linux-kernel - Re: [PATCH v4] ALSA: usb-audio: qcom: Adjust mutex unlock order

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Message-ID: <87ms8wo991.wl-tiwai@suse.de>
Date: Tue, 22 Jul 2025 11:38:50 +0200
From: Takashi Iwai <tiwai@...e.de>
To: Erick Karanja <karanja99erick@...il.com>
Cc: perex@...ex.cz,
	tiwai@...e.com,
	linux-sound@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] ALSA: usb-audio: qcom: Adjust mutex unlock order

On Mon, 21 Jul 2025 13:45:53 +0200,
Erick Karanja wrote:
> 
> The mutexes qdev_mutex and chip->mutex are acquired in that order
> throughout the driver. To preserve proper lock hierarchy and avoid
> potential deadlocks, they must be released in the reverse
> order of acquisition.
> 
> This change reorders the unlock sequence to first release chip->mutex
> followed by qdev_mutex, ensuring consistency with the locking pattern.
> 
> Fixes: 326bbc348298a ("ALSA: usb-audio: qcom: Introduce QC USB
>                       SND offloading support")

This has to be a single line without folding.

> changes since v3:
>  - Add the correct fixes tag.
> 
> Signed-off-by: Erick Karanja <karanja99erick@...il.com>
> ---
>  sound/usb/qcom/qc_audio_offload.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/sound/usb/qcom/qc_audio_offload.c b/sound/usb/qcom/qc_audio_offload.c
> index 3543b5a53592..711f5612a83a 100644
> --- a/sound/usb/qcom/qc_audio_offload.c
> +++ b/sound/usb/qcom/qc_audio_offload.c
> @@ -825,8 +825,8 @@ static int uaudio_sideband_notifier(struct usb_interface *intf,
>  		}
>  	}
>  
> -	mutex_unlock(&qdev_mutex);
>  	mutex_unlock(&chip->mutex);
> +	mutex_unlock(&qdev_mutex);
>  
>  	return 0;
>  }
> @@ -1865,8 +1865,8 @@ static void qc_usb_audio_offload_disconnect(struct snd_usb_audio *chip)
>  
>  	/* Device has already been cleaned up, or never populated */
>  	if (!dev->chip) {
> -		mutex_unlock(&qdev_mutex);
>  		mutex_unlock(&chip->mutex);
> +		mutex_unlock(&qdev_mutex);
>  		return;
>  	}
>  
> @@ -1921,8 +1921,8 @@ static void qc_usb_audio_offload_suspend(struct usb_interface *intf,
>  
>  	uaudio_send_disconnect_ind(chip);
>  
> +        mutex_unlock(&chip->mutex);
>  	mutex_unlock(&qdev_mutex);
> -	mutex_unlock(&chip->mutex);

The above used spaces instead of tabs, and I corrected in my side.
Such a failure could be spotted out by running scripts/checkpatch.pl.
At the next time, please run and test it before submissions.

In anyway, I applied the patch now.


thanks,

Takashi