sparc32: Implement xchg and atomic_xchg using ATOMIC_HASH locks

Atomicity between xchg and cmpxchg cannot be guaranteed when xchg is
implemented with a swap and cmpxchg is implemented with locks.
Without this, e.g. mcs_spin_lock and mcs_spin_unlock are broken.

Signed-off-by: Andreas Larsson <andreas@gaisler.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/arch/sparc/include/asm/atomic_32.h b/arch/sparc/include/asm/atomic_32.h
index 765c177..0e69b7e 100644 (file)
--- a/arch/sparc/include/asm/atomic_32.h
+++ b/arch/sparc/include/asm/atomic_32.h
@@ -22,7 +22,7 @@
 
 int atomic_add_return(int, atomic_t *);
 int atomic_cmpxchg(atomic_t *, int, int);
-#define atomic_xchg(v, new) (xchg(&((v)->counter), new))
+int atomic_xchg(atomic_t *, int);
 int __atomic_add_unless(atomic_t *, int, int);
 void atomic_set(atomic_t *, int);
 

diff --git a/arch/sparc/include/asm/cmpxchg_32.h b/arch/sparc/include/asm/cmpxchg_32.h
index 32c29a1..d38b52d 100644 (file)
--- a/arch/sparc/include/asm/cmpxchg_32.h
+++ b/arch/sparc/include/asm/cmpxchg_32.h
@@ -11,22 +11,14 @@
 #ifndef __ARCH_SPARC_CMPXCHG__
 #define __ARCH_SPARC_CMPXCHG__
 
-static inline unsigned long xchg_u32(__volatile__ unsigned long *m, unsigned long val)
-{
-       __asm__ __volatile__("swap [%2], %0"
-                            : "=&r" (val)
-                            : "0" (val), "r" (m)
-                            : "memory");
-       return val;
-}
-
+unsigned long __xchg_u32(volatile u32 *m, u32 new);
 void __xchg_called_with_bad_pointer(void);
 
 static inline unsigned long __xchg(unsigned long x, __volatile__ void * ptr, int size)
 {
        switch (size) {
        case 4:
-               return xchg_u32(ptr, x);
+               return __xchg_u32(ptr, x);
        }
        __xchg_called_with_bad_pointer();
        return x;

diff --git a/arch/sparc/lib/atomic32.c b/arch/sparc/lib/atomic32.c
index a7c418a..71cd65a 100644 (file)
--- a/arch/sparc/lib/atomic32.c
+++ b/arch/sparc/lib/atomic32.c
@@ -45,6 +45,19 @@ ATOMIC_OP(add, +=)
 
 #undef ATOMIC_OP
 
+int atomic_xchg(atomic_t *v, int new)
+{
+       int ret;
+       unsigned long flags;
+
+       spin_lock_irqsave(ATOMIC_HASH(v), flags);
+       ret = v->counter;
+       v->counter = new;
+       spin_unlock_irqrestore(ATOMIC_HASH(v), flags);
+       return ret;
+}
+EXPORT_SYMBOL(atomic_xchg);
+
 int atomic_cmpxchg(atomic_t *v, int old, int new)
 {
        int ret;
@@ -137,3 +150,17 @@ unsigned long __cmpxchg_u32(volatile u32 *ptr, u32 old, u32 new)
        return (unsigned long)prev;
 }
 EXPORT_SYMBOL(__cmpxchg_u32);
+
+unsigned long __xchg_u32(volatile u32 *ptr, u32 new)
+{
+       unsigned long flags;
+       u32 prev;
+
+       spin_lock_irqsave(ATOMIC_HASH(ptr), flags);
+       prev = *ptr;
+       *ptr = new;
+       spin_unlock_irqrestore(ATOMIC_HASH(ptr), flags);
+
+       return (unsigned long)prev;
+}
+EXPORT_SYMBOL(__xchg_u32);