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Diffstat (limited to 'arch/alpha/include/asm/xchg.h')
-rw-r--r--arch/alpha/include/asm/xchg.h38
1 files changed, 26 insertions, 12 deletions
diff --git a/arch/alpha/include/asm/xchg.h b/arch/alpha/include/asm/xchg.h
index 68dfb3cb7145..e2b59fac5257 100644
--- a/arch/alpha/include/asm/xchg.h
+++ b/arch/alpha/include/asm/xchg.h
@@ -12,6 +12,10 @@
* Atomic exchange.
* Since it can be used to implement critical sections
* it must clobber "memory" (also for interrupts in UP).
+ *
+ * The leading and the trailing memory barriers guarantee that these
+ * operations are fully ordered.
+ *
*/
static inline unsigned long
@@ -19,6 +23,7 @@ ____xchg(_u8, volatile char *m, unsigned long val)
{
unsigned long ret, tmp, addr64;
+ smp_mb();
__asm__ __volatile__(
" andnot %4,7,%3\n"
" insbl %1,%4,%1\n"
@@ -28,12 +33,12 @@ ____xchg(_u8, volatile char *m, unsigned long val)
" or %1,%2,%2\n"
" stq_c %2,0(%3)\n"
" beq %2,2f\n"
- __ASM__MB
".subsection 2\n"
"2: br 1b\n"
".previous"
: "=&r" (ret), "=&r" (val), "=&r" (tmp), "=&r" (addr64)
: "r" ((long)m), "1" (val) : "memory");
+ smp_mb();
return ret;
}
@@ -43,6 +48,7 @@ ____xchg(_u16, volatile short *m, unsigned long val)
{
unsigned long ret, tmp, addr64;
+ smp_mb();
__asm__ __volatile__(
" andnot %4,7,%3\n"
" inswl %1,%4,%1\n"
@@ -52,12 +58,12 @@ ____xchg(_u16, volatile short *m, unsigned long val)
" or %1,%2,%2\n"
" stq_c %2,0(%3)\n"
" beq %2,2f\n"
- __ASM__MB
".subsection 2\n"
"2: br 1b\n"
".previous"
: "=&r" (ret), "=&r" (val), "=&r" (tmp), "=&r" (addr64)
: "r" ((long)m), "1" (val) : "memory");
+ smp_mb();
return ret;
}
@@ -67,17 +73,18 @@ ____xchg(_u32, volatile int *m, unsigned long val)
{
unsigned long dummy;
+ smp_mb();
__asm__ __volatile__(
"1: ldl_l %0,%4\n"
" bis $31,%3,%1\n"
" stl_c %1,%2\n"
" beq %1,2f\n"
- __ASM__MB
".subsection 2\n"
"2: br 1b\n"
".previous"
: "=&r" (val), "=&r" (dummy), "=m" (*m)
: "rI" (val), "m" (*m) : "memory");
+ smp_mb();
return val;
}
@@ -87,17 +94,18 @@ ____xchg(_u64, volatile long *m, unsigned long val)
{
unsigned long dummy;
+ smp_mb();
__asm__ __volatile__(
"1: ldq_l %0,%4\n"
" bis $31,%3,%1\n"
" stq_c %1,%2\n"
" beq %1,2f\n"
- __ASM__MB
".subsection 2\n"
"2: br 1b\n"
".previous"
: "=&r" (val), "=&r" (dummy), "=m" (*m)
: "rI" (val), "m" (*m) : "memory");
+ smp_mb();
return val;
}
@@ -128,10 +136,12 @@ ____xchg(, volatile void *ptr, unsigned long x, int size)
* store NEW in MEM. Return the initial value in MEM. Success is
* indicated by comparing RETURN with OLD.
*
- * The memory barrier should be placed in SMP only when we actually
- * make the change. If we don't change anything (so if the returned
- * prev is equal to old) then we aren't acquiring anything new and
- * we don't need any memory barrier as far I can tell.
+ * The leading and the trailing memory barriers guarantee that these
+ * operations are fully ordered.
+ *
+ * The trailing memory barrier is placed in SMP unconditionally, in
+ * order to guarantee that dependency ordering is preserved when a
+ * dependency is headed by an unsuccessful operation.
*/
static inline unsigned long
@@ -139,6 +149,7 @@ ____cmpxchg(_u8, volatile char *m, unsigned char old, unsigned char new)
{
unsigned long prev, tmp, cmp, addr64;
+ smp_mb();
__asm__ __volatile__(
" andnot %5,7,%4\n"
" insbl %1,%5,%1\n"
@@ -150,13 +161,13 @@ ____cmpxchg(_u8, volatile char *m, unsigned char old, unsigned char new)
" or %1,%2,%2\n"
" stq_c %2,0(%4)\n"
" beq %2,3f\n"
- __ASM__MB
"2:\n"
".subsection 2\n"
"3: br 1b\n"
".previous"
: "=&r" (prev), "=&r" (new), "=&r" (tmp), "=&r" (cmp), "=&r" (addr64)
: "r" ((long)m), "Ir" (old), "1" (new) : "memory");
+ smp_mb();
return prev;
}
@@ -166,6 +177,7 @@ ____cmpxchg(_u16, volatile short *m, unsigned short old, unsigned short new)
{
unsigned long prev, tmp, cmp, addr64;
+ smp_mb();
__asm__ __volatile__(
" andnot %5,7,%4\n"
" inswl %1,%5,%1\n"
@@ -177,13 +189,13 @@ ____cmpxchg(_u16, volatile short *m, unsigned short old, unsigned short new)
" or %1,%2,%2\n"
" stq_c %2,0(%4)\n"
" beq %2,3f\n"
- __ASM__MB
"2:\n"
".subsection 2\n"
"3: br 1b\n"
".previous"
: "=&r" (prev), "=&r" (new), "=&r" (tmp), "=&r" (cmp), "=&r" (addr64)
: "r" ((long)m), "Ir" (old), "1" (new) : "memory");
+ smp_mb();
return prev;
}
@@ -193,6 +205,7 @@ ____cmpxchg(_u32, volatile int *m, int old, int new)
{
unsigned long prev, cmp;
+ smp_mb();
__asm__ __volatile__(
"1: ldl_l %0,%5\n"
" cmpeq %0,%3,%1\n"
@@ -200,13 +213,13 @@ ____cmpxchg(_u32, volatile int *m, int old, int new)
" mov %4,%1\n"
" stl_c %1,%2\n"
" beq %1,3f\n"
- __ASM__MB
"2:\n"
".subsection 2\n"
"3: br 1b\n"
".previous"
: "=&r"(prev), "=&r"(cmp), "=m"(*m)
: "r"((long) old), "r"(new), "m"(*m) : "memory");
+ smp_mb();
return prev;
}
@@ -216,6 +229,7 @@ ____cmpxchg(_u64, volatile long *m, unsigned long old, unsigned long new)
{
unsigned long prev, cmp;
+ smp_mb();
__asm__ __volatile__(
"1: ldq_l %0,%5\n"
" cmpeq %0,%3,%1\n"
@@ -223,13 +237,13 @@ ____cmpxchg(_u64, volatile long *m, unsigned long old, unsigned long new)
" mov %4,%1\n"
" stq_c %1,%2\n"
" beq %1,3f\n"
- __ASM__MB
"2:\n"
".subsection 2\n"
"3: br 1b\n"
".previous"
: "=&r"(prev), "=&r"(cmp), "=m"(*m)
: "r"((long) old), "r"(new), "m"(*m) : "memory");
+ smp_mb();
return prev;
}