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

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 14/15] futex: convert futex_pi_state.refcount to refcount_t
Date	2017-09-01 21:20 +0200
Message-ID	<ukZDX-RU-3@gated-at.bofh.it> (permalink)
References	(5 earlier) <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>
Organization	linux.* mail to news gateway

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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

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