linux-kernel - Re: [PATCH] OSS: mpu401, fix deadlock

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Date:	Mon, 29 Jun 2009 18:09:49 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Jiri Slaby <jirislaby@...il.com>
Cc:	perex@...ex.cz, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] OSS: mpu401, fix deadlock

At Mon, 29 Jun 2009 18:03:34 +0200,
Jiri Slaby wrote:
> 
> If somebody cares about oss at all.

... or want to save somebody else's time to find out the same bug :)

> --
> mpu401_chk_version is called with a spin lock already held. Don't take it
> again.
> 
> Signed-off-by: Jiri Slaby <jirislaby@...il.com>

Applied now.  Thanks.


Takashi

> ---
>  sound/oss/mpu401.c |   16 +++-------------
>  1 files changed, 3 insertions(+), 13 deletions(-)
> 
> diff --git a/sound/oss/mpu401.c b/sound/oss/mpu401.c
> index 6c0a770..1b2316f 100644
> --- a/sound/oss/mpu401.c
> +++ b/sound/oss/mpu401.c
> @@ -926,31 +926,21 @@ static struct midi_operations mpu401_midi_operations[MAX_MIDI_DEV];
>  static void mpu401_chk_version(int n, struct mpu_config *devc)
>  {
>  	int tmp;
> -	unsigned long flags;
>  
>  	devc->version = devc->revision = 0;
>  
> -	spin_lock_irqsave(&devc->lock,flags);
> -	if ((tmp = mpu_cmd(n, 0xAC, 0)) < 0)
> -	{
> -		spin_unlock_irqrestore(&devc->lock,flags);
> +	tmp = mpu_cmd(n, 0xAC, 0);
> +	if (tmp < 0)
>  		return;
> -	}
>  	if ((tmp & 0xf0) > 0x20)	/* Why it's larger than 2.x ??? */
> -	{
> -		spin_unlock_irqrestore(&devc->lock,flags);
>  		return;
> -	}
>  	devc->version = tmp;
>  
> -	if ((tmp = mpu_cmd(n, 0xAD, 0)) < 0)
> -	{
> +	if ((tmp = mpu_cmd(n, 0xAD, 0)) < 0) {
>  		devc->version = 0;
> -		spin_unlock_irqrestore(&devc->lock,flags);
>  		return;
>  	}
>  	devc->revision = tmp;
> -	spin_unlock_irqrestore(&devc->lock,flags);
>  }
>  
>  int attach_mpu401(struct address_info *hw_config, struct module *owner)
> -- 
> 1.6.3.2
> 
--
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