[x86 setup] Volatilize asm() statements

Browse source

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>

...

This commit is contained in:

H. Peter Anvin 2007-08-22 16:28:01 -07:00

parent b377fd3982

commit b015124e56

5 changed files with 30 additions and 29 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

24

arch/i386/boot/boot.h

View file

3

arch/i386/boot/cpucheck.c

View file

6

arch/i386/boot/edd.c

View file

14

arch/i386/boot/tty.c

View file

12

arch/i386/boot/video-vga.c

View file