From: "Paul E. McKenney" <paulmck@linux•vnet.ibm.com>
To: "Michael S. Tsirkin" <mst@redhat•com>
Cc: Peter Zijlstra <peterz@infradead•org>,
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, Jason Wang <jasowang@redhat•com>,
kvm@vger•kernel.org, virtualization@lists•linux-foundation.org,
netdev@vger•kernel.org
Subject: Re: [PATCH tip/core/rcu 21/21] drivers/vhost: Remove now-redundant read_barrier_depends()
Date: Tue, 5 Dec 2017 12:08:01 -0800 [thread overview]
Message-ID: <20171205200801.GR7829@linux.vnet.ibm.com> (raw)
In-Reply-To: <20171205215020-mutt-send-email-mst@kernel.org>
On Tue, Dec 05, 2017 at 09:51:48PM +0200, Michael S. Tsirkin wrote:
> On Tue, Dec 05, 2017 at 11:33:39AM -0800, Paul E. McKenney wrote:
> > On Tue, Dec 05, 2017 at 09:24:21PM +0200, Michael S. Tsirkin wrote:
[ . . . ]
> > > and this barrier is no longer paired with anything until
> > > you realize there's a dependency barrier within READ_ONCE.
> > >
> > > Barrier pairing was a useful tool to check code validity,
> > > maybe there are other, better tools now.
> >
> > There are quite a few people who say that smp_store_release() is
> > easier for the tools to analyze than is smp_wmb(). My experience with
> > smp_read_barrier_depends() and rcu_dereference() leads me to believe
> > that they are correct.
>
> OK, but smp_store_release is still not paired with anything since we
> rely on READ_ONCE to include the implicit dpendendency barrier.
Why wouldn't you consider the smp_store_release() to be paired with
the new improved READ_ONCE()?
Thanx, Paul
next prev parent reply other threads:[~2017-12-05 20:08 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20171201195053.GA23494@linux.vnet.ibm.com>
2017-12-01 19:50 ` [PATCH tip/core/rcu 03/21] drivers/net/ethernet/qlogic/qed: Fix __qed_spq_block() ordering Paul E. McKenney
2017-12-01 19:51 ` [PATCH tip/core/rcu 14/21] netfilter: Remove now-redundant smp_read_barrier_depends() Paul E. McKenney
2017-12-01 19:51 ` [PATCH tip/core/rcu 21/21] drivers/vhost: Remove now-redundant read_barrier_depends() Paul E. McKenney
2017-12-05 18:31 ` Michael S. Tsirkin
2017-12-05 18:39 ` Peter Zijlstra
2017-12-05 18:57 ` Michael S. Tsirkin
2017-12-05 19:17 ` Peter Zijlstra
2017-12-05 19:24 ` Michael S. Tsirkin
2017-12-05 19:33 ` Paul E. McKenney
2017-12-05 19:51 ` Michael S. Tsirkin
2017-12-05 19:57 ` Peter Zijlstra
2017-12-05 20:28 ` Michael S. Tsirkin
2017-12-05 21:17 ` Peter Zijlstra
2017-12-05 21:42 ` Michael S. Tsirkin
2017-12-05 20:08 ` Paul E. McKenney [this message]
2017-12-05 21:24 ` Michael S. Tsirkin
2017-12-05 21:36 ` Paul E. McKenney
2017-12-05 21:43 ` Michael S. Tsirkin
2017-12-05 22:02 ` Paul E. McKenney
2017-12-05 22:09 ` Peter Zijlstra
2017-12-05 21:57 ` Peter Zijlstra
2017-12-05 22:09 ` Michael S. Tsirkin
2017-12-05 23:39 ` Paul E. McKenney
2017-12-05 19:55 ` Peter Zijlstra
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