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Commit 1a17fdc4 authored by Andreas Larsson's avatar Andreas Larsson Committed by David S. Miller
Browse files

sparc32: Implement xchg and atomic_xchg using ATOMIC_HASH locks 



Atomicity between xchg and cmpxchg cannot be guaranteed when xchg is
implemented with a swap and cmpxchg is implemented with locks.
Without this, e.g. mcs_spin_lock and mcs_spin_unlock are broken.

Signed-off-by: default avatarAndreas Larsson <andreas@gaisler.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ab5c7809

arch/sparc/include/asm/atomic_32.h

+1 −1
Original line number Diff line number Diff line
@@ -22,7 +22,7 @@ 


int atomic_add_return(int, atomic_t *);

int atomic_cmpxchg(atomic_t *, int, int);

#define atomic_xchg(v, new) (xchg(&((v)->counter), new))

int atomic_xchg(atomic_t *, int);

int __atomic_add_unless(atomic_t *, int, int);

void atomic_set(atomic_t *, int);

arch/sparc/include/asm/cmpxchg_32.h

+2 −10
Original line number Diff line number Diff line
@@ -11,22 +11,14 @@ 
#ifndef __ARCH_SPARC_CMPXCHG__

#define __ARCH_SPARC_CMPXCHG__



static inline unsigned long xchg_u32(__volatile__ unsigned long *m, unsigned long val)

{

	__asm__ __volatile__("swap [%2], %0"

			     : "=&r" (val)

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

			     : "memory");

	return val;

}



unsigned long __xchg_u32(volatile u32 *m, u32 new);

void __xchg_called_with_bad_pointer(void);



static inline unsigned long __xchg(unsigned long x, __volatile__ void * ptr, int size)

{

	switch (size) {

	case 4:

		return xchg_u32(ptr, x);

		return __xchg_u32(ptr, x);

	}

	__xchg_called_with_bad_pointer();

	return x;

arch/sparc/lib/atomic32.c

+27 −0
Original line number Diff line number Diff line
@@ -45,6 +45,19 @@ ATOMIC_OP(add, +=) 


#undef ATOMIC_OP



int atomic_xchg(atomic_t *v, int new)

{

	int ret;

	unsigned long flags;



	spin_lock_irqsave(ATOMIC_HASH(v), flags);

	ret = v->counter;

	v->counter = new;

	spin_unlock_irqrestore(ATOMIC_HASH(v), flags);

	return ret;

}

EXPORT_SYMBOL(atomic_xchg);



int atomic_cmpxchg(atomic_t *v, int old, int new)

{

	int ret;
@@ -137,3 +150,17 @@ unsigned long __cmpxchg_u32(volatile u32 *ptr, u32 old, u32 new) 
	return (unsigned long)prev;

}

EXPORT_SYMBOL(__cmpxchg_u32);



unsigned long __xchg_u32(volatile u32 *ptr, u32 new)

{

	unsigned long flags;

	u32 prev;



	spin_lock_irqsave(ATOMIC_HASH(ptr), flags);

	prev = *ptr;

	*ptr = new;

	spin_unlock_irqrestore(ATOMIC_HASH(ptr), flags);



	return (unsigned long)prev;

}

EXPORT_SYMBOL(__xchg_u32);