linux-kernel - Re: [PATCH 2/3] sound: dummy, use del_timer

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Date:	Mon, 19 Jan 2015 10:52:46 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	linux-kernel@...r.kernel.org, Jaroslav Kysela <perex@...ex.cz>,
	alsa-devel@...a-project.org
Subject: Re: [PATCH 2/3] sound: dummy, use del_timer_sync

At Mon, 19 Jan 2015 10:42:55 +0100,
Jiri Slaby wrote:
> 
> Wait for the timer to really quit, not only by ensuring it is not in
> the critical section.
> 
> BTW the spin_lock in here does not disable BH, so that it could
> deadlock.

The stop function is called from the PCM trigger callback which is
irq-disabled.  So, you can't use del_timer_sync() here.


thanks,

Takashi

> 
> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
> Cc: Jaroslav Kysela <perex@...ex.cz>
> Cc: Takashi Iwai <tiwai@...e.de>
> Cc: alsa-devel@...a-project.org
> ---
>  sound/drivers/dummy.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c
> index d11baaf0f0b4..6d6bf4093583 100644
> --- a/sound/drivers/dummy.c
> +++ b/sound/drivers/dummy.c
> @@ -281,9 +281,9 @@ static int dummy_systimer_start(struct snd_pcm_substream *substream)
>  static int dummy_systimer_stop(struct snd_pcm_substream *substream)
>  {
>  	struct dummy_systimer_pcm *dpcm = substream->runtime->private_data;
> -	spin_lock(&dpcm->lock);
> -	del_timer(&dpcm->timer);
> -	spin_unlock(&dpcm->lock);
> +
> +	del_timer_sync(&dpcm->timer);
> +
>  	return 0;
>  }
>  
> -- 
> 2.2.1
> 
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