atomic accesses

[David Daney]

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.


David Daney