On Wed, Oct 18, 2017 at 05:18:37PM -0400, Alan Stern wrote:
> On Wed, 18 Oct 2017, Paul E. McKenney wrote:
>
> > > Well, you could explicitly mention that in the multi-thread case, this
> > > means all accesses to the shared variable had better use READ_ONCE() or
> > > WRITE_ONCE().
> >
> > Like this?
> >
> > Thanx, Paul
> >
> > ------------------------------------------------------------------------
> >
> > d. If there are multiple CPUs, accesses to shared variables
> > should use READ_ONCE() and WRITE_ONCE() or stronger
> > to prevent load/store tearing, load/store fusing, and
> > invented loads and stores. There are exceptions to
> > this rule, for example:
> >
> > i. When there is no possibility of a given
> > shared variable being updated, for example,
> > while holding the update-side lock, reads
> > from that variable need not use READ_ONCE().
> >
> > ii. When there is no possibility of a given shared
> > variable being either read or updated, for
> > example, when running during early boot, reads
> > from that variable need not use READ_ONCE() and
> > writes to that variable need not use WRITE_ONCE().
>
> Yeah, except that you mean being read or updated by another thread.
Good point, added that qualifier.
Thanx, Paul
