netdev - Re: [PATCH net] r8169: fix deadlock on RTL8125 in jumbo mtu mode

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Message-ID: <c66a65f0-7d45-4bdd-9387-9f0b8bb06eef@gmail.com>
Date: Sun, 26 Nov 2023 21:14:24 +0100
From: Heiner Kallweit <hkallweit1@...il.com>
To: Realtek linux nic maintainers <nic_swsd@...ltek.com>,
 Jakub Kicinski <kuba@...nel.org>, David Miller <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
 Ian Chen <free122448@...mail.com>
Subject: Re: [PATCH net] r8169: fix deadlock on RTL8125 in jumbo mtu mode

On 26.11.2023 19:36, Heiner Kallweit wrote:
> The original change results in a deadlock if jumbo mtu mode is used.
> Reason is that the phydev lock is held when rtl_reset_work() is called
> here, and rtl_jumbo_config() calls phy_start_aneg() which also tries
> to acquire the phydev lock. Fix this by calling rtl_reset_work()
> asynchronously.
> 
> Fixes: 621735f59064 ("r8169: fix rare issue with broken rx after link-down on RTL8125")
> Reported-by: Ian Chen <free122448@...mail.com>
> Tested-by: Ian Chen <free122448@...mail.com>
> Cc: stable@...r.kernel.org
> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
> ---
>  drivers/net/ethernet/realtek/r8169_main.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
> index 0ee3579ce..e32cc3279 100644
> --- a/drivers/net/ethernet/realtek/r8169_main.c
> +++ b/drivers/net/ethernet/realtek/r8169_main.c
> @@ -575,6 +575,7 @@ struct rtl8169_tc_offsets {
>  enum rtl_flag {
>  	RTL_FLAG_TASK_ENABLED = 0,
>  	RTL_FLAG_TASK_RESET_PENDING,
> +	RTL_FLAG_TASK_RESET_NO_QUEUE_WAKE,
>  	RTL_FLAG_TASK_TX_TIMEOUT,
>  	RTL_FLAG_MAX
>  };
> @@ -4494,6 +4495,8 @@ static void rtl_task(struct work_struct *work)
>  reset:
>  		rtl_reset_work(tp);
>  		netif_wake_queue(tp->dev);
> +	} else if (test_and_clear_bit(RTL_FLAG_TASK_RESET_NO_QUEUE_WAKE, tp->wk.flags)) {
> +		rtl_reset_work(tp);
>  	}
>  out_unlock:
>  	rtnl_unlock();
> @@ -4527,7 +4530,7 @@ static void r8169_phylink_handler(struct net_device *ndev)
>  	} else {
>  		/* In few cases rx is broken after link-down otherwise */
>  		if (rtl_is_8125(tp))
> -			rtl_reset_work(tp);
> +			rtl_schedule_task(tp, RTL_FLAG_TASK_RESET_NO_QUEUE_WAKE);
>  		pm_runtime_idle(d);
>  	}
>  

I noticed there's a potential issue with my approach.
So I have to rework this, please do not apply.