Currently add_interrupt_randomness() is called at each interrupt when one
of the handlers has SA_SAMPLE_RANDOM flag, regardless whether the interrupt
is processed by that handler or not.  This results in the higher latency
and perfomance loss.

The patch fixes this behavior to avoid the unnecessary call by checking the
return value from each handler.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>