Commit 56c08e6d authored by Boqun Feng's avatar Boqun Feng Committed by Michael Ellerman

powerpc: atomic: Implement acquire/release/relaxed variants for cmpxchg

Implement cmpxchg{,64}_relaxed and atomic{,64}_cmpxchg_relaxed, based on
which _release variants can be built.

To avoid superfluous barriers in _acquire variants, we implement these
operations with assembly code rather use __atomic_op_acquire() to build
them automatically.

For the same reason, we keep the assembly implementation of fully
ordered cmpxchg operations.

However, we don't do the similar for _release, because that will require
putting barriers in the middle of ll/sc loops, which is probably a bad
idea.

Note cmpxchg{,64}_relaxed and atomic{,64}_cmpxchg_relaxed are not
compiler barriers.
Signed-off-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 26760fc1
......@@ -176,6 +176,11 @@ static __inline__ int atomic_dec_return_relaxed(atomic_t *v)
#define atomic_dec_return_relaxed atomic_dec_return_relaxed
#define atomic_cmpxchg(v, o, n) (cmpxchg(&((v)->counter), (o), (n)))
#define atomic_cmpxchg_relaxed(v, o, n) \
cmpxchg_relaxed(&((v)->counter), (o), (n))
#define atomic_cmpxchg_acquire(v, o, n) \
cmpxchg_acquire(&((v)->counter), (o), (n))
#define atomic_xchg(v, new) (xchg(&((v)->counter), new))
#define atomic_xchg_relaxed(v, new) xchg_relaxed(&((v)->counter), (new))
......@@ -444,6 +449,11 @@ static __inline__ long atomic64_dec_if_positive(atomic64_t *v)
}
#define atomic64_cmpxchg(v, o, n) (cmpxchg(&((v)->counter), (o), (n)))
#define atomic64_cmpxchg_relaxed(v, o, n) \
cmpxchg_relaxed(&((v)->counter), (o), (n))
#define atomic64_cmpxchg_acquire(v, o, n) \
cmpxchg_acquire(&((v)->counter), (o), (n))
#define atomic64_xchg(v, new) (xchg(&((v)->counter), new))
#define atomic64_xchg_relaxed(v, new) xchg_relaxed(&((v)->counter), (new))
......
......@@ -181,6 +181,56 @@ __cmpxchg_u32_local(volatile unsigned int *p, unsigned long old,
return prev;
}
static __always_inline unsigned long
__cmpxchg_u32_relaxed(u32 *p, unsigned long old, unsigned long new)
{
unsigned long prev;
__asm__ __volatile__ (
"1: lwarx %0,0,%2 # __cmpxchg_u32_relaxed\n"
" cmpw 0,%0,%3\n"
" bne- 2f\n"
PPC405_ERR77(0, %2)
" stwcx. %4,0,%2\n"
" bne- 1b\n"
"2:"
: "=&r" (prev), "+m" (*p)
: "r" (p), "r" (old), "r" (new)
: "cc");
return prev;
}
/*
* cmpxchg family don't have order guarantee if cmp part fails, therefore we
* can avoid superfluous barriers if we use assembly code to implement
* cmpxchg() and cmpxchg_acquire(), however we don't do the similar for
* cmpxchg_release() because that will result in putting a barrier in the
* middle of a ll/sc loop, which is probably a bad idea. For example, this
* might cause the conditional store more likely to fail.
*/
static __always_inline unsigned long
__cmpxchg_u32_acquire(u32 *p, unsigned long old, unsigned long new)
{
unsigned long prev;
__asm__ __volatile__ (
"1: lwarx %0,0,%2 # __cmpxchg_u32_acquire\n"
" cmpw 0,%0,%3\n"
" bne- 2f\n"
PPC405_ERR77(0, %2)
" stwcx. %4,0,%2\n"
" bne- 1b\n"
PPC_ACQUIRE_BARRIER
"\n"
"2:"
: "=&r" (prev), "+m" (*p)
: "r" (p), "r" (old), "r" (new)
: "cc", "memory");
return prev;
}
#ifdef CONFIG_PPC64
static __always_inline unsigned long
__cmpxchg_u64(volatile unsigned long *p, unsigned long old, unsigned long new)
......@@ -224,6 +274,46 @@ __cmpxchg_u64_local(volatile unsigned long *p, unsigned long old,
return prev;
}
static __always_inline unsigned long
__cmpxchg_u64_relaxed(u64 *p, unsigned long old, unsigned long new)
{
unsigned long prev;
__asm__ __volatile__ (
"1: ldarx %0,0,%2 # __cmpxchg_u64_relaxed\n"
" cmpd 0,%0,%3\n"
" bne- 2f\n"
" stdcx. %4,0,%2\n"
" bne- 1b\n"
"2:"
: "=&r" (prev), "+m" (*p)
: "r" (p), "r" (old), "r" (new)
: "cc");
return prev;
}
static __always_inline unsigned long
__cmpxchg_u64_acquire(u64 *p, unsigned long old, unsigned long new)
{
unsigned long prev;
__asm__ __volatile__ (
"1: ldarx %0,0,%2 # __cmpxchg_u64_acquire\n"
" cmpd 0,%0,%3\n"
" bne- 2f\n"
" stdcx. %4,0,%2\n"
" bne- 1b\n"
PPC_ACQUIRE_BARRIER
"\n"
"2:"
: "=&r" (prev), "+m" (*p)
: "r" (p), "r" (old), "r" (new)
: "cc", "memory");
return prev;
}
#endif
/* This function doesn't exist, so you'll get a linker error
......@@ -262,6 +352,37 @@ __cmpxchg_local(volatile void *ptr, unsigned long old, unsigned long new,
return old;
}
static __always_inline unsigned long
__cmpxchg_relaxed(void *ptr, unsigned long old, unsigned long new,
unsigned int size)
{
switch (size) {
case 4:
return __cmpxchg_u32_relaxed(ptr, old, new);
#ifdef CONFIG_PPC64
case 8:
return __cmpxchg_u64_relaxed(ptr, old, new);
#endif
}
__cmpxchg_called_with_bad_pointer();
return old;
}
static __always_inline unsigned long
__cmpxchg_acquire(void *ptr, unsigned long old, unsigned long new,
unsigned int size)
{
switch (size) {
case 4:
return __cmpxchg_u32_acquire(ptr, old, new);
#ifdef CONFIG_PPC64
case 8:
return __cmpxchg_u64_acquire(ptr, old, new);
#endif
}
__cmpxchg_called_with_bad_pointer();
return old;
}
#define cmpxchg(ptr, o, n) \
({ \
__typeof__(*(ptr)) _o_ = (o); \
......@@ -279,6 +400,23 @@ __cmpxchg_local(volatile void *ptr, unsigned long old, unsigned long new,
(unsigned long)_n_, sizeof(*(ptr))); \
})
#define cmpxchg_relaxed(ptr, o, n) \
({ \
__typeof__(*(ptr)) _o_ = (o); \
__typeof__(*(ptr)) _n_ = (n); \
(__typeof__(*(ptr))) __cmpxchg_relaxed((ptr), \
(unsigned long)_o_, (unsigned long)_n_, \
sizeof(*(ptr))); \
})
#define cmpxchg_acquire(ptr, o, n) \
({ \
__typeof__(*(ptr)) _o_ = (o); \
__typeof__(*(ptr)) _n_ = (n); \
(__typeof__(*(ptr))) __cmpxchg_acquire((ptr), \
(unsigned long)_o_, (unsigned long)_n_, \
sizeof(*(ptr))); \
})
#ifdef CONFIG_PPC64
#define cmpxchg64(ptr, o, n) \
({ \
......@@ -290,7 +428,16 @@ __cmpxchg_local(volatile void *ptr, unsigned long old, unsigned long new,
BUILD_BUG_ON(sizeof(*(ptr)) != 8); \
cmpxchg_local((ptr), (o), (n)); \
})
#define cmpxchg64_relaxed cmpxchg64_local
#define cmpxchg64_relaxed(ptr, o, n) \
({ \
BUILD_BUG_ON(sizeof(*(ptr)) != 8); \
cmpxchg_relaxed((ptr), (o), (n)); \
})
#define cmpxchg64_acquire(ptr, o, n) \
({ \
BUILD_BUG_ON(sizeof(*(ptr)) != 8); \
cmpxchg_acquire((ptr), (o), (n)); \
})
#else
#include <asm-generic/cmpxchg-local.h>
#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
......
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