atomic accesses

[Richard Guenther]

On Tue, Mar 4, 2008 at 7:31 PM, David Daney <ddaney@avtrex.com> wrote:
> Jakub Jelinek wrote:
>  > On Tue, Mar 04, 2008 at 04:37:29PM +0000, Andrew Haley wrote:
>  >>> Typically those would be found in asm statements.
>  >>> I suspect it would be valuable to have standardized primitives for
>  >>> atomic actions (semaphores, spinlocks, test-and-set primitives,
>  >>> circular buffers, pick one).
>  >> We already have these in gcc, and they're even documented.
>  >
>  > We don't have atomic read or atomic write builtins (ok, you could
>  > abuse __sync_fetch_and_add (&x, 0) for atomic read and a loop
>  > with __sync_compare_and_swap_val for atomic store, but that's a horrible
>  > overkill.
>
>  There is nothing preventing us from adding __sync_fetch and __sync_store
>  so that we could avoid the overkill.
>
>  Perhaps anything declared volatile should have these semantics.
>  Although mentioning 'volatile' on the lkml is probably not a good idea.

Certainly not.  volatile has nothing to do with atomic access.

Richard.