From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
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, dvhart@linux.intel.com,
fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com
Subject: Re: [PATCH v2 tip/core/rcu 03/11] rcu: Move smp_mb() from rcu_seq_snap() to rcu_exp_gp_seq_snap()
Date: Thu, 10 Dec 2015 12:41:21 -0800 [thread overview]
Message-ID: <20151210204121.GK28602@linux.vnet.ibm.com> (raw)
In-Reply-To: <20151210202939.GC6356@twins.programming.kicks-ass.net>
On Thu, Dec 10, 2015 at 09:29:39PM +0100, Peter Zijlstra wrote:
> On Wed, Dec 09, 2015 at 03:03:00PM -0800, Paul E. McKenney wrote:
> > The memory barrier in rcu_seq_snap() is needed only for grace periods,
> > so this commit moves it to the grace-period-oriented wrapper
> > rcu_exp_gp_seq_snap().
>
> This is a bit short for a memory barrier changelog. I think I remember
> enough of the code to see this is indeed so, but who knows who will
> remember what in another few weeks :-)
;-)
Would it help to add something like the following?
This change does not add or remove a memory barrier, but instead
associates it with the right level of abstraction.
Thanx, Paul
next prev parent reply other threads:[~2015-12-10 20:41 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-09 23:02 [PATCH v2 tip/core/rcu 0/11] Expedited-grace-period changes for 4.5 Paul E. McKenney
2015-12-09 23:02 ` [PATCH v2 tip/core/rcu 01/11] rcu: Short-circuit synchronize_sched_expedited() if only one CPU Paul E. McKenney
2015-12-09 23:02 ` [PATCH v2 tip/core/rcu 02/11] rcu: Clarify role of ->expmaskinitnext Paul E. McKenney
2015-12-09 23:03 ` [PATCH v2 tip/core/rcu 03/11] rcu: Move smp_mb() from rcu_seq_snap() to rcu_exp_gp_seq_snap() Paul E. McKenney
2015-12-10 20:29 ` Peter Zijlstra
2015-12-10 20:41 ` Paul E. McKenney [this message]
2015-12-09 23:03 ` [PATCH v2 tip/core/rcu 04/11] rcu: Invert sync_rcu_exp_select_cpus() "if" statement Paul E. McKenney
2015-12-09 23:03 ` [PATCH v2 tip/core/rcu 05/11] rcu: Reduce expedited GP memory contention via per-CPU variables Paul E. McKenney
2015-12-09 23:03 ` [PATCH v2 tip/core/rcu 06/11] rcu: Make expedited grace periods resolve stall-warning ties Paul E. McKenney
2015-12-09 23:03 ` [PATCH v2 tip/core/rcu 07/11] rcu: Add more diagnostics to expedited stall warning messages Paul E. McKenney
2015-12-09 23:03 ` [PATCH v2 tip/core/rcu 08/11] rcu: Add rcu_normal kernel parameter to suppress expediting Paul E. McKenney
2015-12-09 23:03 ` [PATCH v2 tip/core/rcu 09/11] rcu: Wire up rcu_end_inkernel_boot() Paul E. McKenney
2015-12-09 23:03 ` [PATCH v2 tip/core/rcu 10/11] rcu: Allow expedited grace periods to be disabled at init Paul E. McKenney
2015-12-09 23:03 ` [PATCH v2 tip/core/rcu 11/11] rcu: Remove TINY_RCU bloat from pointless boot parameters Paul E. McKenney
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