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powerpc: Make {cmp}xchg* and their atomic_ versions fully ordered 

According to memory-barriers.txt, xchg*, cmpxchg* and their atomic_
versions all need to be fully ordered, however they are now just
RELEASE+ACQUIRE, which are not fully ordered.

So also replace PPC_RELEASE_BARRIER and PPC_ACQUIRE_BARRIER with
PPC_ATOMIC_ENTRY_BARRIER and PPC_ATOMIC_EXIT_BARRIER in
__{cmp,}xchg_{u32,u64} respectively to guarantee fully ordered semantics
of atomic{,64}_{cmp,}xchg() and {cmp,}xchg(), as a complement of commit
b97021f855 ("powerpc: Fix atomic_xxx_return barrier semantics")

This patch depends on patch "powerpc: Make value-returning atomics fully
ordered" for PPC_ATOMIC_ENTRY_BARRIER definition.

Cc: stable@vger.kernel.org # 3.2+
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Boqun Feng 2015-11-02 09:30:32 +08:00 committed by Michael Ellerman
parent 49e9cf3f0c
commit 81d7a3294d
1 changed files with 8 additions and 8 deletions
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16
arch/powerpc/include/asm/cmpxchg.h
View File

@ -18,12 +18,12 @@ __xchg_u32(volatile void *p, unsigned long val)
unsigned long prev;
__asm__ __volatile__(
PPC_RELEASE_BARRIER
PPC_ATOMIC_ENTRY_BARRIER
"1: lwarx %0,0,%2 \n"
PPC405_ERR77(0,%2)
" stwcx. %3,0,%2 \n\
bne- 1b"
PPC_ACQUIRE_BARRIER
PPC_ATOMIC_EXIT_BARRIER
: "=&r" (prev), "+m" (*(volatile unsigned int *)p)
: "r" (p), "r" (val)
: "cc", "memory");
@ -61,12 +61,12 @@ __xchg_u64(volatile void *p, unsigned long val)
unsigned long prev;
__asm__ __volatile__(
PPC_RELEASE_BARRIER
PPC_ATOMIC_ENTRY_BARRIER
"1: ldarx %0,0,%2 \n"
PPC405_ERR77(0,%2)
" stdcx. %3,0,%2 \n\
bne- 1b"
PPC_ACQUIRE_BARRIER
PPC_ATOMIC_EXIT_BARRIER
: "=&r" (prev), "+m" (*(volatile unsigned long *)p)
: "r" (p), "r" (val)
: "cc", "memory");
@ -151,14 +151,14 @@ __cmpxchg_u32(volatile unsigned int *p, unsigned long old, unsigned long new)
unsigned int prev;
__asm__ __volatile__ (
PPC_RELEASE_BARRIER
PPC_ATOMIC_ENTRY_BARRIER
"1: lwarx %0,0,%2 # __cmpxchg_u32\n\
cmpw 0,%0,%3\n\
bne- 2f\n"
PPC405_ERR77(0,%2)
" stwcx. %4,0,%2\n\
bne- 1b"
PPC_ACQUIRE_BARRIER
PPC_ATOMIC_EXIT_BARRIER
"\n\
2:"
: "=&r" (prev), "+m" (*p)
@ -197,13 +197,13 @@ __cmpxchg_u64(volatile unsigned long *p, unsigned long old, unsigned long new)
unsigned long prev;
__asm__ __volatile__ (
PPC_RELEASE_BARRIER
PPC_ATOMIC_ENTRY_BARRIER
"1: ldarx %0,0,%2 # __cmpxchg_u64\n\
cmpd 0,%0,%3\n\
bne- 2f\n\
stdcx. %4,0,%2\n\
bne- 1b"
PPC_ACQUIRE_BARRIER
PPC_ATOMIC_EXIT_BARRIER
"\n\
2:"
: "=&r" (prev), "+m" (*p)