On Wed, Apr 27, 2016 at 05:16:45PM +0800, Pan Xinhui wrote: > From: Pan Xinhui <[email protected]> > > Implement xchg{u8,u16}{local,relaxed}, and > cmpxchg{u8,u16}{,local,acquire,relaxed}. > > It works on all ppc. > > remove volatile of first parameter in __cmpxchg_local and __cmpxchg > > Suggested-by: Peter Zijlstra (Intel) <[email protected]> > Signed-off-by: Pan Xinhui <[email protected]> > --- > change from v3: > rewrite in asm for the LL/SC. > remove volatile in __cmpxchg_local and __cmpxchg. > change from v2: > in the do{}while(), we save one load and use corresponding cmpxchg > suffix. > Also add corresponding __cmpxchg_u32 function declaration in the > __XCHG_GEN > change from V1: > rework totally. > --- > arch/powerpc/include/asm/cmpxchg.h | 109 > ++++++++++++++++++++++++++++++++++++- > 1 file changed, 106 insertions(+), 3 deletions(-) > > diff --git a/arch/powerpc/include/asm/cmpxchg.h > b/arch/powerpc/include/asm/cmpxchg.h > index 44efe73..8a3735f 100644 > --- a/arch/powerpc/include/asm/cmpxchg.h > +++ b/arch/powerpc/include/asm/cmpxchg.h > @@ -7,6 +7,71 @@ > #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 > + > +#define XCHG_GEN(type, sfx, cl) \ > +static inline u32 __xchg_##type##sfx(void *p, u32 val) \ > +{ \ > + unsigned int prev, prev_mask, tmp, bitoff, off; \ > + \ > + off = (unsigned long)p % sizeof(u32); \ > + bitoff = BITOFF_CAL(sizeof(type), off); \ > + p -= off; \ > + val <<= bitoff; \ > + prev_mask = (u32)(type)-1 << bitoff; \ > + \ > + __asm__ __volatile__( \ > +"1: lwarx %0,0,%3\n" \ > +" andc %1,%0,%5\n" \ > +" or %1,%1,%4\n" \ > + PPC405_ERR77(0,%3) \ > +" stwcx. %1,0,%3\n" \ > +" bne- 1b\n" \ > + : "=&r" (prev), "=&r" (tmp), "+m" (*(u32*)p) \
I think we can save the "tmp" here by:
__asm__ volatile__(
"1: lwarx %0,0,%2\n"
" andc %0,%0,%4\n"
" or %0,%0,%3\n"
PPC405_ERR77(0,%2)
" stwcx. %0,0,%2\n"
" bne- 1b\n"
: "=&r" (prev), "+m" (*(u32*)p)
: "r" (p), "r" (val), "r" (prev_mask)
: "cc", cl);
right?
> + : "r" (p), "r" (val), "r" (prev_mask) \
> + : "cc", cl); \
> + \
> + return prev >> bitoff; \
> +}
> +
> +#define CMPXCHG_GEN(type, sfx, br, br2, cl) \
> +static inline \
> +u32 __cmpxchg_##type##sfx(void *p, u32 old, u32 new) \
> +{ \
> + unsigned int prev, prev_mask, tmp, bitoff, off; \
> + \
> + off = (unsigned long)p % sizeof(u32); \
> + bitoff = BITOFF_CAL(sizeof(type), off); \
> + p -= off; \
> + old <<= bitoff; \
> + new <<= bitoff; \
> + prev_mask = (u32)(type)-1 << bitoff; \
> + \
> + __asm__ __volatile__( \
> + br \
> +"1: lwarx %0,0,%3\n" \
> +" and %1,%0,%6\n" \
> +" cmpw 0,%1,%4\n" \
> +" bne- 2f\n" \
> +" andc %1,%0,%6\n" \
> +" or %1,%1,%5\n" \
> + PPC405_ERR77(0,%3) \
> +" stwcx. %1,0,%3\n" \
> +" bne- 1b\n" \
> + br2 \
> + "\n" \
> +"2:" \
> + : "=&r" (prev), "=&r" (tmp), "+m" (*(u32*)p) \
And "tmp" here could also be saved by:
"1: lwarx %0,0,%2\n" \
" xor %3,%0,%3\n" \
" and. %3,%3,%5\n" \
" bne- 2f\n" \
" andc %0,%0,%5\n" \
" or %0,%0,%4\n" \
PPC405_ERR77(0,%2) \
" stwcx. %0,0,%2\n" \
" bne- 1b\n" \
br2 \
"\n" \
"2:" \
: "=&r" (prev), "+m" (*(u32*)p) \
: "r" (p), "r" (old), "r" (new), "r" (prev_mask) \
: "cc", cl); \
right?
IIUC, saving the local variable "tmp" will result in saving a general
register for the compilers to use for other variables.
So thoughts?
Regards,
Boqun
> + : "r" (p), "r" (old), "r" (new), "r" (prev_mask) \
> + : "cc", cl); \
> + \
> + return prev >> bitoff; \
> +}
> +
> /*
> * Atomic exchange
> *
> @@ -14,6 +79,11 @@
> * the previous value stored there.
> */
>
> +XCHG_GEN(u8, _local, "memory");
> +XCHG_GEN(u8, _relaxed, "cc");
> +XCHG_GEN(u16, _local, "memory");
> +XCHG_GEN(u16, _relaxed, "cc");
> +
> static __always_inline unsigned long
> __xchg_u32_local(volatile void *p, unsigned long val)
> {
> @@ -85,9 +155,13 @@ __xchg_u64_relaxed(u64 *p, unsigned long val)
> #endif
>
> static __always_inline unsigned long
> -__xchg_local(volatile void *ptr, unsigned long x, unsigned int size)
> +__xchg_local(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 +177,10 @@ 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
> @@ -131,6 +209,15 @@ __xchg_relaxed(void *ptr, unsigned long x, unsigned int
> size)
> * and return the old value of *p.
> */
>
> +CMPXCHG_GEN(u8, , PPC_ATOMIC_ENTRY_BARRIER, PPC_ATOMIC_EXIT_BARRIER,
> "memory");
> +CMPXCHG_GEN(u8, _local, , , "memory");
> +CMPXCHG_GEN(u8, _acquire, , PPC_ACQUIRE_BARRIER, "memory");
> +CMPXCHG_GEN(u8, _relaxed, , , "cc");
> +CMPXCHG_GEN(u16, , PPC_ATOMIC_ENTRY_BARRIER, PPC_ATOMIC_EXIT_BARRIER,
> "memory");
> +CMPXCHG_GEN(u16, _local, , , "memory");
> +CMPXCHG_GEN(u16, _acquire, , PPC_ACQUIRE_BARRIER, "memory");
> +CMPXCHG_GEN(u16, _relaxed, , , "cc");
> +
> static __always_inline unsigned long
> __cmpxchg_u32(volatile unsigned int *p, unsigned long old, unsigned long new)
> {
> @@ -312,10 +399,14 @@ __cmpxchg_u64_acquire(u64 *p, unsigned long old,
> unsigned long new)
> #endif
>
> static __always_inline unsigned long
> -__cmpxchg(volatile void *ptr, unsigned long old, unsigned long new,
> +__cmpxchg(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
> @@ -328,10 +419,14 @@ __cmpxchg(volatile void *ptr, unsigned long old,
> unsigned long new,
> }
>
> static __always_inline unsigned long
> -__cmpxchg_local(volatile void *ptr, unsigned long old, unsigned long new,
> +__cmpxchg_local(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 +443,10 @@ __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 +463,10 @@ __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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