Re: Portable memory barrier?

[Jere <jhb.chat@gmail.com>]

On Thursday, May 11, 2017 at 3:36:09 AM UTC-4, Dmitry A. Kazakov wrote:
> On 11/05/2017 00:56, Jere wrote:
> > On Wednesday, May 10, 2017 at 1:26:00 AM UTC-4, J-P. Rosen wrote:
> >> Le 10/05/2017 à 02:51, Jere a écrit :
> >>> Is there a method besides Atomic?  If I am implementing a generic FIFO (lock
> >>> free) and the FIFO elements are complex data types that may not be able to be
> >>> atomic, do I have any other options or are protected objects my only way out?
> >>
> >> Protected objects, or for a lower level, Synchronous_Task_Control. I
> >> know that you want lock free algorithms, but out of curiosity, did you
> >> measure the cost of locking algorithms? IOW, is all of this worth the
> >> trouble?
> 
> > I wasn't necessarily aiming for a specific speed/cost.  I know I can easily
> > find a standard task safe container and use that and it might be faster (or at
> > least fast enough) on various platforms.  This is more for a different option
> > from the normal.  It might be faster on some platforms or slower, but it is
> > mostly meant to be a tool in toolkit.
>
> <SNIPPED>
> 
> So, Jere, when you become ARG (:-)), please, push for requirement to 
> support Atomic for all scalar objects. If the machine lacks 
> corresponding instructions the compiler must fall back to a protected 
> object. And conversely, if there is a strong case that using a protected 
> action might be more efficient than machine's atomic access 
> instructions, the compiler should use the former.
> 

Well,I believe Randy was offering up to Shark8, but it is definitely the type of 
thing I enjoy.  I'm very much into semantics when it comes to this type of 
stuff, though obviously I am no where near good enough in the Ada standard.  Nor 
am I experienced enough yet with enough big systems.  My experience is mainly in 
bare metal applications, where Ada is not very predominant (though not absent).  
I am much more comfortable in areas where there are no OS'es and the CPU's are 
fairly simple microcontrollers (8 to 32bit single core). 

I read through a lot of the posted ARG discussions/minutes, and I did find them 
pretty interesting.  I found myself disagreeing with some people and agreeing 
with others.  That said, I am very inexperienced and backseat ARG'ing is easy to 
do when I am in my position.  It's a difficult job I am sure!