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Subject[PATCH] [48/275] ALSA: hrtimer: handle delayed timer interrupts
Date
2.6.35-longterm review patch.  If anyone has any objections, please let me know.

------------------
From: Clemens Ladisch <clemens@ladisch.de>

commit b1d4f7f4bdcf9915c41ff8cfc4425c84dabb1fde upstream.

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>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Reported-and-tested-by: Arthur Marsh <arthur.marsh@internode.on.net>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
sound/core/hrtimer.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

Index: linux-2.6.35.y/sound/core/hrtimer.c
===================================================================
--- linux-2.6.35.y.orig/sound/core/hrtimer.c 2011-03-29 22:51:50.260437129 -0700
+++ linux-2.6.35.y/sound/core/hrtimer.c 2011-03-29 23:02:59.176321246 -0700
@@ -45,12 +45,13 @@
{
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;

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