linux-kernel - Re: [PATCH] i2c: rk3x: fix potential spinlock recursion on poll

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Message-ID: <5298230.31r3eYUQgx@diego>
Date:   Wed, 06 Dec 2023 10:29:51 +0100
From:   Heiko Stübner <heiko@...ech.de>
To:     Andi Shyti <andi.shyti@...nel.org>,
        Jensen Huang <jensenhuang@...endlyarm.com>
Cc:     Jensen Huang <jensenhuang@...endlyarm.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: rk3x: fix potential spinlock recursion on poll

Am Mittwoch, 6. Dezember 2023, 10:06:40 CET schrieb Jensen Huang:
> Possible deadlock scenario (on reboot):
> rk3x_i2c_xfer_common(polling)
>     -> rk3x_i2c_wait_xfer_poll()
>         -> rk3x_i2c_irq(0, i2c);
>             --> spin_lock(&i2c->lock);
>             ...
>         <rk3x i2c interrupt>
>         -> rk3x_i2c_irq(0, i2c);
>             --> spin_lock(&i2c->lock); (deadlock here)
>
> Store the IRQ number and disable/enable it around the polling transfer.
> This patch has been tested on NanoPC-T4.
> 
> Signed-off-by: Jensen Huang <jensenhuang@...endlyarm.com>

Reviewed-by: Heiko Stuebner <heiko@...ech.de>


> ---
>  drivers/i2c/busses/i2c-rk3x.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c
> index a044ca0c35a1..94514637c3bd 100644
> --- a/drivers/i2c/busses/i2c-rk3x.c
> +++ b/drivers/i2c/busses/i2c-rk3x.c
> @@ -200,6 +200,7 @@ struct rk3x_i2c {
>  	struct clk *clk;
>  	struct clk *pclk;
>  	struct notifier_block clk_rate_nb;
> +	int irq;
>  
>  	/* Settings */
>  	struct i2c_timings t;
> @@ -1087,13 +1088,18 @@ static int rk3x_i2c_xfer_common(struct i2c_adapter *adap,
>  
>  		spin_unlock_irqrestore(&i2c->lock, flags);
>  
> -		rk3x_i2c_start(i2c);
> -
>  		if (!polling) {
> +			rk3x_i2c_start(i2c);
> +
>  			timeout = wait_event_timeout(i2c->wait, !i2c->busy,
>  						     msecs_to_jiffies(WAIT_TIMEOUT));
>  		} else {
> +			disable_irq(i2c->irq);
> +			rk3x_i2c_start(i2c);
> +
>  			timeout = rk3x_i2c_wait_xfer_poll(i2c);
> +
> +			enable_irq(i2c->irq);
>  		}
>  
>  		spin_lock_irqsave(&i2c->lock, flags);
> @@ -1310,6 +1316,8 @@ static int rk3x_i2c_probe(struct platform_device *pdev)
>  		return ret;
>  	}
>  
> +	i2c->irq = irq;
> +
>  	platform_set_drvdata(pdev, i2c);
>  
>  	if (i2c->soc_data->calc_timings == rk3x_i2c_v0_calc_timings) {
>