[PATCH net-next v2] ppp: remove ppp->closing check

Qingfang Deng
2026-02-02T09:21:23Z

The ppp->closing flag is used to test if an interface is closing down.
However, when .ndo_uninit() is called (where ppp->closing is set to 1),
dev_close() has already brought down the interface, and
synchronize_net() guarantees that no pending TX/RX in the network path
can take place. Thus, the check in the network path is unnecessary.

For file operations - ppp_read(), ppp_write(), and ppp_poll(), can
normally still send or receive skbs. ppp_read() and ppp_poll() are safe
because ppp_dev_uninit() sets pf->dead before waking them up, causing
both to exit cleanly. ppp_write() does not check pf->dead, but
ppp_push() verifies that ppp->channels list is not empty before sending.

Remove the ppp->closing check.

Signed-off-by: Qingfang Deng <dqfext@gmail.com>
---
v2: explain that the race against file operations is safe.
- https://lore.kernel.org/linux-ppp/20241104092434.2677-1-dqfext@gmail.com/

drivers/net/ppp/ppp_generic.c | 38 ++++++++++++-----------------------
1 file changed, 13 insertions(+), 25 deletions(-)

diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index f9f0f16c41d1..c24a2721ac9b 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -142,7 +142,6 @@ struct ppp {
unsigned long last_xmit; /* jiffies when last pkt sent 9c */
unsigned long last_recv; /* jiffies when last pkt rcvd a0 */
struct net_device *dev; /* network interface device a4 */
- int closing; /* is device closing down? a8 */
#ifdef CONFIG_PPP_MULTILINK
int nxchan; /* next channel to send something on */
u32 nxseq; /* next sequence number to send */
@@ -1566,10 +1565,6 @@ static void ppp_dev_uninit(struct net_device *dev)
struct ppp *ppp = netdev_priv(dev);
struct ppp_net *pn = ppp_pernet(ppp->ppp_net);

- ppp_lock(ppp);
- ppp->closing = 1;
- ppp_unlock(ppp);
-
mutex_lock(&pn->all_ppp_mutex);
unit_put(&pn->units_idr, ppp->file.index);
mutex_unlock(&pn->all_ppp_mutex);
@@ -1652,23 +1647,19 @@ static void ppp_setup(struct net_device *dev)
static void __ppp_xmit_process(struct ppp *ppp, struct sk_buff *skb)
{
ppp_xmit_lock(ppp);
- if (!ppp->closing) {
- ppp_push(ppp);
+ ppp_push(ppp);

- if (skb)
- skb_queue_tail(&ppp->file.xq, skb);
- while (!ppp->xmit_pending &&
- (skb = skb_dequeue(&ppp->file.xq)))
- 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))
- netif_wake_queue(ppp->dev);
- else
- netif_stop_queue(ppp->dev);
- } else {
- kfree_skb(skb);
- }
+ if (skb)
+ skb_queue_tail(&ppp->file.xq, skb);
+ while (!ppp->xmit_pending &&
+ (skb = skb_dequeue(&ppp->file.xq)))
+ 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))
+ netif_wake_queue(ppp->dev);
+ else
+ netif_stop_queue(ppp->dev);
ppp_xmit_unlock(ppp);
}

@@ -2218,10 +2209,7 @@ static inline void
ppp_do_recv(struct ppp *ppp, struct sk_buff *skb, struct channel *pch)
{
ppp_recv_lock(ppp);
- if (!ppp->closing)
- ppp_receive_frame(ppp, skb, pch);
- else
- kfree_skb(skb);
+ ppp_receive_frame(ppp, skb, pch);
ppp_recv_unlock(ppp);
}

--
2.43.0