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commit b1d4f7f4

 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>
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>

commit fcfdebe7

 upstream.

The timer stop callback can be called from snd_timer_interrupt(), which
is called from the hrtimer callback.  Since hrtimer_cancel() waits for
the callback completion, this eventually results in a lock-up.

This patch fixes the problem by just toggling a flag at stop callback
and call hrtimer_cancel() later.
Reported-and-tested-by: Wojtek Zabolotny <W.Zabolotny@elka.pw.edu.pl>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Use the hard-irq mode for the callback (for possible removal of
soft-irq mode in future).
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Add the license and misc comments at the beginning of the code.
Also, use ns_to_ktime() for simplification.
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Added the hrtimer backend for ALSA timer interface.
It can be used for the sequencer timer source.
Signed-off-by: Takashi Iwai <tiwai@suse.de>