spin_unlock_irq(&np->tx_lock);
> > +           spin_unlock_irqrestore(&np->tx_lock, flags);
> >             goto drop;
> >     }
> >  
> > @@ -574,7 +575,7 @@ static int xennet_start_xmit(struct sk_buff *skb, 
> > struct net_device *dev)
> >     if (!netfront_tx_slot_available(np))
> >             netif_stop_queue(dev);
> >  
> > -   spin_unlock_irq(&np->tx_lock);
> > +   spin_unlock_irqrestore(&np->tx_lock, flags);
> >  
> >     return NETDEV_TX_OK;
> >  
> > @@ -1228,6 +1229,33 @@ static int xennet_set_features(struct net_device 
> > *dev,
> >     return 0;
> >  }
> >  
> > +static irqreturn_t xennet_interrupt(int irq, void *dev_id)
> > +{
> > +   struct net_device *dev = dev_id;
> > +   struct netfront_info *np = netdev_priv(dev);
> > +   unsigned long flags;
> > +
> > +   spin_lock_irqsave(&np->tx_lock, flags);
> > +
> > +   if (likely(netif_carrier_ok(dev))) {
> > +           xennet_tx_buf_gc(dev);
> > +           /* Under tx_lock: protects access to rx shared-ring indexes. */
> > +           if (RING_HAS_UNCONSUMED_RESPONSES(&np->rx))
> > +                   napi_schedule(&np->napi);
> > +   }
> > +
> > +   spin_unlock_irqrestore(&np->tx_lock, flags);
> > +
> > +   return IRQ_HANDLED;
> > +}
> > +
> > +#ifdef CONFIG_NET_POLL_CONTROLLER
> > +static void xennet_poll_controller(struct net_device *dev)
> > +{
> > +   xennet_interrupt(0, dev);
> > +}
> > +#endif
> > +
> >  static const struct net_device_ops xennet_netdev_ops = {
> >     .ndo_open            = xennet_open,
> >     .ndo_uninit          = xennet_uninit,
> > @@ -1239,6 +1267,9 @@ static const struct net_device_ops xennet_netdev_ops 
> > = {
> >     .ndo_validate_addr   = eth_validate_addr,
> >     .ndo_fix_features    = xennet_fix_features,
> >     .ndo_set_features    = xennet_set_features,
> > +#ifdef CONFIG_NET_POLL_CONTROLLER
> > +   .ndo_poll_controller = xennet_poll_controller,
> > +#endif
> >  };
> >  
> >  static struct net_device * __devinit xennet_create_dev(struct 
> > xenbus_device *dev)
> > @@ -1448,26 +1479,6 @@ static int xen_net_read_mac(struct xenbus_device 
> > *dev, u8 mac[])
> >     return 0;
> >  }
> >  
> > -static irqreturn_t xennet_interrupt(int irq, void *dev_id)
> > -{
> > -   struct net_device *dev = dev_id;
> > -   struct netfront_info *np = netdev_priv(dev);
> > -   unsigned long flags;
> > -
> > -   spin_lock_irqsave(&np->tx_lock, flags);
> > -
> > -   if (likely(netif_carrier_ok(dev))) {
> > -           xennet_tx_buf_gc(dev);
> > -           /* Under tx_lock: protects access to rx shared-ring indexes. */
> > -           if (RING_HAS_UNCONSUMED_RESPONSES(&np->rx))
> > -                   napi_schedule(&np->napi);
> > -   }
> > -
> > -   spin_unlock_irqrestore(&np->tx_lock, flags);
> > -
> > -   return IRQ_HANDLED;
> > -}
> > -
> >  static int setup_netfront(struct xenbus_device *dev, struct netfront_info 
> > *info)
> >  {
> >     struct xen_netif_tx_sring *txs;
> > -- 
> > 1.7.3



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