i386: fix setCx86/getCx86 race in macros

Because of the way the setCx86 macro is defined, a call to
setCx86(XXXX, getCx86(XXXX)) will produce the wrong output sequence.
This affects at least one place in arch/i386/kernel/setup.c :

	/* Enable MMX extensions (App note 108) */
	setCx86(CX86_CCR7, getCx86(CX86_CCR7)|1);

A correct solution consists in passing the value argument via a
temporary variable. 2.6 has a different fix using inline functions,
which produce equivalent code though.

Signed-off-by: Willy Tarreau <w@1wt.eu>

diff --git a/include/asm-i386/processor.h b/include/asm-i386/processor.h
index 81afef2..914c191 100644 (file)
--- a/include/asm-i386/processor.h
+++ b/include/asm-i386/processor.h
@@ -234,8 +234,9 @@ static inline void clear_in_cr4 (unsigned long mask)
 #define getCx86(reg) ({ outb((reg), 0x22); inb(0x23); })
 
 #define setCx86(reg, data) do { \
+       unsigned char _tmp_data = (data); \
        outb((reg), 0x22); \
-       outb((data), 0x23); \
+       outb(_tmp_data, 0x23); \
 } while (0)
 
 /*