[PATCH 5.5 011/176] Revert "net: dev: introduce support for sch BYPASS for lockless qdisc"

Greg Kroah-Hartman
2020-03-03T17:44:40Z

From: Paolo Abeni <pabeni@redhat.com>

[ Upstream commit 379349e9bc3b42b8b2f8f7a03f64a97623fff323 ]

This reverts commit ba27b4cdaaa66561aaedb2101876e563738d36fe

Ahmed reported ouf-of-order issues bisected to commit ba27b4cdaaa6
("net: dev: introduce support for sch BYPASS for lockless qdisc").
I can't find any working solution other than a plain revert.

This will introduce some minor performance regressions for
pfifo_fast qdisc. I plan to address them in net-next with more
indirect call wrapper boilerplate for qdiscs.

Reported-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Fixes: ba27b4cdaaa6 ("net: dev: introduce support for sch BYPASS for lockless qdisc")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/core/dev.c | 22 ++--------------------
1 file changed, 2 insertions(+), 20 deletions(-)

--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3607,26 +3607,8 @@ static inline int __dev_xmit_skb(struct
qdisc_calculate_pkt_len(skb, q);

if (q->flags & TCQ_F_NOLOCK) {
- if ((q->flags & TCQ_F_CAN_BYPASS) && READ_ONCE(q->empty) &&
- qdisc_run_begin(q)) {
- if (unlikely(test_bit(__QDISC_STATE_DEACTIVATED,
- &q->state))) {
- __qdisc_drop(skb, &to_free);
- rc = NET_XMIT_DROP;
- goto end_run;
- }
- qdisc_bstats_cpu_update(q, skb);
-
- rc = NET_XMIT_SUCCESS;
- if (sch_direct_xmit(skb, q, dev, txq, NULL, true))
- __qdisc_run(q);
-
-end_run:
- qdisc_run_end(q);
- } else {
- rc = q->enqueue(skb, q, &to_free) & NET_XMIT_MASK;
- qdisc_run(q);
- }
+ rc = q->enqueue(skb, q, &to_free) & NET_XMIT_MASK;
+ qdisc_run(q);

if (unlikely(to_free))
kfree_skb_list(to_free);