[PATCH net v5 0/6] can: fix bus-off restart and device close races

[PATCH net v5 0/6] can: fix bus-off restart and device close races

[Cunhao Lu via B4 Relay]

This work started from a real failure on a production robot using a
LubanCat-5IO with an RK3588. RX continued, but the TX queue remained
stopped and subsequent sends returned ENOBUFS. The interface still
reported ERROR-ACTIVE, and the hardware indicated neither a bus-off
condition nor a pending TX request.

While testing the echo-loss fix with fault injection, I discovered a
separate race between bus-off restart and device close. This series fixes
that race; the fix for the original TX stall will follow separately.

Rockchip currently cancels restart_work in close_candev(), after freeing
the IRQ, disabling RX offload and stopping the controller. A concurrent
restart can re-enable the controller and interrupts after IRQ teardown,
and requeue timestamp work that accesses registers after runtime suspend
has disabled the controller clocks.

The CAN core checks netif_running() before scheduling or starting
recovery. A new close_candev_cancel_restart_sync() helper lets Rockchip
wait for any restart already in progress before tearing down resources.
The final close_candev() call retains cancellation and echo cleanup.

Rockchip restart masks the device's interrupts and drains active IRQ
handlers without disabling the shared interrupt line. It also drains
timestamp work before reinitializing the controller and timecounter.
Shared IRQ handling stays suspended until initialization is complete.
Timestamp locking prevents workers from rearming after deactivation and
keeps timestamp conversions consistent with timecounter updates.

The bus-off path drains TX submission and RX-side echo users before
publishing BUS_OFF, protecting the CAN core's echo flush during manual
recovery. Consumed RX FIFO entries are dropped while TX is disabled to
prevent self-transmitted frames from reaching ordinary RX. Startup
serializes carrier restoration, IRQ resumption and queue wake with a new
bus-off. The series also fixes RX offload cleanup when request_irq() fails
during open.

The following issues were also identified during this work:

- Races in the Rockchip bus error counter cache.
- Incomplete runtime PM clock cleanup in Rockchip during removal or
  failed registration.

These two issues are outside this series. When I have time,
I will send separate patches to fix them one by one.

Hardware testing used a LubanCat-5IO running a Linux 6.18 PREEMPT_RT
kernel with this series backported. Tests covered 2,700 ranging
request/response exchanges and 630 seconds of continuous traffic,
including three naturally scheduled timestamp worker runs. RX, TX echo
and TX completion hardware timestamps were present throughout, with no
backward or abnormal jumps.

Test-only instrumentation captured 20 close/IRQ interleavings, including
15 with multiple FIFO entries. In every case, consumed self-transmitted
frames were dropped after TX was disabled, the FIFO was drained, and
traffic resumed after reopening.

All 100 classic CAN loopback tests, 20 automatic and 20 manual restarts
using synthetic bus-off injection, and 20 down/up cycles passed. No
timestamp worker ran during about 300 seconds after close, and no
deadlocks or WARN/Oops were observed.

---
Changes in v5:
- Drop consumed RX FIFO entries under tx_lock when TX is disabled
  instead of only skipping echo filtering.
- Link to v4:
  https://patch.msgid.link/20261015-rockchip-canfd-restart-close-v4-0-ad149ff79450@qq.com

Changes in v4:
- Serialize timecounter_cyc2time() with the worker's timecounter_read()
  and startup's timecounter_init() using timestamp_lock.
- Update rkcanfd_skb_set_timestamp() to take a non-const private pointer
  and document the expanded scope of timestamp_lock.
- Link to v3:
  https://patch.msgid.link/20261014-rockchip-canfd-restart-close-v3-0-f0eb41090242@qq.com

Changes in v3:
- Replace disable_irq()/enable_irq() in Rockchip restart with device
  interrupt masking, mask readback, irq_suspended and synchronize_irq().
- Use release/acquire ordering when resuming the IRQ handler.
- Initialize timestamp delayed work once at probe and synchronously
  cancel it before restart reinitializes the timecounter.
- Balance RX offload enablement when request_irq() fails during open.
- Prevent timestamp work from reading the counter or rearming after
  deactivation, with cancellation outside the lock.
- Drain TX submission and RX-side echo users before publishing BUS_OFF,
  protecting the core's pre-restart echo flush.
- Serialize carrier restoration, IRQ enablement and queue wake with a new
  bus-off; suspend shared IRQ handling during open until startup finishes.
- Link to v2:
  https://lore.kernel.org/linux-can/tencent_82C93561D200C84C24608C80049C23EEF80A@qq.com/

Changes in v2:
- Split the series into the common checks, the cancellation helper, and
  its use in Rockchip.
- Check netif_running() after the do_set_mode capability check and before
  the restart notification, echo cleanup, and carrier update.
- Only queue automatic recovery for a running interface; keep reporting
  bus-off and make the log message match the scheduling decision.
- Add close_candev_cancel_restart_sync() in linux/can/dev.h and use it in
  close_candev() without changing the existing cleanup order.
- Replace the Rockchip mutex and closing flag with an early call to the
  helper. Drop the extra close-path IRQ synchronization and mask readback.
- Retain IRQ exclusion around hardware reinitialization in the restart
  callback.
- Link to v1:
  https://lore.kernel.org/linux-can/tencent_5802EE88434010229EDF7A53084D994C6106@qq.com/

To: Marc Kleine-Budde <mkl@pengutronix.de>
To: Vincent Mailhol <mailhol@kernel.org>
To: Heiko Stuebner <heiko@sntech.de>
To: "David S. Miller" <davem@davemloft.net>
To: Wolfgang Grandegger <wg@grandegger.com>
To: Oliver Hartkopp <socketcan@hartkopp.net>
To: kernel@pengutronix.de
Cc: linux-can@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-rockchip@lists.infradead.org

---
Cunhao Lu (6):
      can: dev: prevent bus-off recovery when the interface is not running
      can: dev: add close_candev_cancel_restart_sync()
      can: rockchip_canfd: cancel bus-off restart before closing the device
      can: rockchip_canfd: prevent timestamp work from rearming after bus-off
      can: rockchip_canfd: serialize TX with bus-off and restart
      can: rockchip_canfd: serialize timecounter timestamp conversion

 drivers/net/can/dev/dev.c                          | 12 ++--
 drivers/net/can/rockchip/rockchip_canfd-core.c     | 67 ++++++++++++++++++++--
 drivers/net/can/rockchip/rockchip_canfd-rx.c       | 26 ++++++---
 .../net/can/rockchip/rockchip_canfd-timestamp.c    | 43 ++++++++++++--
 drivers/net/can/rockchip/rockchip_canfd-tx.c       | 16 +++++-
 drivers/net/can/rockchip/rockchip_canfd.h          | 11 +++-
 include/linux/can/dev.h                            | 12 ++++
 7 files changed, 162 insertions(+), 25 deletions(-)
---
base-commit: 24a19b953e2a3d0ea5a8c4951a0ab8f32720c907
change-id: 20261013-rockchip-canfd-restart-close-ebde5954f1bf

Best regards,
--  
Cunhao Lu <1579567540@qq.com>

[PATCH net v5 1/6] can: dev: prevent bus-off recovery when the interface is not running

[Cunhao Lu via B4 Relay]

From: Cunhao Lu <1579567540@qq.com>

The networking core clears __LINK_STATE_START before calling ndo_stop(),
but CAN bus-off recovery neither checks this state before queuing work
nor before calling the driver's restart callback. Recovery can therefore
be queued or started after the interface has begun closing, potentially
re-enabling hardware while the driver is tearing it down.

Check netif_running() in can_restart() before flushing echo skbs, sending
the restart notification or enabling the carrier. Keep the existing
unsupported-operation check first. In can_bus_off(), only schedule
recovery for a running interface and make the log message reflect that
decision. Keep reporting bus-off and disabling the carrier.

These checks do not wait for recovery that has already passed the check,
nor serialize the check with work submission. Drivers still need to
cancel restart work before tearing down resources and quiesce its
producers before their final cleanup.

Fixes: 39549eef3587 ("can: CAN Network device driver and Netlink interface")
Cc: stable@vger.kernel.org
Signed-off-by: Cunhao Lu <1579567540@qq.com>
---
 drivers/net/can/dev/dev.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/can/dev/dev.c b/drivers/net/can/dev/dev.c
index 769745e22a3c7..92492c503446e 100644
--- a/drivers/net/can/dev/dev.c
+++ b/drivers/net/can/dev/dev.c
@@ -198,6 +198,9 @@ static int can_restart(struct net_device *dev)
 	if (!priv->do_set_mode)
 		return -EOPNOTSUPP;
 
+	if (!netif_running(dev))
+		return -ENETDOWN;
+
 	if (netif_carrier_ok(dev))
 		netdev_err(dev, "Attempt to restart for bus-off recovery, but carrier is OK?\n");
 
@@ -264,8 +267,9 @@ int can_restart_now(struct net_device *dev)
 void can_bus_off(struct net_device *dev)
 {
 	struct can_priv *priv = netdev_priv(dev);
+	const bool restart = priv->restart_ms && netif_running(dev);
 
-	if (priv->restart_ms)
+	if (restart)
 		netdev_info(dev, "bus-off, scheduling restart in %d ms\n",
 			    priv->restart_ms);
 	else
@@ -273,7 +277,7 @@ void can_bus_off(struct net_device *dev)
 
 	netif_carrier_off(dev);
 
-	if (priv->restart_ms)
+	if (restart)
 		schedule_delayed_work(&priv->restart_work,
 				      msecs_to_jiffies(priv->restart_ms));
 }

-- 
2.34.1

[PATCH net v5 2/6] can: dev: add close_candev_cancel_restart_sync()

[Cunhao Lu via B4 Relay]

From: Cunhao Lu <1579567540@qq.com>

Drivers may need to wait for bus-off recovery before tearing down the
IRQ and hardware resources used by their restart callback. Calling
close_candev() at that point also flushes echo skbs, which belongs after
the driver has quiesced the users of those buffers.

Add close_candev_cancel_restart_sync() in linux/can/dev.h so drivers can
cancel the core restart work separately, without accessing can_priv's
work item directly. The helper only cancels restart work; callers must
still stop its producers and call close_candev() for the final cleanup.

Use the helper in close_candev(), preserving its existing cancellation
and echo cleanup order.

Cc: stable@vger.kernel.org
Signed-off-by: Cunhao Lu <1579567540@qq.com>
---
 drivers/net/can/dev/dev.c |  4 +---
 include/linux/can/dev.h   | 12 ++++++++++++
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/net/can/dev/dev.c b/drivers/net/can/dev/dev.c
index 92492c503446e..52e8c4854ae0d 100644
--- a/drivers/net/can/dev/dev.c
+++ b/drivers/net/can/dev/dev.c
@@ -534,9 +534,7 @@ EXPORT_SYMBOL_GPL(of_can_transceiver);
  */
 void close_candev(struct net_device *dev)
 {
-	struct can_priv *priv = netdev_priv(dev);
-
-	cancel_delayed_work_sync(&priv->restart_work);
+	close_candev_cancel_restart_sync(dev);
 	can_flush_echo_skb(dev);
 }
 EXPORT_SYMBOL_GPL(close_candev);
diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
index 6d0710d6f571d..a277d12332f15 100644
--- a/include/linux/can/dev.h
+++ b/include/linux/can/dev.h
@@ -22,6 +22,7 @@
 #include <linux/can/skb.h>
 #include <linux/ethtool.h>
 #include <linux/netdevice.h>
+#include <linux/workqueue.h>
 
 /*
  * CAN mode
@@ -115,6 +116,17 @@ struct can_priv *safe_candev_priv(struct net_device *dev);
 
 int open_candev(struct net_device *dev);
 void close_candev(struct net_device *dev);
+
+/* Cancel bus-off restart before tearing down resources used by the restart
+ * callback. The driver must still call close_candev() for the final cleanup.
+ */
+static inline void close_candev_cancel_restart_sync(struct net_device *dev)
+{
+	struct can_priv *priv = netdev_priv(dev);
+
+	cancel_delayed_work_sync(&priv->restart_work);
+}
+
 void can_set_default_mtu(struct net_device *dev);
 void can_set_cap_info(struct net_device *dev);
 int __must_check can_set_static_ctrlmode(struct net_device *dev,

-- 
2.34.1

[PATCH net v5 3/6] can: rockchip_canfd: cancel bus-off restart before closing the device

[Cunhao Lu via B4 Relay]

From: Cunhao Lu <1579567540@qq.com>

The close path cancels restart_work in close_candev() only after freeing
the IRQ, disabling RX offload and stopping the controller. A concurrent
restart can re-enable the controller and interrupts after IRQ teardown,
or requeue timestamp work that accesses registers after runtime suspend
has disabled the controller clocks.

Call close_candev_cancel_restart_sync() at the start of ndo_stop(), while
the resources needed by a running restart are still available. Keep
close_candev() after IRQ teardown for final cancellation and echo cleanup.

During restart, mask the device's interrupts and drain active handlers
without disabling the shared IRQ line. Suspend handler access to the
controller until reinitialization is complete, and publish the initialized
state before resuming IRQ handling.

Drain timestamp work before reinitializing the timecounter, and initialize
the delayed work once at probe. Keep asynchronous cancellation in the
bus-off path. Also disable RX offload if request_irq() fails during open.

Fixes: ff60bfbaf67f ("can: rockchip_canfd: add driver for Rockchip CAN-FD controller")
Cc: stable@vger.kernel.org
Signed-off-by: Cunhao Lu <1579567540@qq.com>

---
Changes in v3:
- Replace disable_irq()/enable_irq() with device interrupt masking,
  mask readback, an irq_suspended flag and synchronize_irq().
- Pair release/acquire accesses to publish reinitialized state before
  the IRQ handler resumes, without disabling other shared IRQ users.
- Initialize timestamp delayed work once at probe and synchronously
  cancel it before reinitializing the timestamp state during restart.
- Disable RX offload when request_irq() fails during open.
---
 drivers/net/can/rockchip/rockchip_canfd-core.c      | 20 ++++++++++++++++++++
 drivers/net/can/rockchip/rockchip_canfd-timestamp.c |  6 +++++-
 drivers/net/can/rockchip/rockchip_canfd.h           |  2 ++
 3 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/net/can/rockchip/rockchip_canfd-core.c b/drivers/net/can/rockchip/rockchip_canfd-core.c
index 37c1c22c40c9f..4b3db07242395 100644
--- a/drivers/net/can/rockchip/rockchip_canfd-core.c
+++ b/drivers/net/can/rockchip/rockchip_canfd-core.c
@@ -20,6 +20,7 @@
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
+#include <linux/smp.h>
 #include <linux/string.h>
 
 #include "rockchip_canfd.h"
@@ -356,7 +357,18 @@ static int rkcanfd_set_mode(struct net_device *ndev,
 
 	switch (mode) {
 	case CAN_MODE_START:
+		rkcanfd_chip_interrupts_disable(priv);
+		/* Flush the interrupt mask write before suspending the handler. */
+		rkcanfd_read(priv, RKCANFD_REG_INT_MASK);
+		/* Keep shared IRQs from accessing the device during restart. */
+		WRITE_ONCE(priv->irq_suspended, true);
+		/* Wait for handlers that already passed the suspended check. */
+		synchronize_irq(ndev->irq);
+		rkcanfd_timestamp_stop_sync(priv);
+
 		rkcanfd_chip_start(priv);
+		/* Publish the initialized state before resuming IRQ handling. */
+		smp_store_release(&priv->irq_suspended, false);
 		rkcanfd_chip_interrupts_enable(priv);
 		netif_wake_queue(ndev);
 		break;
@@ -666,6 +678,10 @@ static irqreturn_t rkcanfd_irq(int irq, void *dev_id)
 	struct rkcanfd_priv *priv = dev_id;
 	u32 reg_int_unmasked, reg_int;
 
+	/* Pairs with the release after restart has initialized the device. */
+	if (smp_load_acquire(&priv->irq_suspended))
+		return IRQ_NONE;
+
 	reg_int_unmasked = rkcanfd_read(priv, RKCANFD_REG_INT);
 	reg_int = reg_int_unmasked & ~priv->reg_int_mask_default;
 
@@ -747,6 +763,7 @@ static int rkcanfd_open(struct net_device *ndev)
 	return 0;
 
 out_rkcanfd_chip_stop:
+	can_rx_offload_disable(&priv->offload);
 	rkcanfd_chip_stop_sync(priv, CAN_STATE_STOPPED);
 	pm_runtime_put(ndev->dev.parent);
 out_close_candev:
@@ -758,6 +775,7 @@ static int rkcanfd_stop(struct net_device *ndev)
 {
 	struct rkcanfd_priv *priv = netdev_priv(ndev);
 
+	close_candev_cancel_restart_sync(ndev);
 	netif_stop_queue(ndev);
 
 	rkcanfd_chip_interrupts_disable(priv);
@@ -934,6 +952,8 @@ static int rkcanfd_probe(struct platform_device *pdev)
 	if (err)
 		goto out_free_candev;
 
+	rkcanfd_timestamp_work_init(priv);
+
 	err = rkcanfd_register(priv);
 	if (err)
 		goto out_can_rx_offload_del;
diff --git a/drivers/net/can/rockchip/rockchip_canfd-timestamp.c b/drivers/net/can/rockchip/rockchip_canfd-timestamp.c
index 72774cd2f94b7..ad582afbbd682 100644
--- a/drivers/net/can/rockchip/rockchip_canfd-timestamp.c
+++ b/drivers/net/can/rockchip/rockchip_canfd-timestamp.c
@@ -37,6 +37,11 @@ static void rkcanfd_timestamp_work(struct work_struct *work)
 	schedule_delayed_work(&priv->timestamp, priv->work_delay_jiffies);
 }
 
+void rkcanfd_timestamp_work_init(struct rkcanfd_priv *priv)
+{
+	INIT_DELAYED_WORK(&priv->timestamp, rkcanfd_timestamp_work);
+}
+
 void rkcanfd_timestamp_init(struct rkcanfd_priv *priv)
 {
 	const struct can_bittiming *dbt = &priv->can.fd.data_bittiming;
@@ -73,7 +78,6 @@ void rkcanfd_timestamp_init(struct rkcanfd_priv *priv)
 	max_cycles = min(max_cycles, cc->mask);
 	work_delay_ns = clocksource_cyc2ns(max_cycles, cc->mult, cc->shift);
 	priv->work_delay_jiffies = div_u64(work_delay_ns, 3u * NSEC_PER_SEC / HZ);
-	INIT_DELAYED_WORK(&priv->timestamp, rkcanfd_timestamp_work);
 
 	netdev_dbg(priv->ndev, "clock=%lu.%02luMHz bitrate=%lu.%02luMBit/s div=%u rate=%lu.%02luMHz mult=%u shift=%u delay=%lus\n",
 		   priv->can.clock.freq / MEGA,
diff --git a/drivers/net/can/rockchip/rockchip_canfd.h b/drivers/net/can/rockchip/rockchip_canfd.h
index 95bea9bfd8a2f..e1debab54534e 100644
--- a/drivers/net/can/rockchip/rockchip_canfd.h
+++ b/drivers/net/can/rockchip/rockchip_canfd.h
@@ -480,6 +480,7 @@ struct rkcanfd_priv {
 
 	u32 reg_mode_default;
 	u32 reg_int_mask_default;
+	bool irq_suspended;
 	struct rkcanfd_devtype_data devtype_data;
 
 	struct cyclecounter cc;
@@ -551,6 +552,7 @@ int rkcanfd_handle_rx_int(struct rkcanfd_priv *priv);
 
 void rkcanfd_skb_set_timestamp(const struct rkcanfd_priv *priv,
 			       struct sk_buff *skb, const u32 timestamp);
+void rkcanfd_timestamp_work_init(struct rkcanfd_priv *priv);
 void rkcanfd_timestamp_init(struct rkcanfd_priv *priv);
 void rkcanfd_timestamp_start(struct rkcanfd_priv *priv);
 void rkcanfd_timestamp_stop(struct rkcanfd_priv *priv);

-- 
2.34.1

[PATCH net v5 4/6] can: rockchip_canfd: prevent timestamp work from rearming after bus-off

[Cunhao Lu via B4 Relay]

From: Cunhao Lu <1579567540@qq.com>

The bus-off IRQ cancels timestamp work asynchronously. If the worker
is already running, it can requeue itself after cancellation and keep
polling while the controller remains bus-off.

Add a dedicated lock and an active flag, initialized once at probe.
Serialize the worker's active check, counter read and self-requeue with
start and stop. Clear the flag under the lock before cancelling work
so no worker can read the counter or rearm after deactivation. Enable
the flag and schedule the initial work under the same lock at start.

Keep both cancellation calls outside the lock so synchronous stop can
wait for the worker to finish.

Fixes: 4e1a18bab124 ("can: rockchip_canfd: add hardware timestamping support")
Cc: stable@vger.kernel.org
Signed-off-by: Cunhao Lu <1579567540@qq.com>
---
 .../net/can/rockchip/rockchip_canfd-timestamp.c    | 34 +++++++++++++++++++---
 drivers/net/can/rockchip/rockchip_canfd.h          |  4 +++
 2 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/drivers/net/can/rockchip/rockchip_canfd-timestamp.c b/drivers/net/can/rockchip/rockchip_canfd-timestamp.c
index ad582afbbd68..0fa791849c95 100644
--- a/drivers/net/can/rockchip/rockchip_canfd-timestamp.c
+++ b/drivers/net/can/rockchip/rockchip_canfd-timestamp.c
@@ -30,18 +30,27 @@ static void rkcanfd_timestamp_work(struct work_struct *work)
 {
 	const struct delayed_work *delayed_work = to_delayed_work(work);
 	struct rkcanfd_priv *priv;
+	unsigned long flags;
 
 	priv = container_of(delayed_work, struct rkcanfd_priv, timestamp);
-	timecounter_read(&priv->tc);
-
-	schedule_delayed_work(&priv->timestamp, priv->work_delay_jiffies);
+	spin_lock_irqsave(&priv->timestamp_lock, flags);
+	if (priv->timestamp_active) {
+		timecounter_read(&priv->tc);
+
+		/* Serialize requeueing with timestamp_stop(). */
+		schedule_delayed_work(&priv->timestamp, priv->work_delay_jiffies);
+	}
+	spin_unlock_irqrestore(&priv->timestamp_lock, flags);
 }
 
 void rkcanfd_timestamp_work_init(struct rkcanfd_priv *priv)
 {
+	spin_lock_init(&priv->timestamp_lock);
+	priv->timestamp_active = false;
 	INIT_DELAYED_WORK(&priv->timestamp, rkcanfd_timestamp_work);
 }
 
+/* The caller must quiesce IRQs and timestamp work before reconfiguration. */
 void rkcanfd_timestamp_init(struct rkcanfd_priv *priv)
 {
 	const struct can_bittiming *dbt = &priv->can.fd.data_bittiming;
@@ -93,17 +102,34 @@ void rkcanfd_timestamp_init(struct rkcanfd_priv *priv)
 
 void rkcanfd_timestamp_start(struct rkcanfd_priv *priv)
 {
-	timecounter_init(&priv->tc, &priv->cc, ktime_get_real_ns());
+	unsigned long flags;
 
+	spin_lock_irqsave(&priv->timestamp_lock, flags);
+	timecounter_init(&priv->tc, &priv->cc, ktime_get_real_ns());
+	priv->timestamp_active = true;
 	schedule_delayed_work(&priv->timestamp, priv->work_delay_jiffies);
+	spin_unlock_irqrestore(&priv->timestamp_lock, flags);
 }
 
 void rkcanfd_timestamp_stop(struct rkcanfd_priv *priv)
 {
+	unsigned long flags;
+
+	spin_lock_irqsave(&priv->timestamp_lock, flags);
+	priv->timestamp_active = false;
+	spin_unlock_irqrestore(&priv->timestamp_lock, flags);
+
 	cancel_delayed_work(&priv->timestamp);
 }
 
 void rkcanfd_timestamp_stop_sync(struct rkcanfd_priv *priv)
 {
+	unsigned long flags;
+
+	spin_lock_irqsave(&priv->timestamp_lock, flags);
+	priv->timestamp_active = false;
+	spin_unlock_irqrestore(&priv->timestamp_lock, flags);
+
+	/* The worker needs timestamp_lock to finish. */
 	cancel_delayed_work_sync(&priv->timestamp);
 }
diff --git a/drivers/net/can/rockchip/rockchip_canfd.h b/drivers/net/can/rockchip/rockchip_canfd.h
index e1debab54534..2743c96ed42f 100644
--- a/drivers/net/can/rockchip/rockchip_canfd.h
+++ b/drivers/net/can/rockchip/rockchip_canfd.h
@@ -15,6 +15,7 @@
 #include <linux/netdevice.h>
 #include <linux/reset.h>
 #include <linux/skbuff.h>
+#include <linux/spinlock.h>
 #include <linux/timecounter.h>
 #include <linux/types.h>
 #include <linux/u64_stats_sync.h>
@@ -485,8 +486,11 @@ struct rkcanfd_priv {
 
 	struct cyclecounter cc;
 	struct timecounter tc;
+	/* Protects timestamp_active and worker reads/requeueing. */
+	spinlock_t timestamp_lock;
 	struct delayed_work timestamp;
 	unsigned long work_delay_jiffies;
+	bool timestamp_active;
 
 	struct can_berr_counter bec;
 

-- 
2.34.1

[PATCH net v5 5/6] can: rockchip_canfd: serialize TX with bus-off and restart

[Cunhao Lu via B4 Relay]

From: Cunhao Lu <1579567540@qq.com>

The bus-off path can reset the controller while ndo_start_xmit() is
active. CAN restart also flushes the echo ring before calling set_mode(),
so disabling TX in that callback is too late to protect echo slots.

Serialize TX submission, RX-side completion and retry with a private
lock and enabled flag. Disable TX and drain these users before publishing
CAN_STATE_BUS_OFF, protecting the core's echo flush during automatic and
manual recovery. Reject further submissions with NETDEV_TX_BUSY.

If close disables TX after an RX IRQ has consumed a self-transmitted
frame, skipping echo filtering alone would deliver it as ordinary RX.
Drop consumed FIFO entries while TX is disabled, checking under the same
lock, and continue draining the FIFO.

After draining the old IRQ and reinitializing the controller, restore
carrier, enable TX, resume IRQ handling and wake the queue under the
lock. This prevents the old bus-off IRQ from leaving manual recovery
with carrier off, while allowing a new bus-off to take precedence.

Keep shared IRQ handling suspended during open until initialization is
complete, and leave TX disabled on close or failed open. Keep resets and
synchronous IRQ/work draining outside the lock.

Fixes: b6661d73290c ("can: rockchip_canfd: add TX PATH")
Cc: stable@vger.kernel.org
Signed-off-by: Cunhao Lu <1579567540@qq.com>

---
Changes in v5:
- Drop consumed RX FIFO entries when tx_enabled is false under tx_lock,
  rather than skipping only echo filtering and delivering them as RX.
---
 drivers/net/can/rockchip/rockchip_canfd-core.c | 51 ++++++++++++++++++++++----
 drivers/net/can/rockchip/rockchip_canfd-rx.c   | 26 +++++++++----
 drivers/net/can/rockchip/rockchip_canfd-tx.c   | 16 +++++++-
 drivers/net/can/rockchip/rockchip_canfd.h      |  3 ++
 4 files changed, 80 insertions(+), 16 deletions(-)

diff --git a/drivers/net/can/rockchip/rockchip_canfd-core.c b/drivers/net/can/rockchip/rockchip_canfd-core.c
index 4b3db07242395..150748c0b6845 100644
--- a/drivers/net/can/rockchip/rockchip_canfd-core.c
+++ b/drivers/net/can/rockchip/rockchip_canfd-core.c
@@ -326,6 +326,35 @@ static void rkcanfd_chip_start(struct rkcanfd_priv *priv)
 		   rkcanfd_read(priv, RKCANFD_REG_MODE));
 }
 
+static void rkcanfd_tx_disable(struct rkcanfd_priv *priv)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&priv->tx_lock, flags);
+	priv->tx_enabled = false;
+	netif_stop_queue(priv->ndev);
+	spin_unlock_irqrestore(&priv->tx_lock, flags);
+}
+
+static void rkcanfd_chip_start_finish(struct rkcanfd_priv *priv)
+{
+	unsigned long flags;
+
+	/* Serialize carrier, IRQ enable and queue wake with a new bus-off. */
+	spin_lock_irqsave(&priv->tx_lock, flags);
+	/* A manual restart may have raced with the old bus-off IRQ's
+	 * netif_carrier_off(). That IRQ is now drained; restore carrier
+	 * before resuming IRQ handling so a new bus-off takes precedence.
+	 */
+	netif_carrier_on(priv->ndev);
+	priv->tx_enabled = true;
+	/* Publish the initialized state before resuming IRQ handling. */
+	smp_store_release(&priv->irq_suspended, false);
+	rkcanfd_chip_interrupts_enable(priv);
+	netif_wake_queue(priv->ndev);
+	spin_unlock_irqrestore(&priv->tx_lock, flags);
+}
+
 static void __rkcanfd_chip_stop(struct rkcanfd_priv *priv, const enum can_state state)
 {
 	priv->can.state = state;
@@ -357,6 +386,7 @@ static int rkcanfd_set_mode(struct net_device *ndev,
 
 	switch (mode) {
 	case CAN_MODE_START:
+		rkcanfd_tx_disable(priv);
 		rkcanfd_chip_interrupts_disable(priv);
 		/* Flush the interrupt mask write before suspending the handler. */
 		rkcanfd_read(priv, RKCANFD_REG_INT_MASK);
@@ -367,10 +397,7 @@ static int rkcanfd_set_mode(struct net_device *ndev,
 		rkcanfd_timestamp_stop_sync(priv);
 
 		rkcanfd_chip_start(priv);
-		/* Publish the initialized state before resuming IRQ handling. */
-		smp_store_release(&priv->irq_suspended, false);
-		rkcanfd_chip_interrupts_enable(priv);
-		netif_wake_queue(ndev);
+		rkcanfd_chip_start_finish(priv);
 		break;
 
 	default:
@@ -604,6 +631,12 @@ static int rkcanfd_handle_state_error_int(struct rkcanfd_priv *priv)
 	 * handles cf == NULL.
 	 */
 	skb = rkcanfd_alloc_can_err_skb(priv, &cf, &timestamp);
+	if (new_state == CAN_STATE_BUS_OFF) {
+		/* Drain TX before publishing BUS_OFF, which permits a manual
+		 * restart to flush echo SKBs before calling our set_mode().
+		 */
+		rkcanfd_tx_disable(priv);
+	}
 	can_change_state(ndev, cf, tx_state, rx_state);
 
 	if (new_state == CAN_STATE_BUS_OFF) {
@@ -749,6 +782,8 @@ static int rkcanfd_open(struct net_device *ndev)
 	if (err)
 		goto out_close_candev;
 
+	/* A shared IRQ may run as soon as request_irq() succeeds. */
+	WRITE_ONCE(priv->irq_suspended, true);
 	rkcanfd_chip_start(priv);
 	can_rx_offload_enable(&priv->offload);
 
@@ -756,13 +791,12 @@ static int rkcanfd_open(struct net_device *ndev)
 	if (err)
 		goto out_rkcanfd_chip_stop;
 
-	rkcanfd_chip_interrupts_enable(priv);
-
-	netif_start_queue(ndev);
+	rkcanfd_chip_start_finish(priv);
 
 	return 0;
 
 out_rkcanfd_chip_stop:
+	rkcanfd_tx_disable(priv);
 	can_rx_offload_disable(&priv->offload);
 	rkcanfd_chip_stop_sync(priv, CAN_STATE_STOPPED);
 	pm_runtime_put(ndev->dev.parent);
@@ -776,7 +810,7 @@ static int rkcanfd_stop(struct net_device *ndev)
 	struct rkcanfd_priv *priv = netdev_priv(ndev);
 
 	close_candev_cancel_restart_sync(ndev);
-	netif_stop_queue(ndev);
+	rkcanfd_tx_disable(priv);
 
 	rkcanfd_chip_interrupts_disable(priv);
 	free_irq(ndev->irq, priv);
@@ -939,6 +973,7 @@ static int rkcanfd_probe(struct platform_device *pdev)
 	priv->can.do_set_mode = rkcanfd_set_mode;
 	priv->can.do_get_berr_counter = rkcanfd_get_berr_counter;
 	priv->ndev = ndev;
+	spin_lock_init(&priv->tx_lock);
 
 	match = device_get_match_data(&pdev->dev);
 	if (match) {
diff --git a/drivers/net/can/rockchip/rockchip_canfd-rx.c b/drivers/net/can/rockchip/rockchip_canfd-rx.c
index 24e87daa1df00..5e64317d4eee6 100644
--- a/drivers/net/can/rockchip/rockchip_canfd-rx.c
+++ b/drivers/net/can/rockchip/rockchip_canfd-rx.c
@@ -91,6 +91,7 @@ rkcanfd_fifo_header_to_cfd_header(const struct rkcanfd_priv *priv,
 	return len + cfd->len;
 }
 
+/* Called with tx_lock held and TX enabled. */
 static int rkcanfd_rxstx_filter(struct rkcanfd_priv *priv,
 				const struct canfd_frame *cfd_rx, const u32 ts,
 				bool *tx_done)
@@ -204,7 +205,9 @@ static int rkcanfd_handle_rx_int_one(struct rkcanfd_priv *priv)
 	struct canfd_frame cfd[1] = { }, *skb_cfd;
 	struct rkcanfd_fifo_header header[1] = { };
 	struct sk_buff *skb;
+	unsigned long flags;
 	unsigned int len;
+	bool tx_done = false;
 	int err;
 
 	/* read header into separate struct and convert it later */
@@ -237,15 +240,24 @@ static int rkcanfd_handle_rx_int_one(struct rkcanfd_priv *priv)
 		return 0;
 	}
 
-	if (rkcanfd_get_tx_pending(priv)) {
-		bool tx_done = false;
+	/* Drop FIFO entries while TX is disabled, as they may be self-
+	 * received frames. Do not access the echo ring, retry TX or wake the
+	 * queue while restart owns the ring. The entry is already consumed.
+	 */
+	spin_lock_irqsave(&priv->tx_lock, flags);
+	if (unlikely(!priv->tx_enabled)) {
+		spin_unlock_irqrestore(&priv->tx_lock, flags);
+		return 0;
+	}
 
+	err = 0;
+	if (rkcanfd_get_tx_pending(priv))
 		err = rkcanfd_rxstx_filter(priv, cfd, header->ts, &tx_done);
-		if (err)
-			return err;
-		if (tx_done && !(priv->can.ctrlmode & CAN_CTRLMODE_LOOPBACK))
-			return 0;
-	}
+	spin_unlock_irqrestore(&priv->tx_lock, flags);
+	if (err)
+		return err;
+	if (tx_done && !(priv->can.ctrlmode & CAN_CTRLMODE_LOOPBACK))
+		return 0;
 
 	/* Manual handling of CAN Bus Error counters. See
 	 * rkcanfd_get_corrected_berr_counter() for detailed
diff --git a/drivers/net/can/rockchip/rockchip_canfd-tx.c b/drivers/net/can/rockchip/rockchip_canfd-tx.c
index 12200dcfd3389..f49ed6d2266d9 100644
--- a/drivers/net/can/rockchip/rockchip_canfd-tx.c
+++ b/drivers/net/can/rockchip/rockchip_canfd-tx.c
@@ -69,12 +69,19 @@ netdev_tx_t rkcanfd_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 	u32 reg_frameinfo, reg_id, reg_cmd;
 	unsigned int tx_head, frame_len;
 	const struct canfd_frame *cfd;
+	unsigned long flags;
 	int err;
 	u8 i;
 
 	if (can_dev_dropped_skb(ndev, skb))
 		return NETDEV_TX_OK;
 
+	spin_lock_irqsave(&priv->tx_lock, flags);
+	if (unlikely(!priv->tx_enabled)) {
+		netif_stop_queue(ndev);
+		goto out_busy;
+	}
+
 	if (!netif_subqueue_maybe_stop(priv->ndev, 0,
 				       rkcanfd_get_effective_tx_free(priv),
 				       RKCANFD_TX_STOP_THRESHOLD,
@@ -85,7 +92,7 @@ netdev_tx_t rkcanfd_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 				    priv->tx_head, priv->tx_tail,
 				    rkcanfd_get_tx_pending(priv));
 
-		return NETDEV_TX_BUSY;
+		goto out_busy;
 	}
 
 	cfd = (struct canfd_frame *)skb->data;
@@ -137,7 +144,14 @@ netdev_tx_t rkcanfd_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 				  RKCANFD_TX_STOP_THRESHOLD,
 				  RKCANFD_TX_START_THRESHOLD);
 
+	spin_unlock_irqrestore(&priv->tx_lock, flags);
+
 	return NETDEV_TX_OK;
+
+out_busy:
+	spin_unlock_irqrestore(&priv->tx_lock, flags);
+
+	return NETDEV_TX_BUSY;
 }
 
 void rkcanfd_handle_tx_done_one(struct rkcanfd_priv *priv, const u32 ts,
diff --git a/drivers/net/can/rockchip/rockchip_canfd.h b/drivers/net/can/rockchip/rockchip_canfd.h
index 2743c96ed42f0..4a2bdc205296e 100644
--- a/drivers/net/can/rockchip/rockchip_canfd.h
+++ b/drivers/net/can/rockchip/rockchip_canfd.h
@@ -476,6 +476,9 @@ struct rkcanfd_priv {
 	struct net_device *ndev;
 
 	void __iomem *regs;
+	/* Serialize TX submission/completion with bus-off and restart. */
+	spinlock_t tx_lock;
+	bool tx_enabled;
 	unsigned int tx_head;
 	unsigned int tx_tail;
 

-- 
2.34.1

[PATCH net v5 6/6] can: rockchip_canfd: serialize timecounter timestamp conversion

[Cunhao Lu via B4 Relay]

From: Cunhao Lu <1579567540@qq.com>

The timestamp worker advances the timecounter with timecounter_read()
while RX, TX completion and error-frame paths use timecounter_cyc2time()
to convert hardware timestamps without holding timestamp_lock.

timecounter_read() updates frac, cycle_last and nsec in separate steps.
A concurrent conversion can observe the new cycle_last with the old
nsec and produce an incorrect timestamp.

Hold timestamp_lock across timecounter_cyc2time(), using the same lock
as timecounter_read() and timecounter_init(). Keep the SKB timestamp
assignment outside the critical section.

TX completion nests timestamp_lock inside tx_lock; no timestamp-lock
holder acquires tx_lock.

Fixes: 4e1a18bab124 ("can: rockchip_canfd: add hardware timestamping support")
Cc: stable@vger.kernel.org
Signed-off-by: Cunhao Lu <1579567540@qq.com>
---
 drivers/net/can/rockchip/rockchip_canfd-timestamp.c | 5 ++++-
 drivers/net/can/rockchip/rockchip_canfd.h           | 4 ++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/net/can/rockchip/rockchip_canfd-timestamp.c b/drivers/net/can/rockchip/rockchip_canfd-timestamp.c
index 0fa791849c95..05f1005ee506 100644
--- a/drivers/net/can/rockchip/rockchip_canfd-timestamp.c
+++ b/drivers/net/can/rockchip/rockchip_canfd-timestamp.c
@@ -15,13 +15,16 @@ static u64 rkcanfd_timestamp_read(struct cyclecounter *cc)
 	return rkcanfd_get_timestamp(priv);
 }
 
-void rkcanfd_skb_set_timestamp(const struct rkcanfd_priv *priv,
+void rkcanfd_skb_set_timestamp(struct rkcanfd_priv *priv,
 			       struct sk_buff *skb, const u32 timestamp)
 {
 	struct skb_shared_hwtstamps *hwtstamps = skb_hwtstamps(skb);
+	unsigned long flags;
 	u64 ns;
 
+	spin_lock_irqsave(&priv->timestamp_lock, flags);
 	ns = timecounter_cyc2time(&priv->tc, timestamp);
+	spin_unlock_irqrestore(&priv->timestamp_lock, flags);
 
 	hwtstamps->hwtstamp = ns_to_ktime(ns);
 }
diff --git a/drivers/net/can/rockchip/rockchip_canfd.h b/drivers/net/can/rockchip/rockchip_canfd.h
index 4a2bdc205296..63f146ff8e6b 100644
--- a/drivers/net/can/rockchip/rockchip_canfd.h
+++ b/drivers/net/can/rockchip/rockchip_canfd.h
@@ -489,7 +489,7 @@ struct rkcanfd_priv {
 
 	struct cyclecounter cc;
 	struct timecounter tc;
-	/* Protects timestamp_active and worker reads/requeueing. */
+	/* Protects tc, timestamp_active and worker requeueing. */
 	spinlock_t timestamp_lock;
 	struct delayed_work timestamp;
 	unsigned long work_delay_jiffies;
@@ -557,7 +557,7 @@ void rkcanfd_ethtool_init(struct rkcanfd_priv *priv);
 
 int rkcanfd_handle_rx_int(struct rkcanfd_priv *priv);
 
-void rkcanfd_skb_set_timestamp(const struct rkcanfd_priv *priv,
+void rkcanfd_skb_set_timestamp(struct rkcanfd_priv *priv,
 			       struct sk_buff *skb, const u32 timestamp);
 void rkcanfd_timestamp_work_init(struct rkcanfd_priv *priv);
 void rkcanfd_timestamp_init(struct rkcanfd_priv *priv);

-- 
2.34.1

Re: [PATCH net v5 1/6] can: dev: prevent bus-off recovery when the interface is not running

[netdev-bot+sashiko]

Thank you for your contribution! Sashiko AI review found 1 potential
issue(s) to consider.

Critical: 0 · High: 0 (1) · Medium: 1 · Low: 0

If you believe none of the issues are legitimate, please reply to each
issue of Medium severity or higher and explain why the AI is wrong.
If any of them are legitimate and you plan to respin, please let patchwork
know by including "pw-bot: cr" as a separate line at the end of your reply
(one such reply per series is enough).

- [Medium] In can_restart() (drivers/net/can/dev/dev.c), the new
  netif_running() check is lockless and is not serialized with…

Pre-existing issues:
- [High] can_bus_off() (drivers/net/can/dev/dev.c:270-282) reads
  netif_running() into `restart` and only later calls…

--

can: dev: prevent bus-off recovery when the interface is not running

This commit adds a netif_running() check to can_restart(), so a bus-off
restart is skipped when the interface is not running. It also changes
can_bus_off() to schedule restart_work only when restart_ms is set and
the interface is running.

> diff --git a/drivers/net/can/dev/dev.c b/drivers/net/can/dev/dev.c
> index 769745e22a3c7..92492c503446e 100644
> --- a/drivers/net/can/dev/dev.c
> +++ b/drivers/net/can/dev/dev.c
> @@ -198,6 +198,9 @@ static int can_restart(struct net_device *dev)
>  	if (!priv->do_set_mode)
>  		return -EOPNOTSUPP;
>  
> +	if (!netif_running(dev))
> +		return -ENETDOWN;
> +

[Severity: Medium]
Is this check enough to deliver what the subject line promises? It reads
the running bit once without any lock. can_restart_work() runs on the
system workqueue without RTNL or any CAN-private lock, so nothing orders
it against __dev_close_many() and ndo_stop().

The commit message describes the problem as:

  "Recovery can therefore be queued or started after the interface has
  begun closing, potentially re-enabling hardware while the driver is
  tearing it down."

That still seems possible if the work passes this check just before
__dev_close_many() clears __LINK_STATE_START:

restart_work                          ip link set canX down
can_restart()
  netif_running() == true
                                      __dev_close_many()
                                        clear_bit(__LINK_STATE_START)
                                        ndo_stop() -> sja1000_close()
                                          set_reset_mode(dev);
                                          free_irq(dev->irq, dev);
  can_flush_echo_skb()
  netif_rx(skb)
  netif_carrier_on()
  priv->do_set_mode(dev, CAN_MODE_START)
                                          close_candev()
                                            cancel_delayed_work_sync()

cancel_delayed_work_sync() in close_candev() waits for the work to
finish, but it does not undo the restart. The controller ends up in
operating mode with interrupts enabled and no IRQ handler registered.
The carrier is also on while the interface is down.

With a shared IRQ line, could this cause an unhandled interrupt storm
and get the line disabled for other devices? On runtime-PM drivers, can
do_set_mode() touch registers after the clocks have been cut?

Many drivers (sja1000, cc770, at91, c_can, flexcan, sun4i, ti_hecc and
others) reset the chip and free the IRQ before they call close_candev().
Later in the series, close_candev_cancel_restart_sync() is added and
called early in ndo_stop(), but only for rockchip_canfd ("can:
rockchip_canfd: cancel bus-off restart before closing the device").

Should the other drivers get the same change? Or could the core
serialize this so the window is closed for every driver?

> @@ -264,8 +267,9 @@ int can_restart_now(struct net_device *dev)
>  void can_bus_off(struct net_device *dev)
>  {
>  	struct can_priv *priv = netdev_priv(dev);
> +	const bool restart = priv->restart_ms && netif_running(dev);
>  
> -	if (priv->restart_ms)
> +	if (restart)
>  		netdev_info(dev, "bus-off, scheduling restart in %d ms\n",
>  			    priv->restart_ms);
>  	else
> @@ -273,7 +277,7 @@ void can_bus_off(struct net_device *dev)
>  
>  	netif_carrier_off(dev);
>  
> -	if (priv->restart_ms)
> +	if (restart)
>  		schedule_delayed_work(&priv->restart_work,
>  				      msecs_to_jiffies(priv->restart_ms));
>  }

[Severity: High]
This is a pre-existing issue and was not introduced by this patch. The
patch makes the window smaller, but can restart_work still be queued
after close_candev() has cancelled it?

restart is read before netdev_info() and netif_carrier_off() run.
Nothing ties that read to the later schedule_delayed_work(), or to the
single cancel_delayed_work_sync() in close_candev().

Some drivers call close_candev() before they stop their bus-off
producer. mcp251x_stop() is one example:

drivers/net/can/spi/mcp251x.c:mcp251x_stop() {
	...
	close_candev(net);

	priv->force_quit = 1;
	free_irq(spi->irq, priv);
	...
}

Meanwhile the threaded IST, mcp251x_can_ist(), calls can_bus_off().
hi3110_stop(), mscan_close(), peak_usb_ndo_stop() and f81604_close()
use the same order.

One possible sequence:

mcp251x_can_ist()                     unregister / ifdown
  can_bus_off()
    restart = true
    <preempted>
                                      __dev_close_many()
                                        clear_bit(__LINK_STATE_START)
                                        mcp251x_stop()
                                          close_candev()
                                            cancel_delayed_work_sync()
                                          free_irq()  /* waits for IST */
    netif_carrier_off()
    schedule_delayed_work(&priv->restart_work, ...)

After that, nothing cancels the work. free_candev() is only:

void free_candev(struct net_device *dev)
{
	free_netdev(dev);
}

unregister_candev() does not touch restart_work either. On driver unbind
or USB unplug, the device can be freed before restart_ms expires. Would
the pending delayed_work timer and work item then sit inside freed
netdev_priv memory?

The device might instead be reopened before the work runs. __dev_open()
sets __LINK_STATE_START before ndo_open(), and open_candev() does not
cancel the work. Would the stale work then pass the new netif_running()
check in can_restart() and call do_set_mode(CAN_MODE_START) while the
driver's own open sequence is running?

The series does not add a cancel in free_candev() or unregister_candev().
Would cancelling or disabling restart_work there close this window?

-- 
Sashiko AI review · https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20261015-rockchip-canfd-restart-close-v5-0-ae77327037c9%40qq.com

Re: [PATCH net v5 2/6] can: dev: add close_candev_cancel_restart_sync()

[netdev-bot+sashiko]

Thank you for your contribution! Sashiko AI review found more severe
issue(s) in other patches of this series. This mail is only an FYI, in case
you want to address the nit picks below when you respin.

Low priority / nit picks for your consideration:

- [Low] Concern: close_candev_cancel_restart_sync() is added to
  include/linux/can/dev.h, but the only call site is a no-op refactor in…
- [Low] Concern: the commit has 'Cc: stable@vger.kernel.org' but no
  Fixes: tag and no '# prerequisite for ...' note, while being a no-op…

--

can: dev: add close_candev_cancel_restart_sync()

This adds an inline helper, close_candev_cancel_restart_sync(), to
include/linux/can/dev.h. It only cancels the bus-off restart work, so
drivers can cancel it before tearing down IRQ and hardware resources.
close_candev() now uses the helper and keeps its existing order: cancel
the restart work, then flush the echo skbs.

> Use the helper in close_candev(), preserving its existing cancellation
> and echo cleanup order.
>
> Cc: stable@vger.kernel.org

[Severity: Low]
This isn't a bug, but could the commit message say why this is going to
stable?

On its own, the patch is a no-op refactor of close_candev() plus a new
helper. It has no Fixes: tag and no "# prerequisite for ..." annotation.

The only new user seems to be the next patch in the series, "can:
rockchip_canfd: cancel bus-off restart before closing the device". That
patch has its own Fixes: ff60bfbaf67f and Cc: stable.

Would it help backporters to mark this patch as a prerequisite for that
fix? If the rockchip fix were picked without it, the build would fail
rather than the code misbehaving, so this only affects commit metadata.

> diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
> index 6d0710d6f571d..a277d12332f15 100644
> --- a/include/linux/can/dev.h
> +++ b/include/linux/can/dev.h

[ ... ]

> @@ -115,6 +116,17 @@ struct can_priv *safe_candev_priv(struct net_device *dev);
>  
>  int open_candev(struct net_device *dev);
>  void close_candev(struct net_device *dev);
> +
> +/* Cancel bus-off restart before tearing down resources used by the restart
> + * callback. The driver must still call close_candev() for the final cleanup.
> + */
> +static inline void close_candev_cancel_restart_sync(struct net_device *dev)
> +{
> +	struct can_priv *priv = netdev_priv(dev);
> +
> +	cancel_delayed_work_sync(&priv->restart_work);
> +}

[Severity: Low]
In this patch, the only caller of close_candev_cancel_restart_sync() is
close_candev() in drivers/net/can/dev/dev.c, and that conversion keeps
the old behaviour. As a result, no driver's ndo_stop gets the early
cancellation that the commit message describes.

Is the helper meant to be used only by later patches?

This looks resolved later in the series. In "can: rockchip_canfd: cancel
bus-off restart before closing the device", rkcanfd_stop() calls the
helper first:

	close_candev_cancel_restart_sync(ndev);
	rkcanfd_tx_disable(priv);

	rkcanfd_chip_interrupts_disable(priv);
	free_irq(ndev->irq, priv);

It then calls close_candev() after the IRQ teardown.

Could the commit message mention that user, so the helper doesn't look
unused when this patch is reviewed alone?

-- 
Sashiko AI review · https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20261015-rockchip-canfd-restart-close-v5-0-ae77327037c9%40qq.com

Re: [PATCH net v5 5/6] can: rockchip_canfd: serialize TX with bus-off and restart

[netdev-bot+sashiko]

Thank you for your contribution! Sashiko AI review found more severe
issue(s) in other patches of this series. This mail is only an FYI, in case
you want to address the nit picks below when you respin.

Low priority / nit picks for your consideration:

- [Low] This patch takes spin_lock_irqsave(&priv->tx_lock, flags) near
  the top of rkcanfd_start_xmit()…

Pre-existing issues:
- [Medium] This problem wasn't introduced by this patch, but
  rkcanfd_start_xmit() does not handle a can_put_echo_skb() failure.

--

can: rockchip_canfd: serialize TX with bus-off and restart

This adds a private tx_lock and tx_enabled flag. They serialize
rkcanfd_start_xmit() and the RX-side echo completion and retry against
bus-off handling and CAN restart. TX is disabled before CAN_STATE_BUS_OFF
is published, and carrier, TX, IRQs and the queue are re-enabled together
under the lock after the controller has been reinitialized.

> diff --git a/drivers/net/can/rockchip/rockchip_canfd-tx.c b/drivers/net/can/rockchip/rockchip_canfd-tx.c
> index 12200dcfd3389..f49ed6d2266d9 100644
> --- a/drivers/net/can/rockchip/rockchip_canfd-tx.c
> +++ b/drivers/net/can/rockchip/rockchip_canfd-tx.c
> @@ -69,12 +69,19 @@ netdev_tx_t rkcanfd_start_xmit(struct sk_buff *skb, struct net_device *ndev)

[ ... ]

>  	if (can_dev_dropped_skb(ndev, skb))
>  		return NETDEV_TX_OK;
>  
> +	spin_lock_irqsave(&priv->tx_lock, flags);
> +	if (unlikely(!priv->tx_enabled)) {
> +		netif_stop_queue(ndev);
> +		goto out_busy;
> +	}
> +

[Severity: Low]
This lock stays held with hard IRQs disabled until the end of
rkcanfd_start_xmit(). The locked region includes the echo skb handling:

drivers/net/can/rockchip/rockchip_canfd-tx.c:rkcanfd_start_xmit() {
    ...
	frame_len = can_skb_get_frame_len(skb);
	err = can_put_echo_skb(skb, ndev, tx_head, frame_len);
	if (!err)
		netdev_sent_queue(priv->ndev, frame_len);
    ...
}

can_put_echo_skb()->can_create_echo_skb() clones the skb and then calls
consume_skb() on the original. If the clone fails, it calls kfree_skb()
instead. can_put_echo_skb() also calls kfree_skb() in three cases: IFF_ECHO
is clear, the protocol check fails, or the echo slot is still occupied.

Freeing the original skb runs the socket destructor (sock_wfree()). If this
is the last TX skb of a closed socket, that can continue into __sk_free().

The comment above dev_kfree_skb_irq() in include/linux/netdevice.h says
kfree_skb() and consume_skb() must not be called with hardware interrupts
disabled. Before this patch, ndo_start_xmit() ran with only BH disabled.

Nothing seems to fail visibly today. skb_release_head_state() only warns
on in_hardirq(), not on irqs_disabled(), and peak_canfd uses a similar
pattern. Even so, should the clone and the free of the original skb happen
outside tx_lock, with only the echo slot pointer and tx_head published
under the lock?

[ ... ]

> @@ -137,7 +144,14 @@ netdev_tx_t rkcanfd_start_xmit(struct sk_buff *skb, struct net_device *ndev)
>  				  RKCANFD_TX_STOP_THRESHOLD,
>  				  RKCANFD_TX_START_THRESHOLD);
>  
> +	spin_unlock_irqrestore(&priv->tx_lock, flags);
> +
>  	return NETDEV_TX_OK;

[Severity: Medium]
This is a pre-existing issue that this patch did not introduce. What
happens when can_put_echo_skb() fails earlier in this function?

If the GFP_ATOMIC clone in can_create_echo_skb() fails, can_put_echo_skb()
frees the original skb and returns -ENOMEM. That leaves
priv->can.echo_skb[tx_head] set to NULL. In that case rkcanfd_start_xmit()
only skips netdev_sent_queue():

	err = can_put_echo_skb(skb, ndev, tx_head, frame_len);
	if (!err)
		netdev_sent_queue(priv->ndev, frame_len);

	WRITE_ONCE(priv->tx_head, priv->tx_head + 1);

	rkcanfd_start_xmit_write_cmd(priv, reg_cmd);

When the self-received frame comes back, rkcanfd_handle_rx_int_one() sees
tx_pending != 0 and calls rkcanfd_rxstx_filter(). That function then hits
the NULL slot:

drivers/net/can/rockchip/rockchip_canfd-rx.c:rkcanfd_rxstx_filter() {
    ...
	skb = priv->can.echo_skb[tx_tail];
	if (!skb) {
		netdev_err(priv->ndev, ...);

		return -ENOMSG;
	}
    ...
}

tx_tail never advances, because the only normal advance happens after a
successful echo match. rkcanfd_handle_rx_int() also stops draining the
FIFO when it gets the error.

After that, does every RX IRQ consume and drop one FIFO entry with another
-ENOMSG? TX would then stall once the ring is full, until a bus-off
restart or an interface down/up reinitializes the controller.

This patch keeps the same error propagation in rkcanfd_handle_rx_int_one().

-- 
Sashiko AI review · https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20261015-rockchip-canfd-restart-close-v5-0-ae77327037c9%40qq.com

Re: [PATCH net v5 1/6] can: dev: prevent bus-off recovery when the interface is not running

[Cunhao Lu]

Hi,

> [Severity: Medium]
> Is this check enough to deliver what the subject line promises? It reads
> the running bit once without any lock. can_restart_work() runs on the
> system workqueue without RTNL or any CAN-private lock, so nothing orders
> it against __dev_close_many() and ndo_stop().

The check alone does not serialize restart with ndo_stop(), as noted in
the commit message. For Rockchip, this series also calls
close_candev_cancel_restart_sync() at the beginning of rkcanfd_stop(),
while the resources are still available, to wait for any restart that
has already passed the check before tearing down the hardware and IRQ.
The pre-existing teardown races in other drivers are outside the scope
of this series and should be addressed in separate patches.

> [Severity: High]
> This is a pre-existing issue and was not introduced by this patch. The
> patch makes the window smaller, but can restart_work still be queued
> after close_candev() has cancelled it?

Yes, if a bus-off producer is still running, the check does not prevent
it from queuing work after cancellation. For Rockchip, the series keeps
the final close_candev() after free_irq() has drained the bus-off
producer. This final cancellation catches work queued after the early
cancellation, and the running check prevents such work from restarting
the hardware while the interface is down.

The late-enqueue and lifetime issues in other drivers should also be
handled in separate patches. This series is limited to the Rockchip
CAN-FD restart/close races and does not add a generic free/unregister
safeguard.

Regards,
Cunhao Lu

Re: [PATCH net v5 2/6] can: dev: add close_candev_cancel_restart_sync()

[Cunhao Lu]

Hi,

> [Severity: Low]
> This isn't a bug, but could the commit message say why this is going to
> stable?
>
> On its own, the patch is a no-op refactor of close_candev() plus a new
> helper. It has no Fixes: tag and no "# prerequisite for ..." annotation.

This patch is a prerequisite for the next patch, "can: rockchip_canfd:
cancel bus-off restart before closing the device".

> [Severity: Low]
> In this patch, the only caller of close_candev_cancel_restart_sync() is
> close_candev() in drivers/net/can/dev/dev.c, and that conversion keeps
> the old behaviour. As a result, no driver's ndo_stop gets the early
> cancellation that the commit message describes.
> ...
> Could the commit message mention that user, so the helper doesn't look
> unused when this patch is reviewed alone?

Yes. The following Rockchip patch is the intended user. The current
commit message explains why drivers need the helper, but does not
explicitly name that user. The conversion of close_candev() intentionally
preserves its existing behaviour.

If v6 is needed, I will update the commit message to clarify this.

Regards,
Cunhao Lu

Re: [PATCH net v5 5/6] can: rockchip_canfd: serialize TX with bus-off and restart

[Cunhao Lu]

Hi,

> [Severity: Low]
> This lock stays held with hard IRQs disabled until the end of
> rkcanfd_start_xmit(). The locked region includes the echo skb handling:
> 
> drivers/net/can/rockchip/rockchip_canfd-tx.c:rkcanfd_start_xmit() {
>     ...
> frame_len = can_skb_get_frame_len(skb);
> err = can_put_echo_skb(skb, ndev, tx_head, frame_len);
> if (!err)
> netdev_sent_queue(priv->ndev, frame_len);
>     ...
> }
> 
> can_put_echo_skb()->can_create_echo_skb() clones the skb and then calls
> consume_skb() on the original. If the clone fails, it calls kfree_skb()
> instead. can_put_echo_skb() also calls kfree_skb() in three cases: IFF_ECHO
> is clear, the protocol check fails, or the echo slot is still occupied.
> 
> Freeing the original skb runs the socket destructor (sock_wfree()). If this
> is the last TX skb of a closed socket, that can continue into __sk_free().
> 
> The comment above dev_kfree_skb_irq() in include/linux/netdevice.h says
> kfree_skb() and consume_skb() must not be called with hardware interrupts
> disabled. Before this patch, ndo_start_xmit() ran with only BH disabled.

You are right. On non-PREEMPT_RT kernels, the new locking places the
original skb's release inside an IRQ-disabled section. I will fix this
in the next revision while preserving the synchronization with bus-off
and close.

> [Severity: Medium]
> This is a pre-existing issue that this patch did not introduce. What
> happens when can_put_echo_skb() fails earlier in this function?

Yes, the existing code still advances tx_head and submits the frame after
echo allocation fails. When tx_tail reaches the empty slot, completion
matching fails and tx_tail cannot advance, which can stall TX.

This predates the series. I have recorded it as a separate follow-up fix
and will keep it outside this restart/close series.

Regards,
Cunhao Lu

pw-bot: cr