linux-kernel - Re: [alsa-devel] [PATCH 23/25 v3] ALSA/dummy: Replace tasklet with softirq hrtimer

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Date:   Fri, 08 Sep 2017 10:28:27 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Takashi Sakamoto <o-takashi@...amocchi.jp>,
        alsa-devel@...a-project.org, keescook@...omium.org,
        linux-kernel@...r.kernel.org, peterz@...radead.org,
        mingo@...hat.com, john.stultz@...aro.org, tglx@...utronix.de,
        anna-maria@...utronix.de, hch@....de
Subject: Re: [alsa-devel] [PATCH 23/25 v3] ALSA/dummy: Replace tasklet with     softirq hrtimer

On Wed, 06 Sep 2017 06:30:03 +0200,
Takashi Sakamoto wrote:
> 
> On Sep 6 2017 01:18, Sebastian Andrzej Siewior wrote:
> > From: Thomas Gleixner <tglx@...utronix.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@...utronix.de>
> > Signed-off-by: Anna-Maria Gleixner <anna-maria@...utronix.de>
> > Cc: Jaroslav Kysela <perex@...ex.cz>
> > Cc: Takashi Iwai <tiwai@...e.com>
> > Cc: Takashi Sakamoto <o-takashi@...amocchi.jp>
> > Cc: alsa-devel@...a-project.org
> > [o-takashi: avoid stall due to a call of hrtimer_cancel() on a callback
> >              of hrtimer]
> > Signed-off-by: Takashi Sakamoto <o-takashi@...amocchi.jp>
> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> > ---
> > On 2017-09-06 01:05:43 [+0900], Takashi Sakamoto wrote:
> >> As Iwai-san mentioned, in this function, .trigger can be called in two
> >> cases; XRUN occurs and draining is done. Thus, let you change the comment as
> >> 'In cases of XRUN and draining, this calls .trigger to stop PCM substream.'.
> >> I'm sorry to trouble you.
> >>
> >> snd_pcm_period_elapsed()
> >> ->snd_pcm_update_hw_ptr0()
> >>    ->snd_pcm_update_state()
> >>      ->snd_pcm_drain_done()
> >>        ...
> >>        ->.trigger(TRIGGER_STOP)
> >>      ->xrun()
> >>        ->snd_pcm_stop()
> >>          ...
> >>          ->.trigger(TRIGGER_STOP)
> >>
> >
> > I think you asked me just to update the comment. Did I do it right?
> >
> > v2…v3: updated the comment as per Takashi Sakamoto's suggestion.
> > v1…v2: merged Takashi Sakamoto fixup of the original patch into v2.
> >
> >   sound/drivers/dummy.c | 25 +++++++++++--------------
> >   1 file changed, 11 insertions(+), 14 deletions(-)
> 
> This Looks good to me. I did quick test and confirmed that it brings
> no stalls.
> 
> Tested-by: Takashi Sakamoto <o-takashi@...amocchi.jp>

I suppose you'd apply all together in some tree like tip or whatever?
In anyway, feel free to take my ack for this patch:
  Reviewed-by: Takashi Iwai <tiwai@...e.de>


Thanks!

Takashi