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