tree 452f3fe6b9a7d2ef692e021a18f588490bc78441
parent b377fd3982ad957c796758a90e2988401a884241
author H. Peter Anvin <hpa@zytor.com> 1187825281 -0700
committer H. Peter Anvin <hpa@zytor.com> 1187899405 -0700

[x86 setup] Volatilize asm() statements

asm() statements need to be volatile when:

a. They have side effects (other than value returned).
b. When the value returned can vary over time.
c. When they have ordering constraints that cannot be expressed to gcc.

In particular, the keyboard and timer reads were violating constraint (b),
which resulted in the keyboard/timeout poll getting
loop-invariant-removed when compiling with gcc 4.2.0.

Thanks to an anonymous bug reporter for pointing this out.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>