linux-kernel - Re: [PATCH] ali5451: fix timeout handling in snd_ali_{codecs,timer}

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Message-ID: <s5hy6paihx7.wl%tiwai@suse.de>
Date:	Sun, 23 Aug 2009 19:00:52 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
Cc:	Jack Byer <ojbyer@....net>, alsa-devel@...a-project.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ali5451: fix timeout handling in snd_ali_{codecs,timer}_ready()

At Sun, 23 Aug 2009 15:27:25 +0200,
Bartlomiej Zolnierkiewicz wrote:
> 
> On Thursday 20 August 2009 08:33:21 Takashi Iwai wrote:
> > At Wed, 19 Aug 2009 22:09:50 +0200,
> > Bartlomiej Zolnierkiewicz wrote:
> > > 
> > > From: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
> > > Subject: [PATCH] ali5451: fix timeout handling in snd_ali_{codecs,timer}_ready()
> > > 
> > > Modify loops in such way that the register value is checked also after
> > > the timeout condition, just in case the heavy interrupt load etc. caused
> > > the thread to sleep for the time period exceeding the timeout value.
> > > 
> > > While at it remove an extra ALI_STIMER read from snd_ali_stimer_ready().
> > > 
> > > Reported-by: Jack Byer <ojbyer@....net>
> > > Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
> > > ---
> > >  sound/pci/ali5451/ali5451.c |   11 ++++++++---
> > >  1 file changed, 8 insertions(+), 3 deletions(-)
> > > 
> > > Index: b/sound/pci/ali5451/ali5451.c
> > > ===================================================================
> > > --- a/sound/pci/ali5451/ali5451.c
> > > +++ b/sound/pci/ali5451/ali5451.c
> > > @@ -314,8 +314,11 @@ static int snd_ali_codec_ready(struct sn
> > >  		res = snd_ali_5451_peek(codec,port);
> > >  		if (!(res & 0x8000))
> > >  			return 0;
> > > +		if (!time_after_eq(end_time, jiffies))
> > > +			break;
> > >  		schedule_timeout_uninterruptible(1);
> > > -	} while (time_after_eq(end_time, jiffies));
> > > +	} while (1);
> > 
> > Using for (;;) is more generic.  I see your patch keeps the changes
> > minimal, but I'm afraid that the result, do {} while(1), can be
> > misleading.
> > 
> > Could you replace with for (;;) ?
> 
> Sure, though I don't see a much value added from this operation..

Heh, it would save one commit I'd do unnecessarily ;)

> From: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
> Subject: [PATCH v2] ali5451: fix timeout handling in snd_ali_{codecs,timer}_ready()
> 
> Modify loops in such way that the register value is checked also after
> the timeout condition, just in case the heavy interrupt load etc. caused
> the thread to sleep for the time period exceeding the timeout value.
> 
> While at it remove an extra ALI_STIMER read from snd_ali_stimer_ready().
> 
> Reported-by: Jack Byer <ojbyer@....net>
> Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>

Thanks, applied now.


Takashi

> ---
>  sound/pci/ali5451/ali5451.c |   18 ++++++++++++------
>  1 file changed, 12 insertions(+), 6 deletions(-)
> 
> Index: b/sound/pci/ali5451/ali5451.c
> ===================================================================
> --- a/sound/pci/ali5451/ali5451.c
> +++ b/sound/pci/ali5451/ali5451.c
> @@ -310,12 +310,16 @@ static int snd_ali_codec_ready(struct sn
>  	unsigned int res;
>  	
>  	end_time = jiffies + msecs_to_jiffies(250);
> -	do {
> +
> +	for (;;) {
>  		res = snd_ali_5451_peek(codec,port);
>  		if (!(res & 0x8000))
>  			return 0;
> +		if (!time_after_eq(end_time, jiffies))
> +			break;
>  		schedule_timeout_uninterruptible(1);
> -	} while (time_after_eq(end_time, jiffies));
> +	}
> +
>  	snd_ali_5451_poke(codec, port, res & ~0x8000);
>  	snd_printdd("ali_codec_ready: codec is not ready.\n ");
>  	return -EIO;
> @@ -327,15 +331,17 @@ static int snd_ali_stimer_ready(struct s
>  	unsigned long dwChk1,dwChk2;
>  	
>  	dwChk1 = snd_ali_5451_peek(codec, ALI_STIMER);
> -	dwChk2 = snd_ali_5451_peek(codec, ALI_STIMER);
> -
>  	end_time = jiffies + msecs_to_jiffies(250);
> -	do {
> +
> +	for (;;) {
>  		dwChk2 = snd_ali_5451_peek(codec, ALI_STIMER);
>  		if (dwChk2 != dwChk1)
>  			return 0;
> +		if (!time_after_eq(end_time, jiffies))
> +			break;
>  		schedule_timeout_uninterruptible(1);
> -	} while (time_after_eq(end_time, jiffies));
> +	}
> +
>  	snd_printk(KERN_ERR "ali_stimer_read: stimer is not ready.\n");
>  	return -EIO;
>  }
> 
> 
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