linux-kernel - Re: [RFC PATCH] sys_membarrier(): system/process-wide memory barrier (x86) (v12)

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] [day] [month] [year] [list]

Message-ID: <20150317210635.5d08255c@grimm.local.home>
Date:	Tue, 17 Mar 2015 21:06:35 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Nicholas Miell <nmiell@...cast.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>,
	Alan Cox <gnomes@...rguk.ukuu.org.uk>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Stephen Hemminger <stephen@...workplumber.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Josh Triplett <josh@...htriplett.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	David Howells <dhowells@...hat.com>
Subject: Re: [RFC PATCH] sys_membarrier(): system/process-wide memory
 barrier (x86) (v12)

On Tue, 17 Mar 2015 12:46:41 +0000 (UTC)
Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:


> > Would that help?
> > 
> > 	this_cpu_write(saved_next, next);
> > 	rq = context_switch(rq, prev, next);
> > 	rq->curr = this_cpu_read(saved_next);
> 
> Assuming there is a full memory barrier (e.g. load_cr3) within
> context_switch, it would help for ordering memory accesses that
> are performed prior to the preemption, but not for memory accesses
> to be performed immediately after return to userspace from preemption.

Hmm, I was thinking that there was a spin_unlock(rq->lock) after that,
but it appears that context_switch() does the unlock. If there was an
spin_unlock() after this code, then it could work. There's always
setting the rq->curr in the context_switch() call itself.

-- Steve
--
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/