[PATCH] ALSA: hda/i915 - avoid hung task timeout in i915 wait

[Amadeusz Sławiński]

On 3/8/2022 3:11 PM, Kai Vehmanen wrote:
> If kernel is built with hung task detection enabled and
> CONFIG_DEFAULT_HUNG_TASK_TIMEOUT set to less than 60 seconds,
> snd_hdac_i915_init() will trigger the hung task timeout in case i915 is
> not available and taint the kernel.
> 
> Split the 60sec wait into a loop of smaller waits to avoid this.
> 
> Cc: Lucas De Marchi <lucas.demarchi at intel.com>
> Co-developed-by: Ramalingam C <ramalingam.c at intel.com>
> Signed-off-by: Ramalingam C <ramalingam.c at intel.com>
> Signed-off-by: Kai Vehmanen <kai.vehmanen at linux.intel.com>
> ---
>   sound/hda/hdac_i915.c | 10 ++++++----
>   1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/sound/hda/hdac_i915.c b/sound/hda/hdac_i915.c
> index 454474ac5716..6219de739b56 100644
> --- a/sound/hda/hdac_i915.c
> +++ b/sound/hda/hdac_i915.c
> @@ -143,7 +143,8 @@ static bool i915_gfx_present(void)
>   int snd_hdac_i915_init(struct hdac_bus *bus)
>   {
>   	struct drm_audio_component *acomp;
> -	int err;
> +	unsigned long wait = 0;

I'm not sure if it is best name for variable that is set to 0 ("false"), 
maybe `done` would be better? Especially looking at condition in the 
following for loop.

> +	int err, i;
>   
>   	if (!i915_gfx_present())
>   		return -ENODEV;
> @@ -159,9 +160,10 @@ int snd_hdac_i915_init(struct hdac_bus *bus)
>   	if (!acomp->ops) {
>   		if (!IS_ENABLED(CONFIG_MODULES) ||
>   		    !request_module("i915")) {
> -			/* 60s timeout */
> -			wait_for_completion_timeout(&acomp->master_bind_complete,
> -						    msecs_to_jiffies(60 * 1000));
> +			/* max 60s timeout */
> +			for (i = 0; !wait && i < 60; i++)
> +				wait = wait_for_completion_timeout(&acomp->master_bind_complete,
> +								   msecs_to_jiffies(1000));
>   		}
>   	}
>   	if (!acomp->ops) {
> 
> base-commit: fd7698cf0858f8c5e659b655109cd93c2f15cdd3