Re: [PATCH] Use CC atomic builtins if available [was: Re: TAS patch for building on armel/armhf thumb]

On Mon, Dec 19, 2011 at 05:09:11PM +0200, Heikki Linnakangas wrote:
> Actually, I believe our Itanium (and possibly ARM, too) implementation
> of S_UNLOCK() is wrong as it is. There is no platform-specific
> S_UNLOCK() defined for Itanium, so we're using the generic
> implementation:
>
> #if !defined(S_UNLOCK)
> #define S_UNLOCK(lock)        (*((volatile slock_t *) (lock)) = 0)
> #endif     /* S_UNLOCK */
>
> That is not sufficient on platforms with a weak memory model, like Itanium.

Other processors may observe the lock as held after its release, but there's no
correctness problem.