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Update ppp TX restart patch to avoid race condition
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com> git-svn-id: svn://svn.openwrt.org/openwrt/trunk@31312 3c298f89-4303-0410-b956-a3cf2f4a3e73
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@ -1,3 +1,32 @@
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commit 9a5d2bd99e0dfe9a31b3c160073ac445ba3d773f
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Author: David Woodhouse <dwmw2@infradead.org>
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Date: Sun Apr 8 10:01:44 2012 +0000
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ppp: Fix race condition with queue start/stop
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Commit e675f0cc9a872fd152edc0c77acfed19bf28b81e ("ppp: Don't stop and
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restart queue on every TX packet") introduced a race condition which
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could leave the net queue stopped even when the channel is no longer
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busy. By calling netif_stop_queue() from ppp_start_xmit(), based on the
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return value from ppp_xmit_process() but *after* all the locks have been
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dropped, we could potentially do so *after* the channel has actually
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finished transmitting and attempted to re-wake the queue.
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Fix this by moving the netif_stop_queue() into ppp_xmit_process() under
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the xmit lock. I hadn't done this previously, because it gets called
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from other places than ppp_start_xmit(). But I now think it's the better
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option. The net queue *should* be stopped if the channel becomes
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congested due to writes from pppd, anyway.
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Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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commit e675f0cc9a872fd152edc0c77acfed19bf28b81e
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Author: David Woodhouse <dwmw2@infradead.org>
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Date: Mon Mar 26 00:03:42 2012 +0000
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ppp: Don't stop and restart queue on every TX packet
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For every transmitted packet, ppp_start_xmit() will stop the netdev
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queue and then, if appropriate, restart it. This causes the TX softirq
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to run, entirely gratuitously.
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@ -21,55 +50,28 @@ place — it's a no-op in the case where the queue wasn't stopped, so it's
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harmless in the TX path.
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Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
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index 159da29..21d7151 100644
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--- a/drivers/net/ppp/ppp_generic.c
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+++ b/drivers/net/ppp/ppp_generic.c
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@@ -235,7 +235,7 @@ struct ppp_net {
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/* Prototypes. */
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static int ppp_unattached_ioctl(struct net *net, struct ppp_file *pf,
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struct file *file, unsigned int cmd, unsigned long arg);
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-static void ppp_xmit_process(struct ppp *ppp);
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+static int ppp_xmit_process(struct ppp *ppp);
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static void ppp_send_frame(struct ppp *ppp, struct sk_buff *skb);
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static void ppp_push(struct ppp *ppp);
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static void ppp_channel_push(struct channel *pch);
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@@ -968,9 +968,9 @@ ppp_start_xmit(struct sk_buff *skb, stru
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@@ -968,7 +968,6 @@ ppp_start_xmit(struct sk_buff *skb, struct net_device *dev)
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proto = npindex_to_proto[npi];
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put_unaligned_be16(proto, pp);
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- netif_stop_queue(dev);
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skb_queue_tail(&ppp->file.xq, skb);
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- ppp_xmit_process(ppp);
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+ if (!ppp_xmit_process(ppp))
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+ netif_stop_queue(dev);
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ppp_xmit_process(ppp);
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return NETDEV_TX_OK;
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outf:
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@@ -1048,10 +1048,11 @@ static void ppp_setup(struct net_device
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* Called to do any work queued up on the transmit side
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* that can now be done.
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*/
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-static void
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+static int
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ppp_xmit_process(struct ppp *ppp)
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{
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struct sk_buff *skb;
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+ int ret = 0;
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ppp_xmit_lock(ppp);
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if (!ppp->closing) {
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@@ -1061,10 +1062,13 @@ ppp_xmit_process(struct ppp *ppp)
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ppp_send_frame(ppp, skb);
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/* If there's no work left to do, tell the core net
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@@ -1063,6 +1062,8 @@ ppp_xmit_process(struct ppp *ppp)
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code that we can accept some more. */
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- if (!ppp->xmit_pending && !skb_peek(&ppp->file.xq))
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+ if (!ppp->xmit_pending && !skb_peek(&ppp->file.xq)) {
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if (!ppp->xmit_pending && !skb_peek(&ppp->file.xq))
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netif_wake_queue(ppp->dev);
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+ ret = 1;
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+ }
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+ else
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+ netif_stop_queue(ppp->dev);
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}
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ppp_xmit_unlock(ppp);
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+ return ret;
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}
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static inline struct sk_buff *
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@ -1,3 +1,32 @@
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commit 9a5d2bd99e0dfe9a31b3c160073ac445ba3d773f
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Author: David Woodhouse <dwmw2@infradead.org>
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Date: Sun Apr 8 10:01:44 2012 +0000
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ppp: Fix race condition with queue start/stop
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Commit e675f0cc9a872fd152edc0c77acfed19bf28b81e ("ppp: Don't stop and
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restart queue on every TX packet") introduced a race condition which
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could leave the net queue stopped even when the channel is no longer
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busy. By calling netif_stop_queue() from ppp_start_xmit(), based on the
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return value from ppp_xmit_process() but *after* all the locks have been
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dropped, we could potentially do so *after* the channel has actually
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finished transmitting and attempted to re-wake the queue.
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Fix this by moving the netif_stop_queue() into ppp_xmit_process() under
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the xmit lock. I hadn't done this previously, because it gets called
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from other places than ppp_start_xmit(). But I now think it's the better
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option. The net queue *should* be stopped if the channel becomes
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congested due to writes from pppd, anyway.
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Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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commit e675f0cc9a872fd152edc0c77acfed19bf28b81e
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Author: David Woodhouse <dwmw2@infradead.org>
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Date: Mon Mar 26 00:03:42 2012 +0000
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ppp: Don't stop and restart queue on every TX packet
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For every transmitted packet, ppp_start_xmit() will stop the netdev
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queue and then, if appropriate, restart it. This causes the TX softirq
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to run, entirely gratuitously.
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@ -21,55 +50,28 @@ place — it's a no-op in the case where the queue wasn't stopped, so it's
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harmless in the TX path.
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Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
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index 159da29..21d7151 100644
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--- a/drivers/net/ppp/ppp_generic.c
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+++ b/drivers/net/ppp/ppp_generic.c
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@@ -235,7 +235,7 @@ struct ppp_net {
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/* Prototypes. */
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static int ppp_unattached_ioctl(struct net *net, struct ppp_file *pf,
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struct file *file, unsigned int cmd, unsigned long arg);
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-static void ppp_xmit_process(struct ppp *ppp);
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+static int ppp_xmit_process(struct ppp *ppp);
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static void ppp_send_frame(struct ppp *ppp, struct sk_buff *skb);
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static void ppp_push(struct ppp *ppp);
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static void ppp_channel_push(struct channel *pch);
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@@ -968,9 +968,9 @@ ppp_start_xmit(struct sk_buff *skb, stru
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@@ -968,7 +968,6 @@ ppp_start_xmit(struct sk_buff *skb, struct net_device *dev)
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proto = npindex_to_proto[npi];
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put_unaligned_be16(proto, pp);
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- netif_stop_queue(dev);
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skb_queue_tail(&ppp->file.xq, skb);
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- ppp_xmit_process(ppp);
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+ if (!ppp_xmit_process(ppp))
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+ netif_stop_queue(dev);
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ppp_xmit_process(ppp);
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return NETDEV_TX_OK;
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outf:
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@@ -1048,10 +1048,11 @@ static void ppp_setup(struct net_device
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* Called to do any work queued up on the transmit side
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* that can now be done.
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*/
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-static void
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+static int
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ppp_xmit_process(struct ppp *ppp)
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{
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struct sk_buff *skb;
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+ int ret = 0;
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ppp_xmit_lock(ppp);
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if (!ppp->closing) {
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@@ -1061,10 +1062,13 @@ ppp_xmit_process(struct ppp *ppp)
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ppp_send_frame(ppp, skb);
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/* If there's no work left to do, tell the core net
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@@ -1063,6 +1062,8 @@ ppp_xmit_process(struct ppp *ppp)
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code that we can accept some more. */
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- if (!ppp->xmit_pending && !skb_peek(&ppp->file.xq))
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+ if (!ppp->xmit_pending && !skb_peek(&ppp->file.xq)) {
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if (!ppp->xmit_pending && !skb_peek(&ppp->file.xq))
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netif_wake_queue(ppp->dev);
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+ ret = 1;
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+ }
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+ else
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+ netif_stop_queue(ppp->dev);
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}
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ppp_xmit_unlock(ppp);
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+ return ret;
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}
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static inline struct sk_buff *
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