linux-kernel - Re: [PATCH v2] i2c: avoid sleep in IRQ context

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Date:   Wed, 14 Aug 2019 12:07:56 +0200
From:   Wolfram Sang <wsa@...-dreams.de>
To:     Fuqian Huang <huangfq.daxian@...il.com>,
        Russell King <linux@...linux.org.uk>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] i2c: avoid sleep in IRQ context

On Wed, Aug 07, 2019 at 03:18:07PM +0800, Fuqian Huang wrote:
> i2c_pxa_handler -> i2c_pxa_irq_txempty ->
> i2c_pxa_reset -> i2c_pxa_set_slave -> i2c_pxa_wait_slave
> 
> As i2c_pxa_handler is an interrupt handler, it will finally
> calls i2c_pxa_wait_slave which calls msleep.
> 
> Add in_interrupt check before msleep to avoid sleep
> in IRQ context.
> When in interrupt context, use mdelay instead of msleep.
> 
> Signed-off-by: Fuqian Huang <huangfq.daxian@...il.com>

Adding RMK to CC because he is the PXA I2C slave user I know of.

> ---
>  drivers/i2c/busses/i2c-pxa.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-pxa.c b/drivers/i2c/busses/i2c-pxa.c
> index 2c3c3d6935c0..876e693bafd9 100644
> --- a/drivers/i2c/busses/i2c-pxa.c
> +++ b/drivers/i2c/busses/i2c-pxa.c
> @@ -456,7 +456,10 @@ static int i2c_pxa_wait_slave(struct pxa_i2c *i2c)
>  			return 1;
>  		}
>  
> -		msleep(1);
> +		if (in_interrupt())
> +			mdelay(1);
> +		else
> +			msleep(1);
>  	}
>  
>  	if (i2c_debug > 0)
> -- 
> 2.11.0
> 

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