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Subject[PATCH V2] powerpc: Implement {cmp}xchg for u8 and u16
From: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>

Implement xchg{u8,u16}{local,relaxed}, and
cmpxchg{u8,u16}{,local,acquire,relaxed}.

It works on all ppc.

Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
---
change from V1:
rework totally.
---
arch/powerpc/include/asm/cmpxchg.h | 83 ++++++++++++++++++++++++++++++++++++++
1 file changed, 83 insertions(+)

diff --git a/arch/powerpc/include/asm/cmpxchg.h b/arch/powerpc/include/asm/cmpxchg.h
index 44efe73..79a1f45 100644
--- a/arch/powerpc/include/asm/cmpxchg.h
+++ b/arch/powerpc/include/asm/cmpxchg.h
@@ -7,6 +7,37 @@
#include <asm/asm-compat.h>
#include <linux/bug.h>

+#ifdef __BIG_ENDIAN
+#define BITOFF_CAL(size, off) ((sizeof(u32) - size - off) * BITS_PER_BYTE)
+#else
+#define BITOFF_CAL(size, off) (off * BITS_PER_BYTE)
+#endif
+
+static __always_inline unsigned long
+__cmpxchg_u32_local(volatile unsigned int *p, unsigned long old,
+ unsigned long new);
+
+#define __XCHG_GEN(cmp, type, sfx, u32sfx, skip, v) \
+static __always_inline u32 \
+__##cmp##xchg_##type##sfx(v void *ptr, u32 old, u32 new) \
+{ \
+ int size = sizeof (type); \
+ int off = (unsigned long)ptr % sizeof(u32); \
+ volatile u32 *p = ptr - off; \
+ int bitoff = BITOFF_CAL(size, off); \
+ u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff; \
+ u32 oldv, newv; \
+ u32 ret; \
+ do { \
+ oldv = READ_ONCE(*p); \
+ ret = (oldv & bitmask) >> bitoff; \
+ if (skip && ret != old) \
+ break; \
+ newv = (oldv & ~bitmask) | (new << bitoff); \
+ } while (__cmpxchg_u32##u32sfx((v void*)p, oldv, newv) != oldv);\
+ return ret; \
+}
+
/*
* Atomic exchange
*
@@ -14,6 +45,19 @@
* the previous value stored there.
*/

+#define XCHG_GEN(type, sfx, v) \
+ __XCHG_GEN(_, type, sfx, _local, 0, v) \
+static __always_inline u32 __xchg_##type##sfx(v void *p, u32 n) \
+{ \
+ return ___xchg_##type##sfx(p, 0, n); \
+}
+
+XCHG_GEN(u8, _local, volatile);
+XCHG_GEN(u8, _relaxed, );
+XCHG_GEN(u16, _local, volatile);
+XCHG_GEN(u16, _relaxed, );
+#undef XCHG_GEN
+
static __always_inline unsigned long
__xchg_u32_local(volatile void *p, unsigned long val)
{
@@ -88,6 +132,10 @@ static __always_inline unsigned long
__xchg_local(volatile void *ptr, unsigned long x, unsigned int size)
{
switch (size) {
+ case 1:
+ return __xchg_u8_local(ptr, x);
+ case 2:
+ return __xchg_u16_local(ptr, x);
case 4:
return __xchg_u32_local(ptr, x);
#ifdef CONFIG_PPC64
@@ -103,6 +151,10 @@ static __always_inline unsigned long
__xchg_relaxed(void *ptr, unsigned long x, unsigned int size)
{
switch (size) {
+ case 1:
+ return __xchg_u8_relaxed(ptr, x);
+ case 2:
+ return __xchg_u16_relaxed(ptr, x);
case 4:
return __xchg_u32_relaxed(ptr, x);
#ifdef CONFIG_PPC64
@@ -226,6 +278,21 @@ __cmpxchg_u32_acquire(u32 *p, unsigned long old, unsigned long new)
return prev;
}

+
+#define CMPXCHG_GEN(type, sfx, v) \
+ __XCHG_GEN(cmp, type, sfx, sfx, 1, v)
+
+CMPXCHG_GEN(u8, , volatile);
+CMPXCHG_GEN(u8, _local, volatile);
+CMPXCHG_GEN(u8, _relaxed, );
+CMPXCHG_GEN(u8, _acquire, );
+CMPXCHG_GEN(u16, , volatile);
+CMPXCHG_GEN(u16, _local, volatile);
+CMPXCHG_GEN(u16, _relaxed, );
+CMPXCHG_GEN(u16, _acquire, );
+#undef CMPXCHG_GEN
+#undef __XCHG_GEN
+
#ifdef CONFIG_PPC64
static __always_inline unsigned long
__cmpxchg_u64(volatile unsigned long *p, unsigned long old, unsigned long new)
@@ -316,6 +383,10 @@ __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new,
unsigned int size)
{
switch (size) {
+ case 1:
+ return __cmpxchg_u8(ptr, old, new);
+ case 2:
+ return __cmpxchg_u16(ptr, old, new);
case 4:
return __cmpxchg_u32(ptr, old, new);
#ifdef CONFIG_PPC64
@@ -332,6 +403,10 @@ __cmpxchg_local(volatile void *ptr, unsigned long old, unsigned long new,
unsigned int size)
{
switch (size) {
+ case 1:
+ return __cmpxchg_u8_local(ptr, old, new);
+ case 2:
+ return __cmpxchg_u16_local(ptr, old, new);
case 4:
return __cmpxchg_u32_local(ptr, old, new);
#ifdef CONFIG_PPC64
@@ -348,6 +423,10 @@ __cmpxchg_relaxed(void *ptr, unsigned long old, unsigned long new,
unsigned int size)
{
switch (size) {
+ case 1:
+ return __cmpxchg_u8_relaxed(ptr, old, new);
+ case 2:
+ return __cmpxchg_u16_relaxed(ptr, old, new);
case 4:
return __cmpxchg_u32_relaxed(ptr, old, new);
#ifdef CONFIG_PPC64
@@ -364,6 +443,10 @@ __cmpxchg_acquire(void *ptr, unsigned long old, unsigned long new,
unsigned int size)
{
switch (size) {
+ case 1:
+ return __cmpxchg_u8_acquire(ptr, old, new);
+ case 2:
+ return __cmpxchg_u16_acquire(ptr, old, new);
case 4:
return __cmpxchg_u32_acquire(ptr, old, new);
#ifdef CONFIG_PPC64
--
2.4.3
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