This avoids some potential stack overflows with very deep softirq callchains.
i386 does this too.

TOADD CFI annotation
Signed-off-by: NAndi Kleen <ak@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>