xtensa: provide xchg for sizes 1 and 2 (af3d890b) · Commits · 戴 / test

arch/xtensa/include/asm/cmpxchg.h

+32 −4

Original line number	Diff line number	Diff line
		@@ -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
		@@ -150,12 +173,17 @@ 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__ */