COMPARE_AND_EXCHANGE for linux-powerpc

[Edouard G. Parmelan]

Carlos Valiente wrote:

> On Friday 23 February 2001 10:32, Edouard G. Parmelan wrote:
> 
> > > I've copied and pasted the C version of COMPARE_AND_EXCHANGE from
> > > config/mips/common.h and everything seems to work OK.
> >
> > Be careful, this C version will only work with unix-jthread subsystem.
> 
> Oops, I hadn't thought about it :-( What would be a cleaner solution? Perhaps 
> an implementation in PowerPC assembler?

Yep.  Could you test this:

/*
 * Do an atomic compare and exchange.  The address 'A' is checked against 
 * value 'O' and if they match it's exchanged with value 'N'.
 * We return '1' if the exchange is sucessful, otherwise 0.
 */
#define COMPARE_AND_EXCHANGE(A,O,N)		\
({						\
	int tmp, ret = 0;			\
						\
	asm volatile(				\
	"1:	lwarx	%0,0,%3\n"		\
	"	cmpw	0,%0,%4\n"		\
	"	bne	2f\n"			\
	"	stwcx	%5,0,%3\n"		\
	"	bne-	1b\n"			\
	"	sync\n"				\
	"	li	%1,1\n"			\
	"2:\n"					\
	: "=&r"(tmp), "=&r"(ret), "=m"(*(A))	\
	: "r"(A), "r"(O), "r"(N), "m"(*(A))	\
	: "cc", "memory");			\
						\
	ret;					\
})

-- 
Edouard G. Parmelan
http://egp.free.fr