Re: [PATCH] list: Prevent compiler reloads inside 'safe' list iteration

[Paul E. McKenney]

On Tue, Mar 10, 2020 at 03:05:57PM +0000, David Laight wrote:
> From: Marco Elver
> > Sent: 10 March 2020 14:10
> ...
> > FWIW, for writes we're already being quite generous, in that plain
> > aligned writes up to word-size are assumed to be "atomic" with the
> > default (conservative) config, i.e. marking such writes is optional.
> > Although, that's a generous assumption that is not always guaranteed
> > to hold (https://lore.kernel.org/lkml/20190821103200.kpufwtviqhpbuv2n@willie-the-truck/).
> 
> Remind me to start writing everything in assembler.

Been there, done that.  :-/

> That and to mark all structure members 'volatile'.

Indeed.  READ_ONCE() and WRITE_ONCE() get this same effect, but without
pessimizing non-concurrent accesses to those same members.  Plus KCSAN
knows about READ_ONCE(), WRITE_ONCE(), and also volatile members.

							Thanx, Paul