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Diffstat (limited to 'arch/arc/include/asm/cmpxchg.h')
-rw-r--r--arch/arc/include/asm/cmpxchg.h26
1 files changed, 22 insertions, 4 deletions
diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h
index 03cd6894855d..44fd531f4d7b 100644
--- a/arch/arc/include/asm/cmpxchg.h
+++ b/arch/arc/include/asm/cmpxchg.h
@@ -10,6 +10,8 @@
#define __ASM_ARC_CMPXCHG_H
#include <linux/types.h>
+
+#include <asm/barrier.h>
#include <asm/smp.h>
#ifdef CONFIG_ARC_HAS_LLSC
@@ -19,16 +21,25 @@ __cmpxchg(volatile void *ptr, unsigned long expected, unsigned long new)
{
unsigned long prev;
+ /*
+ * Explicit full memory barrier needed before/after as
+ * LLOCK/SCOND thmeselves don't provide any such semantics
+ */
+ smp_mb();
+
__asm__ __volatile__(
"1: llock %0, [%1] \n"
" brne %0, %2, 2f \n"
" scond %3, [%1] \n"
" bnz 1b \n"
"2: \n"
- : "=&r"(prev)
- : "r"(ptr), "ir"(expected),
- "r"(new) /* can't be "ir". scond can't take limm for "b" */
- : "cc");
+ : "=&r"(prev) /* Early clobber, to prevent reg reuse */
+ : "r"(ptr), /* Not "m": llock only supports reg direct addr mode */
+ "ir"(expected),
+ "r"(new) /* can't be "ir". scond can't take LIMM for "b" */
+ : "cc", "memory"); /* so that gcc knows memory is being written here */
+
+ smp_mb();
return prev;
}
@@ -42,6 +53,9 @@ __cmpxchg(volatile void *ptr, unsigned long expected, unsigned long new)
int prev;
volatile unsigned long *p = ptr;
+ /*
+ * spin lock/unlock provide the needed smp_mb() before/after
+ */
atomic_ops_lock(flags);
prev = *p;
if (prev == expected)
@@ -77,12 +91,16 @@ static inline unsigned long __xchg(unsigned long val, volatile void *ptr,
switch (size) {
case 4:
+ smp_mb();
+
__asm__ __volatile__(
" ex %0, [%1] \n"
: "+r"(val)
: "r"(ptr)
: "memory");
+ smp_mb();
+
return val;
}
return __xchg_bad_pointer();