Re: [PATCH 14/15] futex: convert futex_pi_state.refcount to refcount_t

Path	csiph.com!news.redatomik.org!aioe.org!bofh.it!news.nic.it!robomod
From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 14/15] futex: convert futex_pi_state.refcount to refcount_t
Date	Fri, 01 Sep 2017 21:20:01 +0200
Message-ID	<ukZDX-RU-3@gated-at.bofh.it> (permalink)
References	<ukai5-8hx-3@gated-at.bofh.it> <ukai7-8hx-49@gated-at.bofh.it> <ukOSd-Pw-5@gated-at.bofh.it> <ukQAG-21R-21@gated-at.bofh.it> <ukQKl-25K-1@gated-at.bofh.it> <ukRZL-3id-7@gated-at.bofh.it> <ukToS-4zk-3@gated-at.bofh.it> <ukUbg-5pL-47@gated-at.bofh.it> <ukUkX-5wR-53@gated-at.bofh.it> <ukXCa-81A-13@gated-at.bofh.it>
X-Original-To	"Reshetova, Elena" <elena.reshetova@intel.com>
Dkim-Signature	v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=BNgohbR0rJ7Rej0MgKz7pWFN0OzfqpfcRLfwXfkHP08=; b=uJUlIMBqSyf1ScKHn0Ww76DaD 17UGx6vTCWbnM4xOI5YPam44xuNOkMTYmyUQgP5ibr4xRhmx2RyR5Rbdx0RX9z3C2se4g0fH/nY/P cJZ8YblLcQUCveNtmAfBNITfnVF6F8yOjTzMq3vQ5OlywVTY/4HogwUaOTaSfLa0JDY363i64t5Ru Xhey3Pe+3RzwC+9yEFq734wY5w3Wn3EVQp7pSOl0aRsbE5pWEhYcWHeuYC2QV20pFSeN3URsdxbMB z9Kzn1CyCPIM2aQMdb0Tr6PmJTBMlg6mkmlQO+Wy3VdDVLzCBydnYx5W4sPt4CtDa0zb/JA2vrnfe dza7D28YA==;
MIME-Version	1.0
Content-Type	text/plain; charset=us-ascii
Content-Disposition	inline
User-Agent	NeoMutt/20170609 (1.8.3)
Sender	robomod@news.nic.it
List-ID	<linux-kernel.vger.kernel.org>
X-Mailing-List	linux-kernel@vger.kernel.org
Approved	robomod@news.nic.it
Lines	26
Organization	linux.* mail to news gateway
X-Original-Cc	Thomas Gleixner <tglx@linutronix.de>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>, "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>, "viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>, "tj@kernel.org" <tj@kernel.org>, "mingo@redhat.com" <mingo@redhat.com>, "hannes@cmpxchg.org" <hannes@cmpxchg.org>, "lizefan@huawei.com" <lizefan@huawei.com>, "acme@kernel.org" <acme@kernel.org>, "alexander.shishkin@linux.intel.com" <alexander.shishkin@linux.intel.com>, "eparis@redhat.com" <eparis@redhat.com>, "akpm@linux-foundation.org" <akpm@linux-foundation.org>, "arnd@arndb.de" <arnd@arndb.de>, "luto@kernel.org" <luto@kernel.org>, "keescook@chromium.org" <keescook@chromium.org>, "dvhart@infradead.org" <dvhart@infradead.org>, "ebiederm@xmission.com" <ebiederm@xmission.com>
X-Original-Date	Fri, 1 Sep 2017 21:12:34 +0200
X-Original-Message-ID	<20170901191234.ghybbmpm73miwmkp@hirez.programming.kicks-ass.net>
X-Original-References	<1504095773-22895-1-git-send-email-elena.reshetova@intel.com> <1504095773-22895-15-git-send-email-elena.reshetova@intel.com> <alpine.DEB.2.20.1709010939360.1857@nanos> <20170901093852.it4d4bxoy2lmojrk@hirez.programming.kicks-ass.net> <alpine.DEB.2.20.1709011142310.1857@nanos> <2236FBA76BA1254E88B949DDB74E612B6FF6347F@IRSMSX102.ger.corp.intel.com> <20170901123415.s3fxlyeyourz47av@hirez.programming.kicks-ass.net> <2236FBA76BA1254E88B949DDB74E612B6FF63506@IRSMSX102.ger.corp.intel.com> <20170901133644.jf57pwuaep6zirxz@hirez.programming.kicks-ass.net> <2236FBA76BA1254E88B949DDB74E612B6FF6369D@IRSMSX102.ger.corp.intel.com>
X-Original-Sender	linux-kernel-owner@vger.kernel.org
Xref	csiph.com linux.kernel:1725299

Show key headers only | View raw

On Fri, Sep 01, 2017 at 05:03:55PM +0000, Reshetova, Elena wrote:
> > On Fri, Sep 01, 2017 at 01:24:16PM +0000, Reshetova, Elena wrote:
> > >
> > > > 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.
> > >
> > > So, yes, what I am trying to say is that it can really depend if you have
> > ARCH_HAS_REFCOUNT
> > > enabled or not and then also based on architecture. Thus I believe is also true for
> > atomic: there
> > > might be differences when you use arch. dependent version of function or not.
> > 
> > So the generic one in lib/refcount.c is already weaker on ARM, they
> > don't need to do a ARCH specific 'fast' implementation for the
> > difference to show up.
> 
> But can they make "fast" implementation on ARM that would give stronger memory guarantees?

Whatever for?

Thread

[PATCH 00/15] v5 kernel core pieces refcount conversions Elena Reshetova <elena.reshetova@intel.com> - 2017-08-30 14:30 +0200
  [PATCH 05/15] sched/task_struct: convert task_struct.usage to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-08-30 14:30 +0200
  [PATCH 10/15] uprobes: convert uprobe.ref to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-08-30 14:30 +0200
  [PATCH 14/15] futex: convert futex_pi_state.refcount to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-08-30 14:30 +0200
    Re: [PATCH 14/15] futex: convert futex_pi_state.refcount to  refcount_t Thomas Gleixner <tglx@linutronix.de> - 2017-09-01 09:50 +0200
      Re: [PATCH 14/15] futex: convert futex_pi_state.refcount to  refcount_t Peter Zijlstra <peterz@infradead.org> - 2017-09-01 11:40 +0200
        Re: [PATCH 14/15] futex: convert futex_pi_state.refcount to  refcount_t Thomas Gleixner <tglx@linutronix.de> - 2017-09-01 11:50 +0200
          RE: [PATCH 14/15] futex: convert futex_pi_state.refcount to  refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-09-01 13:00 +0200
          RE: [PATCH 14/15] futex: convert futex_pi_state.refcount to  refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-09-01 13:10 +0200
            Re: [PATCH 14/15] futex: convert futex_pi_state.refcount to  refcount_t Peter Zijlstra <peterz@infradead.org> - 2017-09-01 14:40 +0200
              RE: [PATCH 14/15] futex: convert futex_pi_state.refcount to  refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-09-01 15:30 +0200
                Re: [PATCH 14/15] futex: convert futex_pi_state.refcount to  refcount_t Peter Zijlstra <peterz@infradead.org> - 2017-09-01 15:40 +0200
                RE: [PATCH 14/15] futex: convert futex_pi_state.refcount to  refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-09-01 19:10 +0200
                Re: [PATCH 14/15] futex: convert futex_pi_state.refcount to  refcount_t Peter Zijlstra <peterz@infradead.org> - 2017-09-01 21:20 +0200
                RE: [PATCH 14/15] futex: convert futex_pi_state.refcount to  refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-09-04 12:40 +0200
                Re: [PATCH 14/15] futex: convert futex_pi_state.refcount to  refcount_t Peter Zijlstra <peterz@infradead.org> - 2017-09-04 14:10 +0200
  [PATCH 07/15] perf: convert perf_event_context.refcount to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-08-30 14:30 +0200
  [PATCH 03/15] sched: convert user_struct.__count to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-08-30 14:30 +0200
  [PATCH 11/15] nsproxy: convert nsproxy.count to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-08-30 14:30 +0200
  Re: [PATCH 00/15] v5 kernel core pieces refcount conversions Kees Cook <keescook@chromium.org> - 2017-09-01 01:50 +0200
    Re: [PATCH 00/15] v5 kernel core pieces refcount conversions Peter Zijlstra <peterz@infradead.org> - 2017-09-01 11:50 +0200
      Re: [PATCH 00/15] v5 kernel core pieces refcount conversions Kees Cook <keescook@chromium.org> - 2017-09-01 19:00 +0200
        RE: [PATCH 00/15] v5 kernel core pieces refcount conversions "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-09-01 19:10 +0200

csiph-web