Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to refcount_t

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to refcount_t
Date	2017-03-22 13:30 +0100
Message-ID	<tnNyO-2kr-7@gated-at.bofh.it> (permalink)
References	(5 earlier) <tn5R7-5oQ-5@gated-at.bofh.it> <tnyT8-8vM-7@gated-at.bofh.it> <tnzvQ-BH-3@gated-at.bofh.it> <tnBR0-266-33@gated-at.bofh.it> <tnDSN-3DX-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Tue, Mar 21, 2017 at 07:03:19PM -0700, Eric Dumazet wrote:

> Note that we might define two refcount_inc()  : One that does whole
> tests, and refcount_inc_relaxed() that might translate to atomic_inc()
> on non debug kernels.

So you'd want a duplicate interface, such that most code, which doesn't
care about refcount performance much, can still have all the tests
enabled.

But the code that cares about it (and preferably can prove it with
numbers) can use the other.

I'm also somewhat hesitant to use _relaxed for this distinction, as it
has a clear meaning in atomics, maybe _nocheck?

Also; what operations do you want _nocheck variants of, only
refcount_inc() ?

That said; I'm really loath to provide these without actual measurements
that prove they make a difference.

> Then later, maybe provide a dynamic infrastructure so that we can
> dynamically force the full checks even for refcount_inc_relaxed() on say
> 1% of the hosts, to get better debug coverage ?

Shouldn't be too hard to do in arch specific code using alternative
stuff. Generic code could use jump labels I suppose, but that would
result in bigger code.

Thread

[PATCH 00/17] net subsystem refcount conversions Elena Reshetova <elena.reshetova@intel.com> - 2017-03-16 16:30 +0100
  [PATCH 02/17] net: convert neigh_params.refcnt from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-03-16 16:30 +0100
  [PATCH 10/17] net: convert in_device.refcnt from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-03-16 16:40 +0100
  [PATCH 12/17] net: convert unix_address.refcnt from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-03-16 16:40 +0100
  [PATCH 14/17] net: convert inet_frag_queue.refcnt from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-03-16 16:40 +0100
  [PATCH 01/17] net: convert neighbour.refcnt from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-03-16 16:40 +0100
  [PATCH 11/17] net: convert netpoll_info.refcnt from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-03-16 16:40 +0100
  [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-03-16 16:40 +0100
    Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Eric Dumazet <eric.dumazet@gmail.com> - 2017-03-16 18:00 +0100
      Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to refcount_t Kees Cook <keescook@chromium.org> - 2017-03-16 18:40 +0100
        Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t David Miller <davem@davemloft.net> - 2017-03-16 20:20 +0100
          RE: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-03-17 08:50 +0100
            Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Eric Dumazet <eric.dumazet@gmail.com> - 2017-03-17 17:20 +0100
              Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Herbert Xu <herbert@gondor.apana.org.au> - 2017-03-18 18:00 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t David Miller <davem@davemloft.net> - 2017-03-19 02:40 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Peter Zijlstra <peterz@infradead.org> - 2017-03-20 11:50 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Peter Zijlstra <peterz@infradead.org> - 2017-03-20 14:30 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Peter Zijlstra <peterz@infradead.org> - 2017-03-20 14:50 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Eric Dumazet <eric.dumazet@gmail.com> - 2017-03-20 16:00 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Eric Dumazet <eric.dumazet@gmail.com> - 2017-03-20 17:20 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Eric Dumazet <eric.dumazet@gmail.com> - 2017-03-20 17:40 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Eric Dumazet <eric.dumazet@gmail.com> - 2017-03-20 16:30 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Peter Zijlstra <peterz@infradead.org> - 2017-03-20 16:50 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to refcount_t Kees Cook <keescook@chromium.org> - 2017-03-21 21:50 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Eric Dumazet <eric.dumazet@gmail.com> - 2017-03-21 22:30 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t David Miller <davem@davemloft.net> - 2017-03-21 23:40 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to refcount_t Kees Cook <keescook@chromium.org> - 2017-03-22 01:00 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Eric Dumazet <eric.dumazet@gmail.com> - 2017-03-22 03:10 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Peter Zijlstra <peterz@infradead.org> - 2017-03-22 13:30 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Eric Dumazet <eric.dumazet@gmail.com> - 2017-03-22 14:30 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Peter Zijlstra <peterz@infradead.org> - 2017-03-22 15:40 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Eric Dumazet <eric.dumazet@gmail.com> - 2017-03-22 16:00 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Peter Zijlstra <peterz@infradead.org> - 2017-03-22 16:10 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Eric Dumazet <eric.dumazet@gmail.com> - 2017-03-22 16:30 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Peter Zijlstra <peterz@infradead.org> - 2017-03-22 18:00 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to refcount_t Kees Cook <keescook@chromium.org> - 2017-03-22 20:10 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Peter Zijlstra <peterz@infradead.org> - 2017-03-22 14:50 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Herbert Xu <herbert@gondor.apana.org.au> - 2017-03-20 15:50 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Herbert Xu <herbert@gondor.apana.org.au> - 2017-03-20 14:50 +0100
                RE: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t David Laight <David.Laight@ACULAB.COM> - 2017-03-20 15:20 +0100
                Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t Peter Zijlstra <peterz@infradead.org> - 2017-03-20 15:30 +0100
                RE: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to  refcount_t David Laight <David.Laight@ACULAB.COM> - 2017-03-20 16:10 +0100
  [PATCH 05/17] net: convert sk_buff_fclones.fclone_ref from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-03-16 16:40 +0100
  [PATCH 15/17] net: convert net.passive from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-03-16 16:40 +0100
  [PATCH 16/17] net: convert netlbl_lsm_cache.refcount from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-03-16 16:40 +0100
  [PATCH 09/17] net: convert ip_mc_list.refcnt from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-03-16 16:40 +0100
  [PATCH 04/17] net: convert sk_buff.users from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-03-16 16:40 +0100
  [PATCH 08/17] net: convert sk_filter.refcnt from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-03-16 16:40 +0100
    Re: [PATCH 08/17] net: convert sk_filter.refcnt from atomic_t to  refcount_t Daniel Borkmann <daniel@iogearbox.net> - 2017-03-16 17:10 +0100
      RE: [PATCH 08/17] net: convert sk_filter.refcnt from atomic_t to  refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-03-17 09:20 +0100
  [PATCH 17/17] net: convert packet_fanout.sk_ref from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-03-16 16:40 +0100
  [PATCH 06/17] net: convert sock.sk_wmem_alloc from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-03-16 16:40 +0100
  [PATCH 13/17] net: convert fib_rule.refcnt from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-03-16 16:40 +0100

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