[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/arch/i386/Kconfig b/arch/i386/Kconfig
index 2e3e8dbcb79f30f369c673661652cbd0442801c2..35d3cff3005702f0dc939060720240e769edf207 100644 (file)
--- a/arch/i386/Kconfig
+++ b/arch/i386/Kconfig
@@ -424,6 +424,11 @@ config X86_POPAD_OK
        depends on !M386
        default y
 
+config X86_CMPXCHG64
+       bool
+       depends on !M386 && !M486
+       default y
+
 config X86_ALIGNMENT_16
        bool
        depends on MWINCHIP3D || MWINCHIP2 || MWINCHIPC6 || MCYRIXIII || X86_ELAN || MK6 || M586MMX || M586TSC || M586 || M486 || MVIAC3_2 || MGEODEGX1

diff --git a/include/asm-i386/system.h b/include/asm-i386/system.h
index acd5c26b69ba68f9a2964b59cdf01b86daab9fda..97d52ac49e46626eac3018e388695147525c476b 100644 (file)
--- a/include/asm-i386/system.h
+++ b/include/asm-i386/system.h
@@ -167,6 +167,8 @@ struct __xchg_dummy { unsigned long a[100]; };
 #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 @@ static inline void __set_64bit_var (unsigned long long *ptr,
  __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 @@ static inline unsigned long __xchg(unsigned long x, volatile void * ptr, int siz
 
 #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 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
        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 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
 #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 {