From: Takashi Iwai <tiwai@suse.de>
Subject: Re: [PATCH 23/25] ALSA/dummy: Replace tasklet with
	softirq hrtimer
Date: Thu, 31 Aug 2017 16:26:50 +0200
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References: <20170831105827.401092373@linutronix.de>
 <20170831142117.4131-1-o-takashi@sakamocchi.jp>
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To: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Cc: alsa-devel@alsa-project.org, keescook@chromium.org, peterz@infradead.org, linux-kernel@vger.kernel.org, mingo@redhat.com, john.stultz@linaro.org, tglx@linutronix.de, hch@lst.org, anna-maria@linutronix.de
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On Thu, 31 Aug 2017 16:21:17 +0200,
Takashi Sakamoto wrote:
> 
> Hi,
> 
> On Aug 31 2017 21:23, Anna-Maria Gleixner wrote:
> > From: Thomas Gleixner <tglx@linutronix.de>
> > 
> > The tasklet is used to defer the execution of snd_pcm_period_elapsed() to
> > the softirq context. Using the CLOCK_MONOTONIC_SOFT base invokes the timer
> > callback in softirq context as well which renders the tasklet useless.
> > 
> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> > Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
> > Cc: Jaroslav Kysela <perex@perex.cz>
> > Cc: Takashi Iwai <tiwai@suse.com>
> > Cc: Takashi Sakamoto <o-takashi@sakamocchi.jp>
> > Cc: alsa-devel@alsa-project.org
> > ---
> >  sound/drivers/dummy.c |   16 +++-------------
> >  1 file changed, 3 insertions(+), 13 deletions(-)
> 
> I prefer this patch as long as this driver can still receive callbacks
> from hrtimer subsystem.
> 
> Reviewed-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
> 
> Unfortunately, I have too poor machine to compile whole kernel now, thus
> didn't do any tests, sorry.
> 
> I note that ALSA pcsp driver uses a combination of hrtimer/tasklet for the
> same purpose. I think we can simplify it, too. Please refer to a patch in
> the end of this message. (But not tested yet for the above reason...)

The pcsp is a bit special.  It's really high frequent irq calls for
controlling the beep on/off, thus offloading the whole isn't good.


thanks,

Takashi