linux-kernel - Re: [PATCH 6/6] sound/isa: convert nested spin_lock_irqsave to spin

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Date:	Sun, 19 Jul 2009 14:03:26 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Julia Lawall <julia@...u.dk>
Cc:	perex@...ex.cz, alsa-devel@...a-project.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 6/6] sound/isa: convert nested spin_lock_irqsave to spin_lock

At Sat, 18 Jul 2009 17:26:14 +0200 (CEST),
Julia Lawall wrote:
> 
> From: Julia Lawall <julia@...u.dk>
> 
> If spin_lock_irqsave is called twice in a row with the same second
> argument, the interrupt state at the point of the second call overwrites
> the value saved by the first call.  Indeed, the second call does not need
> to save the interrupt state, so it is changed to a simple spin_lock.
> 
> The semantic match that finds this problem is as follows:
> (http://www.emn.fr/x-info/coccinelle/)
> 
> // <smpl>
> @@
> expression lock1,lock2;
> expression flags;
> @@
> 
> *spin_lock_irqsave(lock1,flags)
> ... when != flags
> *spin_lock_irqsave(lock2,flags)
> // </smpl>
> 
> Signed-off-by: Julia Lawall <julia@...u.dk>

Applied now.  Thanks.


Takashi

> 
> ---
>  sound/isa/gus/gus_pcm.c             |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/sound/isa/gus/gus_pcm.c b/sound/isa/gus/gus_pcm.c
> index edb11ee..2dcf45b 100644
> --- a/sound/isa/gus/gus_pcm.c
> +++ b/sound/isa/gus/gus_pcm.c
> @@ -795,13 +795,13 @@ static int snd_gf1_pcm_volume_put(struct snd_kcontrol *kcontrol, struct snd_ctl_
>  		if (!(pcmp->flags & SNDRV_GF1_PCM_PFLG_ACTIVE))
>  			continue;
>  		/* load real volume - better precision */
> -		spin_lock_irqsave(&gus->reg_lock, flags);
> +		spin_lock(&gus->reg_lock);
>  		snd_gf1_select_voice(gus, pvoice->number);
>  		snd_gf1_ctrl_stop(gus, SNDRV_GF1_VB_VOLUME_CONTROL);
>  		vol = pvoice == pcmp->pvoices[0] ? gus->gf1.pcm_volume_level_left : gus->gf1.pcm_volume_level_right;
>  		snd_gf1_write16(gus, SNDRV_GF1_VW_VOLUME, vol);
>  		pcmp->final_volume = 1;
> -		spin_unlock_irqrestore(&gus->reg_lock, flags);
> +		spin_unlock(&gus->reg_lock);
>  	}
>  	spin_unlock_irqrestore(&gus->voice_alloc, flags);
>  	return change;
> 
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