From: Peter Zijlstra <peterz@infradead.org>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
jiangshanlai@gmail.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, rostedt@goodmis.org,
dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com,
oleg@redhat.com, bobby.prani@gmail.com, dvyukov@google.com,
will.deacon@arm.com
Subject: Re: [PATCH tip/core/rcu 07/13] rcu: Add smp_mb__after_atomic() to sync_exp_work_done()
Date: Thu, 13 Apr 2017 18:24:09 +0200 [thread overview]
Message-ID: <20170413162409.q5gsqfytjyirgfep@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20170413161042.GA3956@linux.vnet.ibm.com>
On Thu, Apr 13, 2017 at 09:10:42AM -0700, Paul E. McKenney wrote:
> On Thu, Apr 13, 2017 at 11:18:32AM +0200, Peter Zijlstra wrote:
> > On Wed, Apr 12, 2017 at 09:55:43AM -0700, Paul E. McKenney wrote:
> > > However, a little future-proofing is a good thing,
> > > especially given that smp_mb__before_atomic() is only required to
> > > provide acquire semantics rather than full ordering. This commit
> > > therefore adds smp_mb__after_atomic() after the atomic_long_inc()
> > > in sync_exp_work_done().
> >
> > Oh!? As far as I'm away the smp_mb__{before,after}_atomic() really must
> > provide full MB, no confusion about that.
> >
> > We have other primitives for acquire/release.
>
> Hmmm... Rechecking atomic_ops.txt, it does appear that you are quite
> correct. Adding Will and Dmitry on CC, but dropping this patch for now.
I'm afraid that document is woefully out dated. I'm surprised it says
anything on the subject.
next prev parent reply other threads:[~2017-04-13 16:24 UTC|newest]
Thread overview: 106+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-12 16:54 [PATCH tip/core/rcu 0/13] Miscellaneous fixes for 4.12 Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 01/13] mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU Paul E. McKenney
2017-04-13 9:12 ` Peter Zijlstra
2017-04-13 11:06 ` Vlastimil Babka
2017-04-13 16:00 ` Paul E. McKenney
2017-04-13 16:17 ` Peter Zijlstra
2017-04-13 17:24 ` Paul E. McKenney
2017-04-13 21:30 ` Eric Dumazet
2017-04-14 8:45 ` Peter Zijlstra
2017-04-14 13:39 ` Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 02/13] lockdep: Use "WARNING" tag on lockdep splats Paul E. McKenney
2017-04-13 9:14 ` Peter Zijlstra
2017-04-13 16:01 ` Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 03/13] types: Update obsolete callback_head comment Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 04/13] rcu: Make RCU_FANOUT_LEAF help text more explicit about skew_tick Paul E. McKenney
2017-04-13 9:15 ` Peter Zijlstra
2017-04-13 16:03 ` Paul E. McKenney
2017-04-13 16:19 ` Peter Zijlstra
2017-04-13 16:55 ` Paul E. McKenney
2017-04-13 17:04 ` Peter Zijlstra
2017-04-13 17:31 ` Paul E. McKenney
2017-04-13 17:46 ` Peter Zijlstra
2017-04-13 18:19 ` Paul E. McKenney
2017-04-13 18:23 ` Peter Zijlstra
2017-04-13 18:42 ` Paul E. McKenney
2017-04-19 13:22 ` Peter Zijlstra
2017-04-19 13:48 ` Peter Zijlstra
2017-04-19 15:08 ` Paul E. McKenney
2017-04-19 15:40 ` Peter Zijlstra
2017-04-19 16:13 ` Paul E. McKenney
2017-04-19 14:50 ` Paul E. McKenney
2017-04-13 18:29 ` Peter Zijlstra
2017-04-13 19:42 ` Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 05/13] rcu: Remove obsolete comment from rcu_future_gp_cleanup() header Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 06/13] hlist_add_tail_rcu disable sparse warning Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 07/13] rcu: Add smp_mb__after_atomic() to sync_exp_work_done() Paul E. McKenney
2017-04-13 9:18 ` Peter Zijlstra
2017-04-13 9:33 ` Peter Zijlstra
2017-04-13 16:10 ` Paul E. McKenney
2017-04-13 16:24 ` Peter Zijlstra [this message]
2017-04-13 16:57 ` Paul E. McKenney
2017-04-13 17:10 ` Peter Zijlstra
2017-04-13 17:39 ` Paul E. McKenney
2017-04-13 17:51 ` Peter Zijlstra
2017-04-13 17:59 ` Peter Zijlstra
2017-04-19 23:24 ` Paul E. McKenney
2017-04-19 23:23 ` Paul E. McKenney
2017-04-20 11:17 ` Peter Zijlstra
2017-04-20 15:03 ` Paul E. McKenney
2017-04-20 15:08 ` Peter Zijlstra
2017-06-09 22:56 ` Paul E. McKenney
2017-06-12 14:51 ` Dmitry Vyukov
2017-06-12 21:54 ` Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 08/13] rcu: Improve comments for hotplug/suspend/hibernate functions Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 09/13] mm: Use static initialization for "srcu" Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 10/13] torture: Use correct path for Kconfig fragment for duplicates Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 11/13] rcu: Use bool value directly Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 12/13] rcu: Use true/false in assignment to bool Paul E. McKenney
2017-04-12 16:55 ` [PATCH tip/core/rcu 13/13] rcu: Fix typo in PER_RCU_NODE_PERIOD header comment Paul E. McKenney
2017-04-17 23:27 ` [PATCH v2 tip/core/rcu 0/13] Miscellaneous fixes for 4.12 Paul E. McKenney
2017-04-17 23:28 ` [PATCH v2 tip/core/rcu 01/11] mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU Paul E. McKenney
2017-04-18 0:14 ` David Rientjes
2017-04-17 23:28 ` [PATCH v2 tip/core/rcu 02/11] lockdep: Use "WARNING" tag on lockdep splats Paul E. McKenney
2017-04-19 15:00 ` Josh Triplett
2017-04-19 16:26 ` Paul E. McKenney
2017-04-17 23:28 ` [PATCH v2 tip/core/rcu 03/11] types: Update obsolete callback_head comment Paul E. McKenney
2017-04-17 23:28 ` [PATCH v2 tip/core/rcu 04/11] rcu: Make RCU_FANOUT_LEAF help text more explicit about skew_tick Paul E. McKenney
2017-04-18 0:18 ` Josh Triplett
2017-04-18 18:42 ` Paul E. McKenney
2017-04-17 23:28 ` [PATCH v2 tip/core/rcu 05/11] rcu: Remove obsolete comment from rcu_future_gp_cleanup() header Paul E. McKenney
2017-04-17 23:28 ` [PATCH v2 tip/core/rcu 06/11] hlist_add_tail_rcu disable sparse warning Paul E. McKenney
2017-04-17 23:28 ` [PATCH v2 tip/core/rcu 07/11] rcu: Improve comments for hotplug/suspend/hibernate functions Paul E. McKenney
2017-04-17 23:28 ` [PATCH v2 tip/core/rcu 08/11] torture: Use correct path for Kconfig fragment for duplicates Paul E. McKenney
2017-04-17 23:28 ` [PATCH v2 tip/core/rcu 09/11] rcu: Use bool value directly Paul E. McKenney
2017-04-17 23:28 ` [PATCH v2 tip/core/rcu 10/11] rcu: Use true/false in assignment to bool Paul E. McKenney
2017-04-17 23:28 ` [PATCH v2 tip/core/rcu 11/11] rcu: Fix typo in PER_RCU_NODE_PERIOD header comment Paul E. McKenney
2017-04-19 11:28 ` [PATCH v2 tip/core/rcu 0/13] Miscellaneous fixes for 4.12 Peter Zijlstra
2017-04-19 11:35 ` Peter Zijlstra
2017-04-19 11:48 ` Christian Borntraeger
2017-04-19 12:08 ` Peter Zijlstra
2017-04-19 12:51 ` Marc Zyngier
2017-04-19 14:47 ` Paul E. McKenney
2017-04-19 14:52 ` Peter Zijlstra
2017-04-19 15:13 ` Paul E. McKenney
2017-04-19 14:58 ` Josh Triplett
2017-04-19 15:03 ` Peter Zijlstra
2017-04-19 15:17 ` Paul E. McKenney
2017-04-19 13:22 ` Paul E. McKenney
2017-04-19 13:25 ` Christian Borntraeger
2017-04-19 13:02 ` Paul E. McKenney
2017-04-19 13:15 ` Peter Zijlstra
2017-04-19 15:37 ` Paul E. McKenney
2017-04-19 15:43 ` Peter Zijlstra
2017-04-19 16:12 ` Paul E. McKenney
2017-04-19 16:45 ` Paul E. McKenney
2017-04-19 16:46 ` [PATCH v3 tip/core/rcu 01/11] mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU Paul E. McKenney
2017-04-19 16:46 ` [PATCH v3 tip/core/rcu 02/11] lockdep: Use "WARNING" tag on lockdep splats Paul E. McKenney
2017-04-19 16:46 ` [PATCH v3 tip/core/rcu 03/11] types: Update obsolete callback_head comment Paul E. McKenney
2017-04-19 16:46 ` [PATCH v3 tip/core/rcu 04/11] rcu: Make RCU_FANOUT_LEAF help text more explicit about skew_tick Paul E. McKenney
2017-04-19 16:46 ` [PATCH v3 tip/core/rcu 05/11] rcu: Remove obsolete comment from rcu_future_gp_cleanup() header Paul E. McKenney
2017-04-19 16:46 ` [PATCH v3 tip/core/rcu 06/11] hlist_add_tail_rcu disable sparse warning Paul E. McKenney
2017-04-19 16:46 ` [PATCH v3 tip/core/rcu 07/11] rcu: Improve comments for hotplug/suspend/hibernate functions Paul E. McKenney
2017-04-19 16:46 ` [PATCH v3 tip/core/rcu 08/11] torture: Use correct path for Kconfig fragment for duplicates Paul E. McKenney
2017-04-19 16:46 ` [PATCH v3 tip/core/rcu 09/11] rcu: Use bool value directly Paul E. McKenney
2017-04-19 16:46 ` [PATCH v3 tip/core/rcu 10/11] rcu: Use true/false in assignment to bool Paul E. McKenney
2017-04-19 16:46 ` [PATCH v3 tip/core/rcu 11/11] rcu: Fix typo in PER_RCU_NODE_PERIOD header comment Paul E. McKenney
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