Re: [PATCH can] can: rockchip: rk3576: fix rtnl_lock deadlock during interface down under bus traffic

[Marc Kleine-Budde]

On 17.08.2026 09:37:50, Cheng Liu wrote:
> When bringing the CAN interface down (via `ip link set can0 down`) while
> there is heavy incoming CAN traffic or continuous hardware error frames,
> the system hangs and deadlocks. Existing and new networking operations
> (such as `ifconfig`, SSH logins, Socket operations) hang indefinitely
> waiting for `rtnl_lock`.
>
> The deadlock occurs because `rk3576_canfd_close()` calls `napi_disable()`
> before `rk3576_canfd_stop()`. Since hardware interrupts are still
> active, incoming CAN frames and error interrupts continuously trigger
> `napi_schedule()`, preventing `napi_disable()` from seeing the
> `NAPI_STATE_SCHED` bit cleared and causing it to loop infinitely in
> `msleep(1)`. Because `dev_close()` holds the global `rtnl_lock`, the
> entire networking subsystem deadlocks:
>
> Call trace:
>   __switch_to+0xdc/0x120
>   __schedule+0x2ac/0x840
>   schedule+0x54/0xe0
>   schedule_hrtimeout_range_clock+0x98/0x134
>   usleep_range_state+0x7c/0xb0
>   napi_disable+0xc0/0x110
>   rk3576_canfd_close+0x44/0xd0
>   __dev_close_many+0xb0/0x14c
>   dev_change_flags+0x28/0x64
>   do_setlink+0x618/0xe2c
>   rtnetlink_rcv_msg+0x2a8/0x380
>
> Fix this by:
> 1. Reordering `rk3576_canfd_close()` to call `rk3576_canfd_stop()` before
>    `napi_disable()`, ensuring interrupts are disabled and controller is
>    in reset mode before waiting for NAPI to complete.
> 2. Standardizing `rk3576_canfd_rx_poll()` to respect the NAPI
>    quota/budget and properly complete NAPI polling via
>    `napi_complete_done()`.
> 3. Guarding against NULL pointer dereference in `rk3576_canfd_err()` when
>    `alloc_can_err_skb()` fails, and calling `can_bus_off()` upon bus-off.
>
> Signed-off-by: Cheng Liu <chengliu480@xxxxxxxxx>
> ---
>  drivers/net/can/rockchip/rk3576_canfd.c | 61 +++++++++++++------------

The driver for the rk3576 is not mainline, yet. Maybe Elaine can pick it
up.

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
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