linux-kernel - Re: [PATCH 14/15] futex: convert futex_pi_state.refcount to refcount

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Message-ID: <20170901123415.s3fxlyeyourz47av@hirez.programming.kicks-ass.net>
Date:   Fri, 1 Sep 2017 14:34:15 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Reshetova, Elena" <elena.reshetova@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
        "tj@...nel.org" <tj@...nel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hannes@...xchg.org" <hannes@...xchg.org>,
        "lizefan@...wei.com" <lizefan@...wei.com>,
        "acme@...nel.org" <acme@...nel.org>,
        "alexander.shishkin@...ux.intel.com" 
        <alexander.shishkin@...ux.intel.com>,
        "eparis@...hat.com" <eparis@...hat.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "arnd@...db.de" <arnd@...db.de>,
        "luto@...nel.org" <luto@...nel.org>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "dvhart@...radead.org" <dvhart@...radead.org>,
        "ebiederm@...ssion.com" <ebiederm@...ssion.com>
Subject: Re: [PATCH 14/15] futex: convert futex_pi_state.refcount to
 refcount_t

On Fri, Sep 01, 2017 at 11:05:33AM +0000, Reshetova, Elena wrote:
> Actually on the second thought: does the above memory ordering differences
> really apply when  we have ARCH_HAS_REFCOUNT? To me it looks like the way
> how it is currently implemented for x86 is the same way as it is for atomic cases.

Never look to x86 for memory ordering, its boring.

And yes, for the ARM implementation it can certainly make a difference.