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: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Boqun Feng
Michael Ellerman
parent
26760fc19a
commit
56c08e6d22
2 changed files with 158 additions and 1 deletions
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@ -176,6 +176,11 @@ static __inline__ int atomic_dec_return_relaxed(atomic_t *v)
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#define atomic_dec_return_relaxed atomic_dec_return_relaxed
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#define atomic_cmpxchg(v, o, n) (cmpxchg(&((v)->counter), (o), (n)))
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#define atomic_cmpxchg_relaxed(v, o, n) \
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cmpxchg_relaxed(&((v)->counter), (o), (n))
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#define atomic_cmpxchg_acquire(v, o, n) \
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cmpxchg_acquire(&((v)->counter), (o), (n))
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#define atomic_xchg(v, new) (xchg(&((v)->counter), new))
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#define atomic_xchg_relaxed(v, new) xchg_relaxed(&((v)->counter), (new))
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@ -444,6 +449,11 @@ static __inline__ long atomic64_dec_if_positive(atomic64_t *v)
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}
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#define atomic64_cmpxchg(v, o, n) (cmpxchg(&((v)->counter), (o), (n)))
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#define atomic64_cmpxchg_relaxed(v, o, n) \
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cmpxchg_relaxed(&((v)->counter), (o), (n))
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#define atomic64_cmpxchg_acquire(v, o, n) \
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cmpxchg_acquire(&((v)->counter), (o), (n))
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#define atomic64_xchg(v, new) (xchg(&((v)->counter), new))
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#define atomic64_xchg_relaxed(v, new) xchg_relaxed(&((v)->counter), (new))
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@ -181,6 +181,56 @@ __cmpxchg_u32_local(volatile unsigned int *p, unsigned long old,
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return prev;
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}
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static __always_inline unsigned long
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__cmpxchg_u32_relaxed(u32 *p, unsigned long old, unsigned long new)
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{
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unsigned long prev;
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__asm__ __volatile__ (
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"1: lwarx %0,0,%2 # __cmpxchg_u32_relaxed\n"
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" cmpw 0,%0,%3\n"
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" bne- 2f\n"
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PPC405_ERR77(0, %2)
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" stwcx. %4,0,%2\n"
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" bne- 1b\n"
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"2:"
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: "=&r" (prev), "+m" (*p)
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: "r" (p), "r" (old), "r" (new)
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: "cc");
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return prev;
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}
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/*
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* cmpxchg family don't have order guarantee if cmp part fails, therefore we
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* can avoid superfluous barriers if we use assembly code to implement
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* cmpxchg() and cmpxchg_acquire(), however we don't do the similar for
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* cmpxchg_release() because that will result in putting a barrier in the
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* middle of a ll/sc loop, which is probably a bad idea. For example, this
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* might cause the conditional store more likely to fail.
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*/
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static __always_inline unsigned long
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__cmpxchg_u32_acquire(u32 *p, unsigned long old, unsigned long new)
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{
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unsigned long prev;
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__asm__ __volatile__ (
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"1: lwarx %0,0,%2 # __cmpxchg_u32_acquire\n"
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" cmpw 0,%0,%3\n"
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" bne- 2f\n"
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PPC405_ERR77(0, %2)
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" stwcx. %4,0,%2\n"
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" bne- 1b\n"
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PPC_ACQUIRE_BARRIER
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"\n"
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"2:"
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: "=&r" (prev), "+m" (*p)
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: "r" (p), "r" (old), "r" (new)
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: "cc", "memory");
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return prev;
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}
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#ifdef CONFIG_PPC64
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static __always_inline unsigned long
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__cmpxchg_u64(volatile unsigned long *p, unsigned long old, unsigned long new)
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@ -224,6 +274,46 @@ __cmpxchg_u64_local(volatile unsigned long *p, unsigned long old,
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return prev;
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}
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static __always_inline unsigned long
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__cmpxchg_u64_relaxed(u64 *p, unsigned long old, unsigned long new)
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{
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unsigned long prev;
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__asm__ __volatile__ (
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"1: ldarx %0,0,%2 # __cmpxchg_u64_relaxed\n"
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" cmpd 0,%0,%3\n"
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" bne- 2f\n"
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" stdcx. %4,0,%2\n"
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" bne- 1b\n"
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"2:"
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: "=&r" (prev), "+m" (*p)
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: "r" (p), "r" (old), "r" (new)
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: "cc");
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return prev;
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}
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static __always_inline unsigned long
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__cmpxchg_u64_acquire(u64 *p, unsigned long old, unsigned long new)
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{
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unsigned long prev;
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__asm__ __volatile__ (
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"1: ldarx %0,0,%2 # __cmpxchg_u64_acquire\n"
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" cmpd 0,%0,%3\n"
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" bne- 2f\n"
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" stdcx. %4,0,%2\n"
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" bne- 1b\n"
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PPC_ACQUIRE_BARRIER
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"\n"
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"2:"
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: "=&r" (prev), "+m" (*p)
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: "r" (p), "r" (old), "r" (new)
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: "cc", "memory");
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return prev;
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}
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#endif
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/* This function doesn't exist, so you'll get a linker error
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@ -262,6 +352,37 @@ __cmpxchg_local(volatile void *ptr, unsigned long old, unsigned long new,
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return old;
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}
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static __always_inline unsigned long
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__cmpxchg_relaxed(void *ptr, unsigned long old, unsigned long new,
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unsigned int size)
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{
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switch (size) {
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case 4:
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return __cmpxchg_u32_relaxed(ptr, old, new);
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#ifdef CONFIG_PPC64
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case 8:
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return __cmpxchg_u64_relaxed(ptr, old, new);
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#endif
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}
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__cmpxchg_called_with_bad_pointer();
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return old;
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}
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static __always_inline unsigned long
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__cmpxchg_acquire(void *ptr, unsigned long old, unsigned long new,
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unsigned int size)
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{
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switch (size) {
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case 4:
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return __cmpxchg_u32_acquire(ptr, old, new);
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#ifdef CONFIG_PPC64
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case 8:
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return __cmpxchg_u64_acquire(ptr, old, new);
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#endif
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}
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__cmpxchg_called_with_bad_pointer();
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return old;
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}
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#define cmpxchg(ptr, o, n) \
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({ \
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__typeof__(*(ptr)) _o_ = (o); \
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@ -279,6 +400,23 @@ __cmpxchg_local(volatile void *ptr, unsigned long old, unsigned long new,
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(unsigned long)_n_, sizeof(*(ptr))); \
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})
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#define cmpxchg_relaxed(ptr, o, n) \
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({ \
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__typeof__(*(ptr)) _o_ = (o); \
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__typeof__(*(ptr)) _n_ = (n); \
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(__typeof__(*(ptr))) __cmpxchg_relaxed((ptr), \
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(unsigned long)_o_, (unsigned long)_n_, \
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sizeof(*(ptr))); \
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})
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#define cmpxchg_acquire(ptr, o, n) \
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({ \
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__typeof__(*(ptr)) _o_ = (o); \
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__typeof__(*(ptr)) _n_ = (n); \
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(__typeof__(*(ptr))) __cmpxchg_acquire((ptr), \
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(unsigned long)_o_, (unsigned long)_n_, \
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sizeof(*(ptr))); \
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})
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#ifdef CONFIG_PPC64
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#define cmpxchg64(ptr, o, n) \
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({ \
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@ -290,7 +428,16 @@ __cmpxchg_local(volatile void *ptr, unsigned long old, unsigned long new,
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BUILD_BUG_ON(sizeof(*(ptr)) != 8); \
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cmpxchg_local((ptr), (o), (n)); \
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})
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#define cmpxchg64_relaxed cmpxchg64_local
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#define cmpxchg64_relaxed(ptr, o, n) \
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({ \
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BUILD_BUG_ON(sizeof(*(ptr)) != 8); \
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cmpxchg_relaxed((ptr), (o), (n)); \
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})
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#define cmpxchg64_acquire(ptr, o, n) \
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({ \
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BUILD_BUG_ON(sizeof(*(ptr)) != 8); \
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cmpxchg_acquire((ptr), (o), (n)); \
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})
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#else
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#include <asm-generic/cmpxchg-local.h>
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#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
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