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Mini Shell
Mini Shell
/*
* Atomic xchg and cmpxchg operations.
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 2001 - 2005 Tensilica Inc.
*/
#ifndef _XTENSA_CMPXCHG_H
#define _XTENSA_CMPXCHG_H
#ifndef __ASSEMBLY__
#include <linux/bits.h>
#include <linux/stringify.h>
/*
* cmpxchg
*/
static inline unsigned long
__cmpxchg_u32(volatile int *p, int old, int new)
{
#if XCHAL_HAVE_EXCLUSIVE
unsigned long tmp, result;
__asm__ __volatile__(
"1: l32ex %[result], %[addr]\n"
" bne %[result], %[cmp], 2f\n"
" mov %[tmp], %[new]\n"
" s32ex %[tmp], %[addr]\n"
" getex %[tmp]\n"
" beqz %[tmp], 1b\n"
"2:\n"
: [result] "=&a" (result), [tmp] "=&a" (tmp)
: [new] "a" (new), [addr] "a" (p), [cmp] "a" (old)
: "memory"
);
return result;
#elif XCHAL_HAVE_S32C1I
__asm__ __volatile__(
" wsr %[cmp], scompare1\n"
" s32c1i %[new], %[mem]\n"
: [new] "+a" (new), [mem] "+m" (*p)
: [cmp] "a" (old)
: "memory"
);
return new;
#else
__asm__ __volatile__(
" rsil a15, "__stringify(TOPLEVEL)"\n"
" l32i %[old], %[mem]\n"
" bne %[old], %[cmp], 1f\n"
" s32i %[new], %[mem]\n"
"1:\n"
" wsr a15, ps\n"
" rsync\n"
: [old] "=&a" (old), [mem] "+m" (*p)
: [cmp] "a" (old), [new] "r" (new)
: "a15", "memory");
return old;
#endif
}
/* This function doesn't exist, so you'll get a linker error
* if something tries to do an invalid cmpxchg(). */
extern void __cmpxchg_called_with_bad_pointer(void);
static __inline__ unsigned long
__cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size)
{
switch (size) {
case 4: return __cmpxchg_u32(ptr, old, new);
default: __cmpxchg_called_with_bad_pointer();
return old;
}
}
#define arch_cmpxchg(ptr,o,n) \
({ __typeof__(*(ptr)) _o_ = (o); \
__typeof__(*(ptr)) _n_ = (n); \
(__typeof__(*(ptr))) __cmpxchg((ptr), (unsigned long)_o_, \
(unsigned long)_n_, sizeof (*(ptr))); \
})
#include <asm-generic/cmpxchg-local.h>
static inline unsigned long __cmpxchg_local(volatile void *ptr,
unsigned long old,
unsigned long new, int size)
{
switch (size) {
case 4:
return __cmpxchg_u32(ptr, old, new);
default:
return __generic_cmpxchg_local(ptr, old, new, size);
}
return old;
}
/*
* cmpxchg_local and cmpxchg64_local are atomic wrt current CPU. Always make
* them available.
*/
#define arch_cmpxchg_local(ptr, o, n) \
((__typeof__(*(ptr)))__generic_cmpxchg_local((ptr), (unsigned long)(o),\
(unsigned long)(n), sizeof(*(ptr))))
#define arch_cmpxchg64_local(ptr, o, n) __generic_cmpxchg64_local((ptr), (o), (n))
#define arch_cmpxchg64(ptr, o, n) arch_cmpxchg64_local((ptr), (o), (n))
/*
* xchg_u32
*
* Note that a15 is used here because the register allocation
* done by the compiler is not guaranteed and a window overflow
* may not occur between the rsil and wsr instructions. By using
* a15 in the rsil, the machine is guaranteed to be in a state
* where no register reference will cause an overflow.
*/
static inline unsigned long xchg_u32(volatile int * m, unsigned long val)
{
#if XCHAL_HAVE_EXCLUSIVE
unsigned long tmp, result;
__asm__ __volatile__(
"1: l32ex %[result], %[addr]\n"
" mov %[tmp], %[val]\n"
" s32ex %[tmp], %[addr]\n"
" getex %[tmp]\n"
" beqz %[tmp], 1b\n"
: [result] "=&a" (result), [tmp] "=&a" (tmp)
: [val] "a" (val), [addr] "a" (m)
: "memory"
);
return result;
#elif XCHAL_HAVE_S32C1I
unsigned long tmp, result;
__asm__ __volatile__(
"1: l32i %[tmp], %[mem]\n"
" mov %[result], %[val]\n"
" wsr %[tmp], scompare1\n"
" s32c1i %[result], %[mem]\n"
" bne %[result], %[tmp], 1b\n"
: [result] "=&a" (result), [tmp] "=&a" (tmp),
[mem] "+m" (*m)
: [val] "a" (val)
: "memory"
);
return result;
#else
unsigned long tmp;
__asm__ __volatile__(
" rsil a15, "__stringify(TOPLEVEL)"\n"
" l32i %[tmp], %[mem]\n"
" s32i %[val], %[mem]\n"
" wsr a15, ps\n"
" rsync\n"
: [tmp] "=&a" (tmp), [mem] "+m" (*m)
: [val] "a" (val)
: "a15", "memory");
return tmp;
#endif
}
#define arch_xchg(ptr,x) \
((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr))))
static inline u32 xchg_small(volatile void *ptr, u32 x, int size)
{
int off = (unsigned long)ptr % sizeof(u32);
volatile u32 *p = ptr - off;
#ifdef __BIG_ENDIAN
int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE;
#else
int bitoff = off * BITS_PER_BYTE;
#endif
u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;
u32 oldv, newv;
u32 ret;
do {
oldv = READ_ONCE(*p);
ret = (oldv & bitmask) >> bitoff;
newv = (oldv & ~bitmask) | (x << bitoff);
} while (__cmpxchg_u32(p, oldv, newv) != oldv);
return ret;
}
/*
* This only works if the compiler isn't horribly bad at optimizing.
* gcc-2.5.8 reportedly can't handle this, but I define that one to
* be dead anyway.
*/
extern void __xchg_called_with_bad_pointer(void);
static __inline__ unsigned long
__xchg(unsigned long x, volatile void * ptr, int size)
{
switch (size) {
case 1:
return xchg_small(ptr, x, 1);
case 2:
return xchg_small(ptr, x, 2);
case 4:
return xchg_u32(ptr, x);
default:
__xchg_called_with_bad_pointer();
return x;
}
}
#endif /* __ASSEMBLY__ */
#endif /* _XTENSA_CMPXCHG_H */
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