Re: [PATCH 11/18] seqcount: Introduce raw_write_seqcount_barrier()

Peter Zijlstra
2015-06-17T16:58:20Z

On Wed, Jun 17, 2015 at 08:42:45AM -0700, Paul E. McKenney wrote:
> > I would very much prefer a compiler switch that instructs the compiler
> > to not do bloody stupid things like this instead of marking every other
> > load/store in the kernel with volatile.
>
> I would of course be good with such a compiler switch, though my earlier
> attempts to negotiate one were unsuccessful. But I don't believe that we
> discussed a switch to specifically prohibit only use of to-be-stored-into
> variables as temporary scratch space. The trick is finding restrictions
> that are useful, but that don't imply -O0.

I would request on that disables all the 'stores from thin air'
'optimizations'. IOW assume everything is shared memory and concurrent
unless you can prove its not so. For example a local stack variable that
does not escape scope.