From: Michael Ellerman <mpe@ellerman.id.au>
To: paulmck@linux.vnet.ibm.com
Cc: Will Deacon <will.deacon@arm.com>,
Peter Zijlstra <peterz@infradead.org>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [RFC PATCH v2] memory-barriers: remove smp_mb__after_unlock_lock()
Date: Mon, 17 Aug 2015 14:06:07 +1000 [thread overview]
Message-ID: <1439784367.14494.3.camel@ellerman.id.au> (raw)
In-Reply-To: <20150812154346.GR3895@linux.vnet.ibm.com>
On Wed, 2015-08-12 at 08:43 -0700, Paul E. McKenney wrote:
> On Wed, Aug 12, 2015 at 02:44:15PM +0100, Will Deacon wrote:
> > Hello Paul,
> >
> > On Fri, Jul 24, 2015 at 04:30:46PM +0100, Paul E. McKenney wrote:
> > > On Fri, Jul 24, 2015 at 12:31:01PM +0100, Will Deacon wrote:
> > > > On Wed, Jul 15, 2015 at 02:12:21PM +0100, Paul E. McKenney wrote:
> > > > > > > commit 695c05d4b9666c50b40a1c022678b5f6e2e3e771
> > > > > > > Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > > > > > > Date: Tue Jul 14 18:35:23 2015 -0700
> > > > > > >
> > > > > > > rcu,locking: Privatize smp_mb__after_unlock_lock()
> > > > > > >
> > > > > > > RCU is the only thing that uses smp_mb__after_unlock_lock(), and is
> > > > > > > likely the only thing that ever will use it, so this commit makes this
> > > > > > > macro private to RCU.
> > > > > > >
> > > > > > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > > > > > > Cc: Will Deacon <will.deacon@arm.com>
> > > > > > > Cc: Peter Zijlstra <peterz@infradead.org>
> > > > > > > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> > > > > > > Cc: "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>
> > > >
> > > > Are you planning to queue this somewhere? I think it makes sense regardless
> > > > of whether we change PowerPc or not and ideally it would be merged around
> > > > the same time as my relaxed atomics series.
> > >
> > > I have is in -rcu. By default, I will push it to the 4.4 merge window.
> > > Please let me know if you need it sooner.
> >
> > The generic relaxed atomics are now queued in -tip, so it would be really
> > good to see this Documentation update land in 4.3 if at all possible. I
> > appreciate it's late in the cycle, but it's always worth asking.
>
> Can't hurt to give it a try. I have set -rcu's rcu/next branch to this
> commit, and if it passes a few day's worth of testing, I will see what
> Ingo has to say about a pull request.
>
> This commit also privatizes smp_mb__after_unlock_lock() as well as
> updating documentation. Looks like we need to strengthen powerpc's
> locking primitives, then get rid of smp_mb__after_unlock_lock() entirely.
> Or did that already happen and I just missed it?
No it didn't.
I thought the end result of this thread was that we didn't *need* to change the
powerpc lock semantics? Or did I read it wrong?
ie. the docs now say that RELEASE+ACQUIRE is not a full barrier, which is
consistent with our current implementation.
cheers
next prev parent reply other threads:[~2015-08-17 4:06 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-13 12:15 [RFC PATCH v2] memory-barriers: remove smp_mb__after_unlock_lock() Will Deacon
2015-07-13 13:09 ` Peter Hurley
2015-07-13 14:24 ` Will Deacon
2015-07-13 15:56 ` Peter Zijlstra
2015-07-13 13:11 ` Peter Zijlstra
2015-07-13 14:09 ` Will Deacon
2015-07-13 14:21 ` Will Deacon
2015-07-13 15:54 ` Peter Zijlstra
2015-07-13 17:50 ` Will Deacon
2015-07-13 20:20 ` Paul E. McKenney
2015-07-13 22:23 ` Peter Zijlstra
2015-07-13 23:04 ` Paul E. McKenney
2015-07-14 10:04 ` Will Deacon
2015-07-14 12:45 ` Paul E. McKenney
2015-07-14 12:51 ` Will Deacon
2015-07-14 14:00 ` Paul E. McKenney
2015-07-14 14:12 ` Will Deacon
2015-07-14 19:31 ` Paul E. McKenney
2015-07-15 1:38 ` Paul E. McKenney
2015-07-15 10:51 ` Will Deacon
2015-07-15 13:12 ` Paul E. McKenney
2015-07-24 11:31 ` Will Deacon
2015-07-24 15:30 ` Paul E. McKenney
2015-08-12 13:44 ` Will Deacon
2015-08-12 15:43 ` Paul E. McKenney
2015-08-12 17:59 ` Paul E. McKenney
2015-08-13 10:49 ` Will Deacon
2015-08-13 13:10 ` Paul E. McKenney
2015-08-17 4:06 ` Michael Ellerman [this message]
2015-08-17 6:15 ` Paul E. McKenney
2015-08-17 8:57 ` Will Deacon
2015-08-18 1:50 ` Michael Ellerman
2015-08-18 8:37 ` Will Deacon
2015-08-20 9:45 ` Michael Ellerman
2015-08-20 15:56 ` Will Deacon
2015-08-26 0:27 ` Paul E. McKenney
2015-08-26 4:06 ` Michael Ellerman
2015-07-13 18:23 ` Paul E. McKenney
2015-07-13 19:41 ` Peter Hurley
2015-07-13 20:16 ` Paul E. McKenney
2015-07-13 22:15 ` Peter Zijlstra
2015-07-13 22:43 ` Benjamin Herrenschmidt
2015-07-14 8:34 ` Peter Zijlstra
2015-07-13 22:53 ` Paul E. McKenney
2015-07-13 22:37 ` Benjamin Herrenschmidt
2015-07-13 22:31 ` Benjamin Herrenschmidt
2015-07-14 10:16 ` Will Deacon
2015-07-15 3:06 ` Michael Ellerman
2015-07-15 10:44 ` Will Deacon
2015-07-16 2:00 ` Michael Ellerman
2015-07-16 5:03 ` Benjamin Herrenschmidt
2015-07-16 5:14 ` Benjamin Herrenschmidt
2015-07-16 15:11 ` Paul E. McKenney
2015-07-16 22:54 ` Benjamin Herrenschmidt
2015-07-17 9:32 ` Will Deacon
2015-07-17 10:15 ` Peter Zijlstra
2015-07-17 12:40 ` Paul E. McKenney
2015-07-17 22:14 ` Benjamin Herrenschmidt
2015-07-20 13:39 ` Will Deacon
2015-07-20 13:48 ` Paul E. McKenney
2015-07-20 13:56 ` Will Deacon
2015-07-20 21:18 ` Benjamin Herrenschmidt
2015-07-22 16:49 ` Will Deacon
2015-09-01 2:57 ` Paul Mackerras
2015-07-15 14:18 ` Paul E. McKenney
2015-07-16 1:34 ` Michael Ellerman
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