| Message ID | 1333915304.31812.63.camel@shinybook.infradead.org |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: David Woodhouse <dwmw2@infradead.org> Date: Sun, 08 Apr 2012 21:01:44 +0100 > Commit e675f0cc9a872fd152edc0c77acfed19bf28b81e ("ppp: Don't stop and > restart queue on every TX packet") introduced a race condition which > could leave the net queue stopped even when the channel is no longer > busy. By calling netif_stop_queue() from ppp_start_xmit(), based on the > return value from ppp_xmit_process() but *after* all the locks have been > dropped, we could potentially do so *after* the channel has actually > finished transmitting and attempted to re-wake the queue. > > Fix this by moving the netif_stop_queue() into ppp_xmit_process() under > the xmit lock. I hadn't done this previously, because it gets called > from other places than ppp_start_xmit(). But I now think it's the better > option. The net queue *should* be stopped if the channel becomes > congested due to writes from pppd, anyway. > > Signed-off-by: David Woodhouse <David.Woodhouse@intel.com> Applied, thanks David. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c index 33f8c51..21d7151 100644 --- a/drivers/net/ppp/ppp_generic.c +++ b/drivers/net/ppp/ppp_generic.c @@ -235,7 +235,7 @@ struct ppp_net { /* Prototypes. */ static int ppp_unattached_ioctl(struct net *net, struct ppp_file *pf, struct file *file, unsigned int cmd, unsigned long arg); -static int ppp_xmit_process(struct ppp *ppp); +static void ppp_xmit_process(struct ppp *ppp); static void ppp_send_frame(struct ppp *ppp, struct sk_buff *skb); static void ppp_push(struct ppp *ppp); static void ppp_channel_push(struct channel *pch); @@ -969,8 +969,7 @@ ppp_start_xmit(struct sk_buff *skb, struct net_device *dev) put_unaligned_be16(proto, pp); skb_queue_tail(&ppp->file.xq, skb); - if (!ppp_xmit_process(ppp)) - netif_stop_queue(dev); + ppp_xmit_process(ppp); return NETDEV_TX_OK; outf: @@ -1048,11 +1047,10 @@ static void ppp_setup(struct net_device *dev) * Called to do any work queued up on the transmit side * that can now be done. */ -static int +static void ppp_xmit_process(struct ppp *ppp) { struct sk_buff *skb; - int ret = 0; ppp_xmit_lock(ppp); if (!ppp->closing) { @@ -1062,13 +1060,12 @@ ppp_xmit_process(struct ppp *ppp) ppp_send_frame(ppp, skb); /* If there's no work left to do, tell the core net code that we can accept some more. */ - if (!ppp->xmit_pending && !skb_peek(&ppp->file.xq)) { + if (!ppp->xmit_pending && !skb_peek(&ppp->file.xq)) netif_wake_queue(ppp->dev); - ret = 1; - } + else + netif_stop_queue(ppp->dev); } ppp_xmit_unlock(ppp); - return ret; } static inline struct sk_buff *
Commit e675f0cc9a872fd152edc0c77acfed19bf28b81e ("ppp: Don't stop and restart queue on every TX packet") introduced a race condition which could leave the net queue stopped even when the channel is no longer busy. By calling netif_stop_queue() from ppp_start_xmit(), based on the return value from ppp_xmit_process() but *after* all the locks have been dropped, we could potentially do so *after* the channel has actually finished transmitting and attempted to re-wake the queue. Fix this by moving the netif_stop_queue() into ppp_xmit_process() under the xmit lock. I hadn't done this previously, because it gets called from other places than ppp_start_xmit(). But I now think it's the better option. The net queue *should* be stopped if the channel becomes congested due to writes from pppd, anyway. Signed-off-by: David Woodhouse <David.Woodhouse@intel.com> --- drivers/net/ppp/ppp_generic.c | 15 ++++++--------- 1 files changed, 6 insertions(+), 9 deletions(-)