linux-kernel - Re: [PATCH 3/3] early_printk: Add simple serialization to early

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Message-Id: <20171004153829.GJ3521@linux.vnet.ibm.com>
Date:   Wed, 4 Oct 2017 08:38:29 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>, pmladek@...e.com,
        sergey.senozhatsky@...il.com, linux-kernel@...r.kernel.org,
        mingo@...nel.org, tglx@...utronix.de
Subject: Re: [PATCH 3/3] early_printk: Add simple serialization to
 early_vprintk()

On Wed, Oct 04, 2017 at 05:24:23PM +0200, Peter Zijlstra wrote:
> On Wed, Oct 04, 2017 at 07:17:45AM -0700, Paul E. McKenney wrote:
> > If you use READ_ONCE(), then all architectures I know of enforce
> > full ordering for accesses to a single variable.  (If you don't use
> > READ_ONCE(), then in theory Itanium can reorder reads.)  Me, I would
> > argue for WRITE_ONCE() as well to prevent store tearing.
> 
> Note that the stores are either cmpxchg() or smp_store_release() both of
> which imply a WRITE_ONCE().

That works for me!  ;-)

							Thanx, Paul