From: Zwane Mwaikambo <zwane@linuxpower.ca>

Following up on Keith's code, I adapted the i386 code to allow enabling
interrupts during contested locks depending on previous interrupt
enable status. Obviously there will be a text increase (only for non
CONFIG_SPINLINE case), although it doesn't seem so bad, there will be an
increased exit latency when we attempt a lock acquisition after spinning
due to the extra instructions. How much this will affect performance I'm
not sure yet as I haven't had time to micro bench.

   text    data     bss     dec     hex filename
2628024  921731       0 3549755  362a3b vmlinux-after
2621369  921731       0 3543100  36103c vmlinux-before
2618313  919222       0 3537535  35fa7f vmlinux-spinline

The code has been stress tested on a 16x NUMAQ (courtesy OSDL).
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>