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Date: Tue, 17 Mar 2015 10:10:09 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        linux-kernel@vger.kernel.org,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Nicholas Miell <nmiell@comcast.net>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Ingo Molnar <mingo@redhat.com>, Alan Cox <gnomes@lxorguk.ukuu.org.uk>,
        Lai Jiangshan <laijs@cn.fujitsu.com>,
        Stephen Hemminger <stephen@networkplumber.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Josh Triplett <josh@joshtriplett.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        David Howells <dhowells@redhat.com>, Christoph Lameter <cl@linux.com>
Subject: Re: [RFC PATCH] sys_membarrier(): system/process-wide memory
 barrier (x86) (v12)
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On Tue, 17 Mar 2015 04:44:11 -0700
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote:

> On Tue, Mar 17, 2015 at 07:40:56AM +0100, Peter Zijlstra wrote:
> > On Mon, Mar 16, 2015 at 10:26:11PM -0400, Steven Rostedt wrote:
> > > As I recently found out that this_cpu_read/write() is not that nice on
> > > all architectures,
> > 
> > In fact, they only really work well on x86. Aargh64 seems to have a semi
> > usable version, but mostly its quite horrible indeed.
> 
> Yeah, if you are in a preempt-disabled region, __this_cpu_read() and
> __this_cpu_write() generate much better code on most platforms.
> 

I was just having this discussion with Christoph. I originally switched
to using this_cpu_ptr(), but I'll try __this_cpu* instead. I think
Christoph recommended that too.

-- Steve