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Subject[PATCH 1/5] x86/percpu: Differentiate this_cpu_{}() and __this_cpu_{}()
Nadav Amit reported that commit:

b59167ac7baf ("x86/percpu: Fix this_cpu_read()")

added a bunch of constraints to all sorts of code; and while some of
that was correct and desired, some of that seems superfluous.

The thing is, the this_cpu_*() operations are defined IRQ-safe, this
means the values are subject to change from IRQs, and thus must be
reloaded.

Also (the generic form):

local_irq_save()
__this_cpu_read()
local_irq_restore()

would not allow the re-use of previous values; if by nothing else,
then the barrier()s implied by local_irq_*().

Which raises the point that percpu_from_op() and the other also need
that volatile.

OTOH __this_cpu_*() operations are not IRQ-safe and assume external
preempt/IRQ disabling and could thus be allowed more room for
optimization.

Reported-by: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/include/asm/percpu.h | 224 +++++++++++++++++++++---------------------
1 file changed, 112 insertions(+), 112 deletions(-)

--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -87,7 +87,7 @@
* don't give an lvalue though). */
extern void __bad_percpu_size(void);

-#define percpu_to_op(op, var, val) \
+#define percpu_to_op(qual, op, var, val) \
do { \
typedef typeof(var) pto_T__; \
if (0) { \
@@ -97,22 +97,22 @@ do { \
} \
switch (sizeof(var)) { \
case 1: \
- asm(op "b %1,"__percpu_arg(0) \
+ asm qual (op "b %1,"__percpu_arg(0) \
: "+m" (var) \
: "qi" ((pto_T__)(val))); \
break; \
case 2: \
- asm(op "w %1,"__percpu_arg(0) \
+ asm qual (op "w %1,"__percpu_arg(0) \
: "+m" (var) \
: "ri" ((pto_T__)(val))); \
break; \
case 4: \
- asm(op "l %1,"__percpu_arg(0) \
+ asm qual (op "l %1,"__percpu_arg(0) \
: "+m" (var) \
: "ri" ((pto_T__)(val))); \
break; \
case 8: \
- asm(op "q %1,"__percpu_arg(0) \
+ asm qual (op "q %1,"__percpu_arg(0) \
: "+m" (var) \
: "re" ((pto_T__)(val))); \
break; \
@@ -124,7 +124,7 @@ do { \
* Generate a percpu add to memory instruction and optimize code
* if one is added or subtracted.
*/
-#define percpu_add_op(var, val) \
+#define percpu_add_op(qual, var, val) \
do { \
typedef typeof(var) pao_T__; \
const int pao_ID__ = (__builtin_constant_p(val) && \
@@ -138,41 +138,41 @@ do { \
switch (sizeof(var)) { \
case 1: \
if (pao_ID__ == 1) \
- asm("incb "__percpu_arg(0) : "+m" (var)); \
+ asm qual ("incb "__percpu_arg(0) : "+m" (var)); \
else if (pao_ID__ == -1) \
- asm("decb "__percpu_arg(0) : "+m" (var)); \
+ asm qual ("decb "__percpu_arg(0) : "+m" (var)); \
else \
- asm("addb %1, "__percpu_arg(0) \
+ asm qual ("addb %1, "__percpu_arg(0) \
: "+m" (var) \
: "qi" ((pao_T__)(val))); \
break; \
case 2: \
if (pao_ID__ == 1) \
- asm("incw "__percpu_arg(0) : "+m" (var)); \
+ asm qual ("incw "__percpu_arg(0) : "+m" (var)); \
else if (pao_ID__ == -1) \
- asm("decw "__percpu_arg(0) : "+m" (var)); \
+ asm qual ("decw "__percpu_arg(0) : "+m" (var)); \
else \
- asm("addw %1, "__percpu_arg(0) \
+ asm qual ("addw %1, "__percpu_arg(0) \
: "+m" (var) \
: "ri" ((pao_T__)(val))); \
break; \
case 4: \
if (pao_ID__ == 1) \
- asm("incl "__percpu_arg(0) : "+m" (var)); \
+ asm qual ("incl "__percpu_arg(0) : "+m" (var)); \
else if (pao_ID__ == -1) \
- asm("decl "__percpu_arg(0) : "+m" (var)); \
+ asm qual ("decl "__percpu_arg(0) : "+m" (var)); \
else \
- asm("addl %1, "__percpu_arg(0) \
+ asm qual ("addl %1, "__percpu_arg(0) \
: "+m" (var) \
: "ri" ((pao_T__)(val))); \
break; \
case 8: \
if (pao_ID__ == 1) \
- asm("incq "__percpu_arg(0) : "+m" (var)); \
+ asm qual ("incq "__percpu_arg(0) : "+m" (var)); \
else if (pao_ID__ == -1) \
- asm("decq "__percpu_arg(0) : "+m" (var)); \
+ asm qual ("decq "__percpu_arg(0) : "+m" (var)); \
else \
- asm("addq %1, "__percpu_arg(0) \
+ asm qual ("addq %1, "__percpu_arg(0) \
: "+m" (var) \
: "re" ((pao_T__)(val))); \
break; \
@@ -180,27 +180,27 @@ do { \
} \
} while (0)

-#define percpu_from_op(op, var) \
+#define percpu_from_op(qual, op, var) \
({ \
typeof(var) pfo_ret__; \
switch (sizeof(var)) { \
case 1: \
- asm volatile(op "b "__percpu_arg(1)",%0"\
+ asm qual (op "b "__percpu_arg(1)",%0" \
: "=q" (pfo_ret__) \
: "m" (var)); \
break; \
case 2: \
- asm volatile(op "w "__percpu_arg(1)",%0"\
+ asm qual (op "w "__percpu_arg(1)",%0" \
: "=r" (pfo_ret__) \
: "m" (var)); \
break; \
case 4: \
- asm volatile(op "l "__percpu_arg(1)",%0"\
+ asm qual (op "l "__percpu_arg(1)",%0" \
: "=r" (pfo_ret__) \
: "m" (var)); \
break; \
case 8: \
- asm volatile(op "q "__percpu_arg(1)",%0"\
+ asm qual (op "q "__percpu_arg(1)",%0" \
: "=r" (pfo_ret__) \
: "m" (var)); \
break; \
@@ -238,23 +238,23 @@ do { \
pfo_ret__; \
})

-#define percpu_unary_op(op, var) \
+#define percpu_unary_op(qual, op, var) \
({ \
switch (sizeof(var)) { \
case 1: \
- asm(op "b "__percpu_arg(0) \
+ asm qual (op "b "__percpu_arg(0) \
: "+m" (var)); \
break; \
case 2: \
- asm(op "w "__percpu_arg(0) \
+ asm qual (op "w "__percpu_arg(0) \
: "+m" (var)); \
break; \
case 4: \
- asm(op "l "__percpu_arg(0) \
+ asm qual (op "l "__percpu_arg(0) \
: "+m" (var)); \
break; \
case 8: \
- asm(op "q "__percpu_arg(0) \
+ asm qual (op "q "__percpu_arg(0) \
: "+m" (var)); \
break; \
default: __bad_percpu_size(); \
@@ -264,27 +264,27 @@ do { \
/*
* Add return operation
*/
-#define percpu_add_return_op(var, val) \
+#define percpu_add_return_op(qual, var, val) \
({ \
typeof(var) paro_ret__ = val; \
switch (sizeof(var)) { \
case 1: \
- asm("xaddb %0, "__percpu_arg(1) \
+ asm qual ("xaddb %0, "__percpu_arg(1) \
: "+q" (paro_ret__), "+m" (var) \
: : "memory"); \
break; \
case 2: \
- asm("xaddw %0, "__percpu_arg(1) \
+ asm qual ("xaddw %0, "__percpu_arg(1) \
: "+r" (paro_ret__), "+m" (var) \
: : "memory"); \
break; \
case 4: \
- asm("xaddl %0, "__percpu_arg(1) \
+ asm qual ("xaddl %0, "__percpu_arg(1) \
: "+r" (paro_ret__), "+m" (var) \
: : "memory"); \
break; \
case 8: \
- asm("xaddq %0, "__percpu_arg(1) \
+ asm qual ("xaddq %0, "__percpu_arg(1) \
: "+re" (paro_ret__), "+m" (var) \
: : "memory"); \
break; \
@@ -299,13 +299,13 @@ do { \
* expensive due to the implied lock prefix. The processor cannot prefetch
* cachelines if xchg is used.
*/
-#define percpu_xchg_op(var, nval) \
+#define percpu_xchg_op(qual, var, nval) \
({ \
typeof(var) pxo_ret__; \
typeof(var) pxo_new__ = (nval); \
switch (sizeof(var)) { \
case 1: \
- asm("\n\tmov "__percpu_arg(1)",%%al" \
+ asm qual ("\n\tmov "__percpu_arg(1)",%%al" \
"\n1:\tcmpxchgb %2, "__percpu_arg(1) \
"\n\tjnz 1b" \
: "=&a" (pxo_ret__), "+m" (var) \
@@ -313,7 +313,7 @@ do { \
: "memory"); \
break; \
case 2: \
- asm("\n\tmov "__percpu_arg(1)",%%ax" \
+ asm qual ("\n\tmov "__percpu_arg(1)",%%ax" \
"\n1:\tcmpxchgw %2, "__percpu_arg(1) \
"\n\tjnz 1b" \
: "=&a" (pxo_ret__), "+m" (var) \
@@ -321,7 +321,7 @@ do { \
: "memory"); \
break; \
case 4: \
- asm("\n\tmov "__percpu_arg(1)",%%eax" \
+ asm qual ("\n\tmov "__percpu_arg(1)",%%eax" \
"\n1:\tcmpxchgl %2, "__percpu_arg(1) \
"\n\tjnz 1b" \
: "=&a" (pxo_ret__), "+m" (var) \
@@ -329,7 +329,7 @@ do { \
: "memory"); \
break; \
case 8: \
- asm("\n\tmov "__percpu_arg(1)",%%rax" \
+ asm qual ("\n\tmov "__percpu_arg(1)",%%rax" \
"\n1:\tcmpxchgq %2, "__percpu_arg(1) \
"\n\tjnz 1b" \
: "=&a" (pxo_ret__), "+m" (var) \
@@ -345,32 +345,32 @@ do { \
* cmpxchg has no such implied lock semantics as a result it is much
* more efficient for cpu local operations.
*/
-#define percpu_cmpxchg_op(var, oval, nval) \
+#define percpu_cmpxchg_op(qual, var, oval, nval) \
({ \
typeof(var) pco_ret__; \
typeof(var) pco_old__ = (oval); \
typeof(var) pco_new__ = (nval); \
switch (sizeof(var)) { \
case 1: \
- asm("cmpxchgb %2, "__percpu_arg(1) \
+ asm qual ("cmpxchgb %2, "__percpu_arg(1) \
: "=a" (pco_ret__), "+m" (var) \
: "q" (pco_new__), "0" (pco_old__) \
: "memory"); \
break; \
case 2: \
- asm("cmpxchgw %2, "__percpu_arg(1) \
+ asm qual ("cmpxchgw %2, "__percpu_arg(1) \
: "=a" (pco_ret__), "+m" (var) \
: "r" (pco_new__), "0" (pco_old__) \
: "memory"); \
break; \
case 4: \
- asm("cmpxchgl %2, "__percpu_arg(1) \
+ asm qual ("cmpxchgl %2, "__percpu_arg(1) \
: "=a" (pco_ret__), "+m" (var) \
: "r" (pco_new__), "0" (pco_old__) \
: "memory"); \
break; \
case 8: \
- asm("cmpxchgq %2, "__percpu_arg(1) \
+ asm qual ("cmpxchgq %2, "__percpu_arg(1) \
: "=a" (pco_ret__), "+m" (var) \
: "r" (pco_new__), "0" (pco_old__) \
: "memory"); \
@@ -391,58 +391,58 @@ do { \
*/
#define this_cpu_read_stable(var) percpu_stable_op("mov", var)

-#define raw_cpu_read_1(pcp) percpu_from_op("mov", pcp)
-#define raw_cpu_read_2(pcp) percpu_from_op("mov", pcp)
-#define raw_cpu_read_4(pcp) percpu_from_op("mov", pcp)
-
-#define raw_cpu_write_1(pcp, val) percpu_to_op("mov", (pcp), val)
-#define raw_cpu_write_2(pcp, val) percpu_to_op("mov", (pcp), val)
-#define raw_cpu_write_4(pcp, val) percpu_to_op("mov", (pcp), val)
-#define raw_cpu_add_1(pcp, val) percpu_add_op((pcp), val)
-#define raw_cpu_add_2(pcp, val) percpu_add_op((pcp), val)
-#define raw_cpu_add_4(pcp, val) percpu_add_op((pcp), val)
-#define raw_cpu_and_1(pcp, val) percpu_to_op("and", (pcp), val)
-#define raw_cpu_and_2(pcp, val) percpu_to_op("and", (pcp), val)
-#define raw_cpu_and_4(pcp, val) percpu_to_op("and", (pcp), val)
-#define raw_cpu_or_1(pcp, val) percpu_to_op("or", (pcp), val)
-#define raw_cpu_or_2(pcp, val) percpu_to_op("or", (pcp), val)
-#define raw_cpu_or_4(pcp, val) percpu_to_op("or", (pcp), val)
-#define raw_cpu_xchg_1(pcp, val) percpu_xchg_op(pcp, val)
-#define raw_cpu_xchg_2(pcp, val) percpu_xchg_op(pcp, val)
-#define raw_cpu_xchg_4(pcp, val) percpu_xchg_op(pcp, val)
-
-#define this_cpu_read_1(pcp) percpu_from_op("mov", pcp)
-#define this_cpu_read_2(pcp) percpu_from_op("mov", pcp)
-#define this_cpu_read_4(pcp) percpu_from_op("mov", pcp)
-#define this_cpu_write_1(pcp, val) percpu_to_op("mov", (pcp), val)
-#define this_cpu_write_2(pcp, val) percpu_to_op("mov", (pcp), val)
-#define this_cpu_write_4(pcp, val) percpu_to_op("mov", (pcp), val)
-#define this_cpu_add_1(pcp, val) percpu_add_op((pcp), val)
-#define this_cpu_add_2(pcp, val) percpu_add_op((pcp), val)
-#define this_cpu_add_4(pcp, val) percpu_add_op((pcp), val)
-#define this_cpu_and_1(pcp, val) percpu_to_op("and", (pcp), val)
-#define this_cpu_and_2(pcp, val) percpu_to_op("and", (pcp), val)
-#define this_cpu_and_4(pcp, val) percpu_to_op("and", (pcp), val)
-#define this_cpu_or_1(pcp, val) percpu_to_op("or", (pcp), val)
-#define this_cpu_or_2(pcp, val) percpu_to_op("or", (pcp), val)
-#define this_cpu_or_4(pcp, val) percpu_to_op("or", (pcp), val)
-#define this_cpu_xchg_1(pcp, nval) percpu_xchg_op(pcp, nval)
-#define this_cpu_xchg_2(pcp, nval) percpu_xchg_op(pcp, nval)
-#define this_cpu_xchg_4(pcp, nval) percpu_xchg_op(pcp, nval)
-
-#define raw_cpu_add_return_1(pcp, val) percpu_add_return_op(pcp, val)
-#define raw_cpu_add_return_2(pcp, val) percpu_add_return_op(pcp, val)
-#define raw_cpu_add_return_4(pcp, val) percpu_add_return_op(pcp, val)
-#define raw_cpu_cmpxchg_1(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval)
-#define raw_cpu_cmpxchg_2(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval)
-#define raw_cpu_cmpxchg_4(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval)
-
-#define this_cpu_add_return_1(pcp, val) percpu_add_return_op(pcp, val)
-#define this_cpu_add_return_2(pcp, val) percpu_add_return_op(pcp, val)
-#define this_cpu_add_return_4(pcp, val) percpu_add_return_op(pcp, val)
-#define this_cpu_cmpxchg_1(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval)
-#define this_cpu_cmpxchg_2(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval)
-#define this_cpu_cmpxchg_4(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval)
+#define raw_cpu_read_1(pcp) percpu_from_op(, "mov", pcp)
+#define raw_cpu_read_2(pcp) percpu_from_op(, "mov", pcp)
+#define raw_cpu_read_4(pcp) percpu_from_op(, "mov", pcp)
+
+#define raw_cpu_write_1(pcp, val) percpu_to_op(, "mov", (pcp), val)
+#define raw_cpu_write_2(pcp, val) percpu_to_op(, "mov", (pcp), val)
+#define raw_cpu_write_4(pcp, val) percpu_to_op(, "mov", (pcp), val)
+#define raw_cpu_add_1(pcp, val) percpu_add_op(, (pcp), val)
+#define raw_cpu_add_2(pcp, val) percpu_add_op(, (pcp), val)
+#define raw_cpu_add_4(pcp, val) percpu_add_op(, (pcp), val)
+#define raw_cpu_and_1(pcp, val) percpu_to_op(, "and", (pcp), val)
+#define raw_cpu_and_2(pcp, val) percpu_to_op(, "and", (pcp), val)
+#define raw_cpu_and_4(pcp, val) percpu_to_op(, "and", (pcp), val)
+#define raw_cpu_or_1(pcp, val) percpu_to_op(, "or", (pcp), val)
+#define raw_cpu_or_2(pcp, val) percpu_to_op(, "or", (pcp), val)
+#define raw_cpu_or_4(pcp, val) percpu_to_op(, "or", (pcp), val)
+#define raw_cpu_xchg_1(pcp, val) percpu_xchg_op(, pcp, val)
+#define raw_cpu_xchg_2(pcp, val) percpu_xchg_op(, pcp, val)
+#define raw_cpu_xchg_4(pcp, val) percpu_xchg_op(, pcp, val)
+
+#define this_cpu_read_1(pcp) percpu_from_op(volatile, "mov", pcp)
+#define this_cpu_read_2(pcp) percpu_from_op(volatile, "mov", pcp)
+#define this_cpu_read_4(pcp) percpu_from_op(volatile, "mov", pcp)
+#define this_cpu_write_1(pcp, val) percpu_to_op(volatile, "mov", (pcp), val)
+#define this_cpu_write_2(pcp, val) percpu_to_op(volatile, "mov", (pcp), val)
+#define this_cpu_write_4(pcp, val) percpu_to_op(volatile, "mov", (pcp), val)
+#define this_cpu_add_1(pcp, val) percpu_add_op(volatile, (pcp), val)
+#define this_cpu_add_2(pcp, val) percpu_add_op(volatile, (pcp), val)
+#define this_cpu_add_4(pcp, val) percpu_add_op(volatile, (pcp), val)
+#define this_cpu_and_1(pcp, val) percpu_to_op(volatile, "and", (pcp), val)
+#define this_cpu_and_2(pcp, val) percpu_to_op(volatile, "and", (pcp), val)
+#define this_cpu_and_4(pcp, val) percpu_to_op(volatile, "and", (pcp), val)
+#define this_cpu_or_1(pcp, val) percpu_to_op(volatile, "or", (pcp), val)
+#define this_cpu_or_2(pcp, val) percpu_to_op(volatile, "or", (pcp), val)
+#define this_cpu_or_4(pcp, val) percpu_to_op(volatile, "or", (pcp), val)
+#define this_cpu_xchg_1(pcp, nval) percpu_xchg_op(volatile, pcp, nval)
+#define this_cpu_xchg_2(pcp, nval) percpu_xchg_op(volatile, pcp, nval)
+#define this_cpu_xchg_4(pcp, nval) percpu_xchg_op(volatile, pcp, nval)
+
+#define raw_cpu_add_return_1(pcp, val) percpu_add_return_op(, pcp, val)
+#define raw_cpu_add_return_2(pcp, val) percpu_add_return_op(, pcp, val)
+#define raw_cpu_add_return_4(pcp, val) percpu_add_return_op(, pcp, val)
+#define raw_cpu_cmpxchg_1(pcp, oval, nval) percpu_cmpxchg_op(, pcp, oval, nval)
+#define raw_cpu_cmpxchg_2(pcp, oval, nval) percpu_cmpxchg_op(, pcp, oval, nval)
+#define raw_cpu_cmpxchg_4(pcp, oval, nval) percpu_cmpxchg_op(, pcp, oval, nval)
+
+#define this_cpu_add_return_1(pcp, val) percpu_add_return_op(volatile, pcp, val)
+#define this_cpu_add_return_2(pcp, val) percpu_add_return_op(volatile, pcp, val)
+#define this_cpu_add_return_4(pcp, val) percpu_add_return_op(volatile, pcp, val)
+#define this_cpu_cmpxchg_1(pcp, oval, nval) percpu_cmpxchg_op(volatile, pcp, oval, nval)
+#define this_cpu_cmpxchg_2(pcp, oval, nval) percpu_cmpxchg_op(volatile, pcp, oval, nval)
+#define this_cpu_cmpxchg_4(pcp, oval, nval) percpu_cmpxchg_op(volatile, pcp, oval, nval)

#ifdef CONFIG_X86_CMPXCHG64
#define percpu_cmpxchg8b_double(pcp1, pcp2, o1, o2, n1, n2) \
@@ -466,23 +466,23 @@ do { \
* 32 bit must fall back to generic operations.
*/
#ifdef CONFIG_X86_64
-#define raw_cpu_read_8(pcp) percpu_from_op("mov", pcp)
-#define raw_cpu_write_8(pcp, val) percpu_to_op("mov", (pcp), val)
-#define raw_cpu_add_8(pcp, val) percpu_add_op((pcp), val)
-#define raw_cpu_and_8(pcp, val) percpu_to_op("and", (pcp), val)
-#define raw_cpu_or_8(pcp, val) percpu_to_op("or", (pcp), val)
-#define raw_cpu_add_return_8(pcp, val) percpu_add_return_op(pcp, val)
-#define raw_cpu_xchg_8(pcp, nval) percpu_xchg_op(pcp, nval)
-#define raw_cpu_cmpxchg_8(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval)
-
-#define this_cpu_read_8(pcp) percpu_from_op("mov", pcp)
-#define this_cpu_write_8(pcp, val) percpu_to_op("mov", (pcp), val)
-#define this_cpu_add_8(pcp, val) percpu_add_op((pcp), val)
-#define this_cpu_and_8(pcp, val) percpu_to_op("and", (pcp), val)
-#define this_cpu_or_8(pcp, val) percpu_to_op("or", (pcp), val)
-#define this_cpu_add_return_8(pcp, val) percpu_add_return_op(pcp, val)
-#define this_cpu_xchg_8(pcp, nval) percpu_xchg_op(pcp, nval)
-#define this_cpu_cmpxchg_8(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval)
+#define raw_cpu_read_8(pcp) percpu_from_op(, "mov", pcp)
+#define raw_cpu_write_8(pcp, val) percpu_to_op(, "mov", (pcp), val)
+#define raw_cpu_add_8(pcp, val) percpu_add_op(, (pcp), val)
+#define raw_cpu_and_8(pcp, val) percpu_to_op(, "and", (pcp), val)
+#define raw_cpu_or_8(pcp, val) percpu_to_op(, "or", (pcp), val)
+#define raw_cpu_add_return_8(pcp, val) percpu_add_return_op(, pcp, val)
+#define raw_cpu_xchg_8(pcp, nval) percpu_xchg_op(, pcp, nval)
+#define raw_cpu_cmpxchg_8(pcp, oval, nval) percpu_cmpxchg_op(, pcp, oval, nval)
+
+#define this_cpu_read_8(pcp) percpu_from_op(volatile, "mov", pcp)
+#define this_cpu_write_8(pcp, val) percpu_to_op(volatile, "mov", (pcp), val)
+#define this_cpu_add_8(pcp, val) percpu_add_op(volatile, (pcp), val)
+#define this_cpu_and_8(pcp, val) percpu_to_op(volatile, "and", (pcp), val)
+#define this_cpu_or_8(pcp, val) percpu_to_op(volatile, "or", (pcp), val)
+#define this_cpu_add_return_8(pcp, val) percpu_add_return_op(volatile, pcp, val)
+#define this_cpu_xchg_8(pcp, nval) percpu_xchg_op(volatile, pcp, nval)
+#define this_cpu_cmpxchg_8(pcp, oval, nval) percpu_cmpxchg_op(volatile, pcp, oval, nval)

/*
* Pretty complex macro to generate cmpxchg16 instruction. The instruction

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