77 lines
3.3 KiB
Diff
77 lines
3.3 KiB
Diff
commit 9a5d2bd99e0dfe9a31b3c160073ac445ba3d773f
|
|
Author: David Woodhouse <dwmw2@infradead.org>
|
|
Date: Sun Apr 8 10:01:44 2012 +0000
|
|
|
|
ppp: Fix race condition with queue start/stop
|
|
|
|
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>
|
|
Signed-off-by: David S. Miller <davem@davemloft.net>
|
|
|
|
commit e675f0cc9a872fd152edc0c77acfed19bf28b81e
|
|
Author: David Woodhouse <dwmw2@infradead.org>
|
|
Date: Mon Mar 26 00:03:42 2012 +0000
|
|
|
|
ppp: Don't stop and restart queue on every TX packet
|
|
|
|
For every transmitted packet, ppp_start_xmit() will stop the netdev
|
|
queue and then, if appropriate, restart it. This causes the TX softirq
|
|
to run, entirely gratuitously.
|
|
|
|
This is "only" a waste of CPU time in the normal case, but it's actively
|
|
harmful when the PPP device is a TEQL slave — the wakeup will cause the
|
|
offending device to receive the next TX packet from the TEQL queue, when
|
|
it *should* have gone to the next slave in the list. We end up seeing
|
|
large bursts of packets on just *one* slave device, rather than using
|
|
the full available bandwidth over all slaves.
|
|
|
|
This patch fixes the problem by *not* unconditionally stopping the queue
|
|
in ppp_start_xmit(). It adds a return value from ppp_xmit_process()
|
|
which indicates whether the queue should be stopped or not.
|
|
|
|
It *doesn't* remove the call to netif_wake_queue() from
|
|
ppp_xmit_process(), because other code paths (especially from
|
|
ppp_output_wakeup()) need it there and it's messy to push it out to the
|
|
other callers to do it based on the return value. So we leave it in
|
|
place — it's a no-op in the case where the queue wasn't stopped, so it's
|
|
harmless in the TX path.
|
|
|
|
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
|
|
Signed-off-by: David S. Miller <davem@davemloft.net>
|
|
|
|
|
|
|
|
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
|
|
index 159da29..21d7151 100644
|
|
--- a/drivers/net/ppp/ppp_generic.c
|
|
+++ b/drivers/net/ppp/ppp_generic.c
|
|
@@ -968,7 +968,6 @@ ppp_start_xmit(struct sk_buff *skb, struct net_device *dev)
|
|
proto = npindex_to_proto[npi];
|
|
put_unaligned_be16(proto, pp);
|
|
|
|
- netif_stop_queue(dev);
|
|
skb_queue_tail(&ppp->file.xq, skb);
|
|
ppp_xmit_process(ppp);
|
|
return NETDEV_TX_OK;
|
|
@@ -1063,6 +1062,8 @@ ppp_xmit_process(struct ppp *ppp)
|
|
code that we can accept some more. */
|
|
if (!ppp->xmit_pending && !skb_peek(&ppp->file.xq))
|
|
netif_wake_queue(ppp->dev);
|
|
+ else
|
|
+ netif_stop_queue(ppp->dev);
|
|
}
|
|
ppp_xmit_unlock(ppp);
|
|
}
|