Re: [PATCH v2 04/13] ASoC: SDCA: Correct FDL locking with scoped_guard

[Charles Keepax <ckeepax@opensource.cirrus.com>]

On Mon, Nov 03, 2025 at 03:07:59PM +0000, Charles Keepax wrote:
> The current locking in sdca_fdl_process() locks over
> sdca_ump_cancel_timeout() and the timeout work function takes the same
> lock, this can lead to a deadlock if the work runs as part of the
> cancel. To fix this use scoped_guard and move the cancel timeout to be
> outside the lock.
> 
> Fixes: e92e25f77748 ("ASoC: SDCA: Add UMP timeout handling for FDL")
> Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
> ---
> 
> New since v1.
> 
>  sound/soc/sdca/sdca_fdl.c | 90 ++++++++++++++++++++-------------------
>  1 file changed, 46 insertions(+), 44 deletions(-)
> 
> diff --git a/sound/soc/sdca/sdca_fdl.c b/sound/soc/sdca/sdca_fdl.c
> index cb79dc3131b82..fe0ef2df4d9eb 100644
> --- a/sound/soc/sdca/sdca_fdl.c
> +++ b/sound/soc/sdca/sdca_fdl.c
> @@ -402,8 +402,6 @@ int sdca_fdl_process(struct sdca_interrupt *interrupt)
>  	unsigned int reg, status;
>  	int response, ret;
>  
> -	guard(mutex)(&fdl_state->lock);
> -
>  	ret = sdca_ump_get_owner_host(dev, interrupt->function_regmap,
>  				      interrupt->function, interrupt->entity,
>  				      interrupt->control);
> @@ -412,56 +410,60 @@ int sdca_fdl_process(struct sdca_interrupt *interrupt)
>  
>  	sdca_ump_cancel_timeout(&fdl_state->timeout);
>  
> -	reg = SDW_SDCA_CTL(interrupt->function->desc->adr, interrupt->entity->id,
> -			   SDCA_CTL_XU_FDL_STATUS, 0);
> -	ret = regmap_read(interrupt->function_regmap, reg, &status);
> -	if (ret < 0) {
> -		dev_err(dev, "failed to read FDL status: %d\n", ret);
> -		return ret;
> -	}
> +	scoped_guard(mutex, &fdl_state->lock) {

My esteemed colleague Maciej has pointed out (off list) we can
just move the guard down rather than switching to scoped_guard
since the whole reset of the function is covered. This makes the
patch much nicer so I will respin for that soon.

Thanks,
Charles