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

Heiko Stübner
2023-12-06T09:30:15Z

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@friendlyarm.com>

Reviewed-by: Heiko Stuebner <heiko@sntech.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) {
>