Re: Litmus test for question from Al Viro

[Alan Stern]

On Mon, Oct 05, 2020 at 04:13:13PM +0100, Will Deacon wrote:
> > The failure to recognize the dependency in P0 should be considered a 
> > combined limitation of the memory model and herd7.  It's not a simple 
> > mistake that can be fixed by a small rewrite of herd7; rather it's a 
> > deliberate choice we made based on herd7's inherent design.  We 
> > explicitly said that control dependencies extend only to the code in the 
> > branches of an "if" statement; anything beyond the end of the statement 
> > is not considered to be dependent.
> 
> Interesting. How does this interact with loops that are conditionally broken
> out of, e.g.  a relaxed cmpxchg() loop or an smp_cond_load_relaxed() call
> prior to a WRITE_ONCE()?

Heh --  We finesse this issue by not supporting loops at all!  :-)

Alan