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    SubjectRe: [BUG][2.6.38] IRQ Lock Inversion / i915 fails
    Thanks a lot. That patch below does indeed
    solve the irq lock inversion problem.

    cu,
    Knut

    >
    > The trigger callback should be called always in irq-disabled context,
    > so this should be OK. But loopback_pos_update() is called in the
    > timer callback, and this can be the issue.
    >
    > Knut, how about the patch below?
    >
    >
    > thanks,
    >
    > Takashi
    >
    > ---
    > diff --git a/sound/drivers/aloop.c b/sound/drivers/aloop.c
    > index 12b44b0..a0da775 100644
    > --- a/sound/drivers/aloop.c
    > +++ b/sound/drivers/aloop.c
    > @@ -482,8 +482,9 @@ static unsigned int loopback_pos_update(struct loopback_cable *cable)
    > cable->streams[SNDRV_PCM_STREAM_CAPTURE];
    > unsigned long delta_play = 0, delta_capt = 0;
    > unsigned int running;
    > + unsigned long flags;
    >
    > - spin_lock(&cable->lock);
    > + spin_lock_irqsave(&cable->lock, flags);
    > running = cable->running ^ cable->pause;
    > if (running & (1 << SNDRV_PCM_STREAM_PLAYBACK)) {
    > delta_play = jiffies - dpcm_play->last_jiffies;
    > @@ -495,10 +496,8 @@ static unsigned int loopback_pos_update(struct loopback_cable *cable)
    > dpcm_capt->last_jiffies += delta_capt;
    > }
    >
    > - if (delta_play == 0 && delta_capt == 0) {
    > - spin_unlock(&cable->lock);
    > - return running;
    > - }
    > + if (delta_play == 0 && delta_capt == 0)
    > + goto unlock;
    >
    > if (delta_play > delta_capt) {
    > loopback_bytepos_update(dpcm_play, delta_play - delta_capt,
    > @@ -510,14 +509,14 @@ static unsigned int loopback_pos_update(struct loopback_cable *cable)
    > delta_capt = delta_play;
    > }
    >
    > - if (delta_play == 0 && delta_capt == 0) {
    > - spin_unlock(&cable->lock);
    > - return running;
    > - }
    > + if (delta_play == 0 && delta_capt == 0)
    > + goto unlock;
    > +
    > /* note delta_capt == delta_play at this moment */
    > loopback_bytepos_update(dpcm_capt, delta_capt, BYTEPOS_UPDATE_COPY);
    > loopback_bytepos_update(dpcm_play, delta_play, BYTEPOS_UPDATE_POSONLY);
    > - spin_unlock(&cable->lock);
    > + unlock:
    > + spin_unlock_irqrestore(&cable->lock, flags);
    > return running;
    > }
    >
    >



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