ALSA: hrtimer: handle delayed timer interrupts

If a timer interrupt was delayed too much, hrtimer_forward_now() will
forward the timer expiry more than once.  When this happens, the
additional number of elapsed ALSA timer ticks must be passed to
snd_timer_interrupt() to prevent the ALSA timer from falling behind.

This mostly fixes MIDI slowdown problems on highly-loaded systems with
badly behaved interrupt handlers.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Reported-and-tested-by: Arthur Marsh <arthur.marsh@internode.on.net>
Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/core/hrtimer.c b/sound/core/hrtimer.c
index 7730575..07efa29 100644 (file)
--- a/sound/core/hrtimer.c
+++ b/sound/core/hrtimer.c
@@ -45,12 +45,13 @@ static enum hrtimer_restart snd_hrtimer_callback(struct hrtimer *hrt)
 {
        struct snd_hrtimer *stime = container_of(hrt, struct snd_hrtimer, hrt);
        struct snd_timer *t = stime->timer;
+       unsigned long oruns;
 
        if (!atomic_read(&stime->running))
                return HRTIMER_NORESTART;
 
-       hrtimer_forward_now(hrt, ns_to_ktime(t->sticks * resolution));
-       snd_timer_interrupt(stime->timer, t->sticks);
+       oruns = hrtimer_forward_now(hrt, ns_to_ktime(t->sticks * resolution));
+       snd_timer_interrupt(stime->timer, t->sticks * oruns);
 
        if (!atomic_read(&stime->running))
                return HRTIMER_NORESTART;