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xtensa: provide xchg for sizes 1 and 2 

This is required for generic queued spinlocks, implement it.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
This commit is contained in:
Max Filippov 2019-01-01 19:29:07 -08:00
parent 74d69eaadd
commit af3d890b43
1 changed files with 32 additions and 4 deletions
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36
arch/xtensa/include/asm/cmpxchg.h
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@ -13,6 +13,7 @@
#ifndef __ASSEMBLY__
#include <linux/bits.h>
#include <linux/stringify.h>
/*
@ -138,6 +139,28 @@ static inline unsigned long xchg_u32(volatile int * m, unsigned long val)
#define 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
@ -150,11 +173,16 @@ static __inline__ unsigned long
__xchg(unsigned long x, volatile void * ptr, int size)
{
switch (size) {
case 4:
return xchg_u32(ptr, x);
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;
}
__xchg_called_with_bad_pointer();
return x;
}
#endif /* __ASSEMBLY__ */