linux-kernel - Re: [RFC PATCH 0/3] restartable sequences: fast user-space percpu critical sections

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:	Wed, 24 Jun 2015 17:07:28 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Paul Turner <pjt@...gle.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Andrew Hunter <ahh@...gle.com>,
	Andi Kleen <andi@...stfloor.org>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Linux API <linux-api@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Josh Triplett <josh@...htriplett.org>,
	Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Chris Lameter <cl@...ux.com>
Subject: Re: [RFC PATCH 0/3] restartable sequences: fast user-space percpu
 critical sections

On Wed, Jun 24, 2015 at 3:26 PM, Paul Turner <pjt@...gle.com> wrote:
> This is a fairly small series demonstrating a feature we've found to be quite
> powerful in practice, "restartable sequences".
>

On an extremely short glance, I'm starting to think that the right
approach, at least for x86, is to implement per-cpu gsbase.  Then you
could do cmpxchg with a gs prefix to atomically take a percpu lock and
atomically release a percpu lock and check whether someone else stole
the lock from you.  (Note: cmpxchg, unlike lock cmpxchg, is very
fast.)

This is totally useless for other architectures, but I think it would
be reasonable clean on x86.  Thoughts?

I can elaborate if necessary.

--Andy
--
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/