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Commit 3226aad8 authored by Michael S. Tsirkin's avatar Michael S. Tsirkin
Browse files

sh: support 1 and 2 byte xchg 



This completes the xchg implementation for sh architecture.  Note: The
llsc variant is tricky since this only supports 4 byte atomics, the
existing implementation of 1 byte xchg is wrong: we need to do a 4 byte
cmpxchg and retry if any bytes changed meanwhile.

Write this in C for clarity.

Suggested-by: default avatarRich Felker <dalias@libc.org>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
parent a6596127

arch/sh/include/asm/cmpxchg-grb.h

+22 −0
Original line number Diff line number Diff line
@@ -23,6 +23,28 @@ static inline unsigned long xchg_u32(volatile u32 *m, unsigned long val) 
	return retval;

}



static inline unsigned long xchg_u16(volatile u16 *m, unsigned long val)

{

	unsigned long retval;



	__asm__ __volatile__ (

		"   .align  2             \n\t"

		"   mova    1f,   r0      \n\t" /* r0 = end point */

		"   mov    r15,   r1      \n\t" /* r1 = saved sp */

		"   mov    #-6,   r15     \n\t" /* LOGIN */

		"   mov.w  @%1,   %0      \n\t" /* load  old value */

		"   extu.w  %0,   %0      \n\t" /* extend as unsigned */

		"   mov.w   %2,   @%1     \n\t" /* store new value */

		"1: mov     r1,   r15     \n\t" /* LOGOUT */

		: "=&r" (retval),

		  "+r"  (m),

		  "+r"  (val)		/* inhibit r15 overloading */

		:

		: "memory" , "r0", "r1");



	return retval;

}



static inline unsigned long xchg_u8(volatile u8 *m, unsigned long val)

{

	unsigned long retval;

arch/sh/include/asm/cmpxchg-irq.h

+11 −0
Original line number Diff line number Diff line
@@ -14,6 +14,17 @@ static inline unsigned long xchg_u32(volatile u32 *m, unsigned long val) 
	return retval;

}



static inline unsigned long xchg_u16(volatile u16 *m, unsigned long val)

{

	unsigned long flags, retval;



	local_irq_save(flags);

	retval = *m;

	*m = val;

	local_irq_restore(flags);

	return retval;

}



static inline unsigned long xchg_u8(volatile u8 *m, unsigned long val)

{

	unsigned long flags, retval;

arch/sh/include/asm/cmpxchg-llsc.h

+36 −22
Original line number Diff line number Diff line 
#ifndef __ASM_SH_CMPXCHG_LLSC_H

#define __ASM_SH_CMPXCHG_LLSC_H



#include <linux/bitops.h>

#include <asm/byteorder.h>



static inline unsigned long xchg_u32(volatile u32 *m, unsigned long val)

{

	unsigned long retval;
@@ -22,29 +25,8 @@ static inline unsigned long xchg_u32(volatile u32 *m, unsigned long val) 
	return retval;

}



static inline unsigned long xchg_u8(volatile u8 *m, unsigned long val)

{

	unsigned long retval;

	unsigned long tmp;



	__asm__ __volatile__ (

		"1:					\n\t"

		"movli.l	@%2, %0	! xchg_u8	\n\t"

		"mov		%0, %1			\n\t"

		"mov		%3, %0			\n\t"

		"movco.l	%0, @%2			\n\t"

		"bf		1b			\n\t"

		"synco					\n\t"

		: "=&z"(tmp), "=&r" (retval)

		: "r" (m), "r" (val & 0xff)

		: "t", "memory"

	);



	return retval;

}



static inline unsigned long

__cmpxchg_u32(volatile int *m, unsigned long old, unsigned long new)

__cmpxchg_u32(volatile u32 *m, unsigned long old, unsigned long new)

{

	unsigned long retval;

	unsigned long tmp;
@@ -68,4 +50,36 @@ __cmpxchg_u32(volatile int *m, unsigned long old, unsigned long new) 
	return retval;

}



static inline u32 __xchg_cmpxchg(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) - 1 - 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;

}



static inline unsigned long xchg_u16(volatile u16 *m, unsigned long val)

{

	return __xchg_cmpxchg(m, val, sizeof *m);

}



static inline unsigned long xchg_u8(volatile u8 *m, unsigned long val)

{

	return __xchg_cmpxchg(m, val, sizeof *m);

}



#endif /* __ASM_SH_CMPXCHG_LLSC_H */

arch/sh/include/asm/cmpxchg.h

+3 −0
Original line number Diff line number Diff line
@@ -27,6 +27,9 @@ extern void __xchg_called_with_bad_pointer(void); 
	case 4:						\

		__xchg__res = xchg_u32(__xchg_ptr, x);	\

		break;					\

	case 2:						\

		__xchg__res = xchg_u16(__xchg_ptr, x);	\

		break;					\

	case 1:						\

		__xchg__res = xchg_u8(__xchg_ptr, x);	\

		break;					\