Subject: Re: [PATCH] make atomic_t volatile on all architectures

From: Martin Schwidefsky <[email-masked]>
Date: Thu, 09 Aug 2007 19:57:55 +0200

On Thu, 2007-08-09 at 13:36 -0400, Chuck Ebbert wrote:
> > Fair enough.  Casting to (volatile int *) will give us the behavior
> > people expect when using atomic_t without needing to use inefficient
> > barriers.
> > 
> 
> You can use this forget() macro to make the compiler reread a
> variable:
> 
> #define forget(var) asm volatile ("" : "=m"(var))

You need to specify a "m"(var) input constraint as well. Without it the
compiler might remove the initialization of var. E.g.

void fn(void)
{
	int var = 0;
	forget(var);
	/* now var can have any value. */
}

-- 
blue skies,
  Martin.

"Reality continues to ruin my life." - Calvin.