[PATCH net v2 2/2] net: spacemit: Hold RTNL lock in emac_resume() and emac_suspend()

[Muhammad Bilal]

Taking RTNL before the netif_running() checks is the important part
of v2, otherwise the check would race with a concurrent close.
Depends on patch 1, as noted.

Reviewed-by: Muhammad Bilal <meatuni001 at gmail.com>

On Fri, Nov 13, 2026 at 6:28 PM Ali Tariq <alitariq45892 at gmail.com> wrote:
>
> The emac_resume() calls the emac_open() and emac_suspend() calls
> emac_stop() functions directly without holding the lock through
> rtnl_lock(). These functions rely on phy_disconnect() which reads pointer
> with rtnl_dereference(). But since no lock is being held,
> rtnl_dereference throws a suspicious RCU usage on
> Orange Pi RV2 (SpacemiT K1) warning when lockdep is enabled.
>
> WARNING: suspicious RCU usage
> drivers/net/phy/phy_device.c:1831 suspicious rcu_dereference_protected() usage!
> Call Trace:
> phy_detach_internal+0x490/0x5f2
> phy_disconnect+0x90/0xc0
> emac_stop+0x114/0x626
> emac_suspend+0xac/0x126
> platform_pm_suspend+0x72/0xe4
>
> Take RTNL in emac_suspend() and emac_resume() before the netif_running()
> checks, so the interface can't be opened or closed between the check and
> emac_stop() or emac_open().
>
> Found by CI suspend tests on Orange Pi RV2 (SpacemiT K1). Tested on the
> same board with lockdep enabled: 12 suspend/resume cycles without the
> warning, and kselftest with no new failures.
>
> Fixes: bfec6d7f2001 ("net: spacemit: Add K1 Ethernet MAC")
> Signed-off-by: Ali Tariq <alitariq45892 at gmail.com>
> ---
> Changes in v2:
> - Moved the rtnl_lock() before the 'running' flag check
> Warning Log: https://kernelci.cloud-v.co/scheduler/job/549#L2168
> Fixed Log: https://kernelci.cloud-v.co/scheduler/job/589
> ---
>  drivers/net/ethernet/spacemit/k1_emac.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/spacemit/k1_emac.c b/drivers/net/ethernet/spacemit/k1_emac.c
> index 51edc95f54c8..d07d8a1aa5ee 100644
> --- a/drivers/net/ethernet/spacemit/k1_emac.c
> +++ b/drivers/net/ethernet/spacemit/k1_emac.c
> @@ -2031,11 +2031,16 @@ static int emac_resume(struct device *dev)
>                 dev_err(dev, "Failed to enable bus clock: %d\n", ret);
>                 return ret;
>         }
> +       rtnl_lock();
>
> -       if (!netif_running(ndev))
> +       if (!netif_running(ndev)) {
> +               rtnl_unlock();
>                 return 0;
> +       }
>
>         ret = emac_open(ndev);
> +       rtnl_unlock();
> +
>         if (ret) {
>                 clk_disable_unprepare(priv->bus_clk);
>                 return ret;
> @@ -2055,12 +2060,16 @@ static int emac_suspend(struct device *dev)
>
>         disable_work_sync(&priv->tx_timeout_task);
>
> +       rtnl_lock();
> +
>         if (!ndev || !netif_running(ndev)) {
> +               rtnl_unlock();
>                 clk_disable_unprepare(priv->bus_clk);
>                 return 0;
>         }
>
>         emac_stop(ndev);
> +       rtnl_unlock();
>
>         clk_disable_unprepare(priv->bus_clk);
>         netif_device_detach(ndev);
> --
> 2.34.1
>