Message-ID: <1377830702.4028.50.camel@pasglop>
Subject: Re: [PATCH v7 1/4] spinlock: A new lockref structure for lockless
 update of refcount
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Neuling <mikey@neuling.org>, Ingo Molnar <mingo@kernel.org>,
        Waiman Long <Waiman.Long@hp.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Jeff Layton <jlayton@redhat.com>, Miklos Szeredi <mszeredi@suse.cz>,
        Ingo Molnar <mingo@redhat.com>, Thomas Gleixner <tglx@linutronix.de>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Steven Rostedt <rostedt@goodmis.org>, Andi Kleen <andi@firstfloor.org>,
        "Chandramouleeswaran, Aswin" <aswin@hp.com>,
        "Norton, Scott J" <scott.norton@hp.com>
Date: Fri, 30 Aug 2013 12:45:02 +1000
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On Thu, 2013-08-29 at 19:35 -0700, Linus Torvalds wrote:
> That said, on power, you have that "ACCESS_ONCE()" implicit in the
> *type*, not in the code, so an "arch_spinlock_t" is fundamentally
> volatile in itself. It's one of the reasons I despise "volatile":
> things like volatility are _not_ attributes of a variable or a type,
> but of the code in question. Something can be volatile in one context,
> but not in another (one context might be locked, for example).

Right, we can probably change that to use ACCESS_ONCE... volatile tend
to never quite do what you expect anyway.

Cheers,
Ben.


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