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    SubjectRe: [PATCH 04/10] ALSA: aloop: Use always spin_lock_irqsave() for cable->lock
    On Mon, 25 Mar 2019 17:00:38 +0100,
    <twischer@de.adit-jv.com> wrote:
    >
    > From: Timo Wischer <twischer@de.adit-jv.com>
    >
    > to allow the usage of timer callbacks from interrupt context.
    > For example the sound timer.

    The trigger callback is already irq-disabled. And, open/close must
    not be irq-disabled OTOH. So these changes must be superfluous.


    thanks,

    Takashi


    >
    > Signed-off-by: Timo Wischer <twischer@de.adit-jv.com>
    > ---
    > sound/drivers/aloop.c | 33 +++++++++++++++++++--------------
    > 1 file changed, 19 insertions(+), 14 deletions(-)
    >
    > diff --git a/sound/drivers/aloop.c b/sound/drivers/aloop.c
    > index 11e8ed6..c6217c4 100644
    > --- a/sound/drivers/aloop.c
    > +++ b/sound/drivers/aloop.c
    > @@ -272,6 +272,7 @@ static int loopback_trigger(struct snd_pcm_substream *substream, int cmd)
    > struct loopback_pcm *dpcm = runtime->private_data;
    > struct loopback_cable *cable = dpcm->cable;
    > int err = 0, stream = 1 << substream->stream;
    > + unsigned long flags;
    >
    > switch (cmd) {
    > case SNDRV_PCM_TRIGGER_START:
    > @@ -281,39 +282,39 @@ static int loopback_trigger(struct snd_pcm_substream *substream, int cmd)
    > dpcm->last_jiffies = jiffies;
    > dpcm->pcm_rate_shift = 0;
    > dpcm->last_drift = 0;
    > - spin_lock(&cable->lock);
    > + spin_lock_irqsave(&cable->lock, flags);
    > cable->running |= stream;
    > cable->pause &= ~stream;
    > err = loopback_timer_start(dpcm);
    > - spin_unlock(&cable->lock);
    > + spin_unlock_irqrestore(&cable->lock, flags);
    > if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
    > loopback_active_notify(dpcm);
    > break;
    > case SNDRV_PCM_TRIGGER_STOP:
    > - spin_lock(&cable->lock);
    > + spin_lock_irqsave(&cable->lock, flags);
    > cable->running &= ~stream;
    > cable->pause &= ~stream;
    > err = loopback_timer_stop(dpcm);
    > - spin_unlock(&cable->lock);
    > + spin_unlock_irqrestore(&cable->lock, flags);
    > if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
    > loopback_active_notify(dpcm);
    > break;
    > case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
    > case SNDRV_PCM_TRIGGER_SUSPEND:
    > - spin_lock(&cable->lock);
    > + spin_lock_irqsave(&cable->lock, flags);
    > cable->pause |= stream;
    > err = loopback_timer_stop(dpcm);
    > - spin_unlock(&cable->lock);
    > + spin_unlock_irqrestore(&cable->lock, flags);
    > if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
    > loopback_active_notify(dpcm);
    > break;
    > case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
    > case SNDRV_PCM_TRIGGER_RESUME:
    > - spin_lock(&cable->lock);
    > + spin_lock_irqsave(&cable->lock, flags);
    > dpcm->last_jiffies = jiffies;
    > cable->pause &= ~stream;
    > err = loopback_timer_start(dpcm);
    > - spin_unlock(&cable->lock);
    > + spin_unlock_irqrestore(&cable->lock, flags);
    > if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
    > loopback_active_notify(dpcm);
    > break;
    > @@ -557,12 +558,13 @@ static snd_pcm_uframes_t loopback_pointer(struct snd_pcm_substream *substream)
    > {
    > struct snd_pcm_runtime *runtime = substream->runtime;
    > struct loopback_pcm *dpcm = runtime->private_data;
    > + unsigned long flags;
    > snd_pcm_uframes_t pos;
    >
    > - spin_lock(&dpcm->cable->lock);
    > + spin_lock_irqsave(&dpcm->cable->lock, flags);
    > loopback_pos_update(dpcm->cable);
    > pos = dpcm->buf_pos;
    > - spin_unlock(&dpcm->cable->lock);
    > + spin_unlock_irqrestore(&dpcm->cable->lock, flags);
    > return bytes_to_frames(runtime, pos);
    > }
    >
    > @@ -679,10 +681,12 @@ static void free_cable(struct snd_pcm_substream *substream)
    > if (!cable)
    > return;
    > if (cable->streams[!substream->stream]) {
    > + unsigned long flags;
    > +
    > /* other stream is still alive */
    > - spin_lock_irq(&cable->lock);
    > + spin_lock_irqsave(&cable->lock, flags);
    > cable->streams[substream->stream] = NULL;
    > - spin_unlock_irq(&cable->lock);
    > + spin_unlock_irqrestore(&cable->lock, flags);
    > } else {
    > /* free the cable */
    > loopback->cables[substream->number][dev] = NULL;
    > @@ -698,6 +702,7 @@ static int loopback_open(struct snd_pcm_substream *substream)
    > struct loopback_cable *cable = NULL;
    > int err = 0;
    > int dev = get_cable_index(substream);
    > + unsigned long flags;
    >
    > mutex_lock(&loopback->cable_lock);
    > dpcm = kzalloc(sizeof(*dpcm), GFP_KERNEL);
    > @@ -753,9 +758,9 @@ static int loopback_open(struct snd_pcm_substream *substream)
    > else
    > runtime->hw = cable->hw;
    >
    > - spin_lock_irq(&cable->lock);
    > + spin_lock_irqsave(&cable->lock, flags);
    > cable->streams[substream->stream] = dpcm;
    > - spin_unlock_irq(&cable->lock);
    > + spin_unlock_irqrestore(&cable->lock, flags);
    >
    > unlock:
    > if (err < 0) {
    > --
    > 2.7.4
    >
    >

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