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Re: atomic accesses
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.