diff options
| author | Jesper Dangaard Brouer <hawk@kernel.org> | 2025-04-25 16:55:31 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-12-07 06:24:54 +0900 |
| commit | bf7528722e936a625673252f62eac5ed027d53ec (patch) | |
| tree | 3860636613552e4c485e384158f4718e9e74b9da /include/net | |
| parent | 429bcd8ffa53103fdd1541f326529ac082cd04ae (diff) | |
net: sched: generalize check for no-queue qdisc on TX queue
[ Upstream commit 34dd0fecaa02d654c447d43a7e4c72f9b18b7033 ]
The "noqueue" qdisc can either be directly attached, or get default
attached if net_device priv_flags has IFF_NO_QUEUE. In both cases, the
allocated Qdisc structure gets it's enqueue function pointer reset to
NULL by noqueue_init() via noqueue_qdisc_ops.
This is a common case for software virtual net_devices. For these devices
with no-queue, the transmission path in __dev_queue_xmit() will bypass
the qdisc layer. Directly invoking device drivers ndo_start_xmit (via
dev_hard_start_xmit). In this mode the device driver is not allowed to
ask for packets to be queued (either via returning NETDEV_TX_BUSY or
stopping the TXQ).
The simplest and most reliable way to identify this no-queue case is by
checking if enqueue == NULL.
The vrf driver currently open-codes this check (!qdisc->enqueue). While
functionally correct, this low-level detail is better encapsulated in a
dedicated helper for clarity and long-term maintainability.
To make this behavior more explicit and reusable, this patch introduce a
new helper: qdisc_txq_has_no_queue(). Helper will also be used by the
veth driver in the next patch, which introduces optional qdisc-based
backpressure.
This is a non-functional change.
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Jesper Dangaard Brouer <hawk@kernel.org>
Link: https://patch.msgid.link/174559293172.827981.7583862632045264175.stgit@firesoul
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: a14602fcae17 ("veth: reduce XDP no_direct return section to fix race")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'include/net')
| -rw-r--r-- | include/net/sch_generic.h | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index a9d7e9ecee6b..1e002b1dea62 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -803,6 +803,14 @@ static inline bool qdisc_tx_changing(const struct net_device *dev) return false; } +/* "noqueue" qdisc identified by not having any enqueue, see noqueue_init() */ +static inline bool qdisc_txq_has_no_queue(const struct netdev_queue *txq) +{ + struct Qdisc *qdisc = rcu_access_pointer(txq->qdisc); + + return qdisc->enqueue == NULL; +} + /* Is the device using the noop qdisc on all queues? */ static inline bool qdisc_tx_is_noop(const struct net_device *dev) { |