Re: set_bit() is broken on i386?

[Trond Myklebust]

On Fri, 2006-01-20 at 19:53 -0500, Chuck Ebbert wrote:

> #define ADDR (*(volatile long *) addr)
> static inline void set_bit(int nr, volatile unsigned long * addr)
> {
> 	__asm__ __volatile__( "lock ; "
> 		"btsl %1,%0"
> 		:"=m" (ADDR)
> 		:"Ir" (nr));
> }

The asm needs a memory clobber in order to avoid reordering with the
assignment to b[1]:

static inline void set_bit(int nr, volatile unsigned long * addr)
{
	__asm__ __volatile__( "lock ; "
		"btsl %1,%0"
		:"=m" (ADDR)
		:"Ir" (nr)
		: "memory");
}

This works consistently correctly for me.

Cheers,
  Trond

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/