summaryrefslogtreecommitdiff
path: root/include/net/sch_generic.h
diff options
context:
space:
mode:
authorJohn Fastabend <john.fastabend@gmail.com>2018-03-24 22:25:06 -0700
committerDavid S. Miller <davem@davemloft.net>2018-03-26 12:36:23 -0400
commiteb82a994479245a79647d302f9b4eb8e7c9d7ca6 (patch)
treef2b46c8bc079ea5f443c9ecbd082e053b39c0f42 /include/net/sch_generic.h
parent743989254ea9f132517806d8893ca9b6cf9dc86b (diff)
net: sched, fix OOO packets with pfifo_fast
After the qdisc lock was dropped in pfifo_fast we allow multiple enqueue threads and dequeue threads to run in parallel. On the enqueue side the skb bit ooo_okay is used to ensure all related skbs are enqueued in-order. On the dequeue side though there is no similar logic. What we observe is with fewer queues than CPUs it is possible to re-order packets when two instances of __qdisc_run() are running in parallel. Each thread will dequeue a skb and then whichever thread calls the ndo op first will be sent on the wire. This doesn't typically happen because qdisc_run() is usually triggered by the same core that did the enqueue. However, drivers will trigger __netif_schedule() when queues are transitioning from stopped to awake using the netif_tx_wake_* APIs. When this happens netif_schedule() calls qdisc_run() on the same CPU that did the netif_tx_wake_* which is usually done in the interrupt completion context. This CPU is selected with the irq affinity which is unrelated to the enqueue operations. To resolve this we add a RUNNING bit to the qdisc to ensure only a single dequeue per qdisc is running. Enqueue and dequeue operations can still run in parallel and also on multi queue NICs we can still have a dequeue in-flight per qdisc, which is typically per CPU. Fixes: c5ad119fb6c0 ("net: sched: pfifo_fast use skb_array") Reported-by: Jakob Unterwurzacher <jakob.unterwurzacher@theobroma-systems.com> Signed-off-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net/sch_generic.h')
-rw-r--r--include/net/sch_generic.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 2092d33194dd..8da32678ce18 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -30,6 +30,7 @@ struct qdisc_rate_table {
enum qdisc_state_t {
__QDISC_STATE_SCHED,
__QDISC_STATE_DEACTIVATED,
+ __QDISC_STATE_RUNNING,
};
struct qdisc_size_table {