[PATCH] x86: cmpxchg improvements
This adjusts i386's cmpxchg patterns so that
- for word and long cmpxchg-es the compiler can utilize all possible
registers
- cmpxchg8b gets disabled when the minimum specified hardware architectur
doesn't support it (like was already happening for the byte, word, and
long ones).
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/asm-i386/system.h b/include/asm-i386/system.h
index acd5c26..97d52ac 100644
--- a/include/asm-i386/system.h
+++ b/include/asm-i386/system.h
@@ -167,6 +167,8 @@
#define __xg(x) ((struct __xchg_dummy *)(x))
+#ifdef CONFIG_X86_CMPXCHG64
+
/*
* The semantics of XCHGCMP8B are a bit strange, this is why
* there is a loop and the loading of %%eax and %%edx has to
@@ -221,6 +223,8 @@
__set_64bit(ptr, (unsigned int)(value), (unsigned int)((value)>>32ULL) ) : \
__set_64bit(ptr, ll_low(value), ll_high(value)) )
+#endif
+
/*
* Note: no "lock" prefix even on SMP: xchg always implies lock anyway
* Note 2: xchg has side effect, so that attribute volatile is necessary,
@@ -259,7 +263,6 @@
#ifdef CONFIG_X86_CMPXCHG
#define __HAVE_ARCH_CMPXCHG 1
-#endif
static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
unsigned long new, int size)
@@ -275,13 +278,13 @@
case 2:
__asm__ __volatile__(LOCK_PREFIX "cmpxchgw %w1,%2"
: "=a"(prev)
- : "q"(new), "m"(*__xg(ptr)), "0"(old)
+ : "r"(new), "m"(*__xg(ptr)), "0"(old)
: "memory");
return prev;
case 4:
__asm__ __volatile__(LOCK_PREFIX "cmpxchgl %1,%2"
: "=a"(prev)
- : "q"(new), "m"(*__xg(ptr)), "0"(old)
+ : "r"(new), "m"(*__xg(ptr)), "0"(old)
: "memory");
return prev;
}
@@ -291,6 +294,30 @@
#define cmpxchg(ptr,o,n)\
((__typeof__(*(ptr)))__cmpxchg((ptr),(unsigned long)(o),\
(unsigned long)(n),sizeof(*(ptr))))
+
+#endif
+
+#ifdef CONFIG_X86_CMPXCHG64
+
+static inline unsigned long long __cmpxchg64(volatile void *ptr, unsigned long long old,
+ unsigned long long new)
+{
+ unsigned long long prev;
+ __asm__ __volatile__(LOCK_PREFIX "cmpxchg8b %3"
+ : "=A"(prev)
+ : "b"((unsigned long)new),
+ "c"((unsigned long)(new >> 32)),
+ "m"(*__xg(ptr)),
+ "0"(old)
+ : "memory");
+ return prev;
+}
+
+#define cmpxchg64(ptr,o,n)\
+ ((__typeof__(*(ptr)))__cmpxchg64((ptr),(unsigned long long)(o),\
+ (unsigned long long)(n)))
+
+#endif
#ifdef __KERNEL__
struct alt_instr {