linux-kernel - Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option

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:   Thu, 27 Jul 2017 05:56:59 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, mingo@...nel.org,
        jiangshanlai@...il.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, fweisbec@...il.com,
        oleg@...hat.com
Subject: Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option

On Thu, Jul 27, 2017 at 12:14:26PM +0200, Peter Zijlstra wrote:
> On Tue, Jul 25, 2017 at 12:36:12PM -0700, Paul E. McKenney wrote:
> > This horse is already out, so trying to shut the gate won't be effective.
> 
> So I'm not convinced it is. The mprotect() hack isn't portable as we've
> established and on x86 where it does work, it doesn't (much) perturb
> tasks not related to our process because we keep a tight mm_cpumask().

Wrong.  People are using it today, portable or not.  If we want them
to stop using it, we need to give them an alternative.  Period.

> And if there are other (unpriv.) means of spraying IPIs around, we
> should most certainly look at fixing those, not just shrug and make
> matters worse.

We need to keep an open mind for a bit.  If there was a trivial
solution, we would have implemented it back in 2010.

							Thanx, Paul