Re: [RFC PATCH 3/4] hp: Implement Hazard Pointers

[Mathieu Desnoyers]

On 2024-10-07 15:47, Boqun Feng wrote:
> On Thu, Oct 03, 2024 at 09:30:53AM -0400, Mathieu Desnoyers wrote:
> [...]
> > > > +	/*
> > > > +	 * Use RCU dereference without lockdep checks, because
> > > > +	 * lockdep is not aware of HP guarantees.
> > > > +	 */
> > > > +	addr2 = rcu_access_pointer(*addr_p);	/* Load A */
> > >
> > > Why rcu_access_pointer() instead of READ_ONCE()? Because you want to
> > > mark the head of address dependency?
> >
> > Yes, the intent here is to mark the address dependency and provide
> > a publication guarantee similar to RCU pairing rcu_assign_pointer
> > and rcu_dereference. Do you see any reason why READ_ONCE() would
> > suffice here ?
>
> READ_ONCE() also provides address dependencies. See the "DEPENDENCY
> RELATIONS: data, addr, and ctrl" section in
> tools/memory-model/Documentation/explanantion.txt.

Fair point, so let's use READ_ONCE() then.

Thanks,

Mathieu

> Regards,
> Boqun
>
> > Thanks,
> >
> > Mathieu

--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com