Re: different kind of memory reordering clarification

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Wed, Apr 11, 2018 at 10:46:28AM +0800, Yubin Ruan wrote:
> On Tue, Apr 10, 2018 at 10:04:09AM -0700, Paul E. McKenney wrote:
> > On Tue, Apr 10, 2018 at 11:20:24PM +0800, Yubin Ruan wrote:
> > > On Tue, Apr 10, 2018 at 08:14:08PM +0800, Yubin Ruan wrote:
> [...]
> > > > 
> > > > Can you please provide me with some examples or references for different kinds
> > > > of memory reordering in a SMP system? You know, there are different kinds of
> > > > reordering:
> > > > 
> > > >    - Loads reordered after loads
> > > >    - Loads reordered after stores
> > > >    - Stores reordered after stores
> > > >    - Stores reordered after loads
> > > >    - Atomic reordered with loads
> > > >    - Atomic reordered with stores
> > > >    - Dependent loads reordered (DEC alpha)
> > > 
> > > I remember there is open-std.org webpage containing comparision of C++'s
> > > memory model to those primitives used in the Linux kernel. But I just can't
> > > find that page.
> > 
> > Here you go!
> > 
> > http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0124r4.html
> > 
> > There will be an update in a month or so, but the above is pretty
> > close.  Also, the Linux-kernel memory model was presented at
> > ASPLOS and accepted into the Linux kernel itself:
> > 
> > https://paulmck.livejournal.com/49667.html
> 
> Many thanks. But I am currently confused about the relationship between
> terminologies used in the Linux kernel and those used in some programming
> languages (e.g., C++), i.e., the relationships between
> 
>     memory_order_release
>     memory_order_relaxed
>     memory_order_acquire
>     memory_order_seq_cst
>     ...
> 
> and those used in the kernel:
> 
>     READ_ONCE() / WRITE_ONCE()
>     rmb() / wmb() / mb() / smp_mb()
>     ...
> 
> Any materials for that?

The URL I posted above:

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0124r4.html

							Thanx, Paul