linux-kernel - Re: [PATCH tip/core/rcu 01/14] rcu: Protect rcu_boost() lockless accesses with ACCESS

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 9 Jan 2015 06:07:34 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Davidlohr Bueso <dave@...olabs.net>, linux-kernel@...r.kernel.org,
	mingo@...nel.org, laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	josh@...htriplett.org, tglx@...utronix.de, rostedt@...dmis.org,
	dhowells@...hat.com, edumazet@...gle.com, dvhart@...ux.intel.com,
	fweisbec@...il.com, oleg@...hat.com, bobby.prani@...il.com,
	borntraeger@...ibm.com
Subject: Re: [PATCH tip/core/rcu 01/14] rcu: Protect rcu_boost() lockless
 accesses with ACCESS_ONCE()

On Fri, Jan 09, 2015 at 02:56:14PM +0100, Peter Zijlstra wrote:
> On Fri, Jan 09, 2015 at 05:49:54AM -0800, Paul E. McKenney wrote:
> > > That reminds me, I think the new conversion for stores will most likely
> > > introduce silly arg bugs:
> > > 
> > > -       ACCESS_ONCE(a) = b;
> > > +       ASSIGN_ONCE(b, a);
> > 
> > I was planning to do mine by hand for this sort of reason.
> > 
> > Or are you thinking of something more subtle than the case where
> > "b" is an unparenthesized comma-separated expression?
> 
> I think he's revering to the wrong way around-ness of the thing.
> 
> Its a bit of a mixed bag on assignments, but for instance
> rcu_assign_pointer() takes them the right way around, as does
> atomic_set().
> 
> So yes, I think the ASSIGN_ONCE() thing got the arguments the wrong way
> around.

Ah, yes, I had forgotten about this point.

> We could maybe still change it, before its in too long ?

I would be in favor.  Any objections?  ;-)

							Thanx, Paul

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/