linux-kernel - Re: [GIT PULL] ring-buffer: Replace this_cpu_*() with __this_cpu

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]

Message-ID: <20150519114201.39c19d61@gandalf.local.home>
Date:	Tue, 19 May 2015 11:42:01 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	stable <stable@...r.kernel.org>,
	Uwe Kleine-Koenig <u.kleine-koenig@...gutronix.de>
Subject: Re: [GIT PULL] ring-buffer: Replace this_cpu_*() with
 __this_cpu_*()

On Tue, 19 May 2015 10:35:32 -0500 (CDT)
Christoph Lameter <cl@...ux.com> wrote:

> On Thu, 19 Mar 2015, Steven Rostedt wrote:
> 
> > On Thu, 19 Mar 2015 15:16:25 -0700
> > Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> >
> > > So I don't think the ring-buffer change is necessarily _wrong_, but if
> > > this is a performance issue, why don't we just fix it up for the
> > > generic case rather than for just one user?
> >
> > I totally agree with your analysis, but it's up to Christoph to come up
> > with an answer to your questions.
> 
> Something beyond: Do not use this_cpu_* when preemption is already
> off but use __this_cpu_*?

I think the question was, why exactly does the generic this_cpu_read()
require disabling preemption? What breaks if it is not disabled?

-- 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/