From: Linus Torvalds <torvalds@linux-foundation.org>
To: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>,
Tim Chen <tim.c.chen@linux.intel.com>,
Will Deacon <will.deacon@arm.com>, Ingo Molnar <mingo@elte.hu>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
Waiman Long <waiman.long@hp.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Alex Shi <alex.shi@linaro.org>, Andi Kleen <andi@firstfloor.org>,
Michel Lespinasse <walken@google.com>,
Davidlohr Bueso <davidlohr.bueso@hp.com>,
Matthew R Wilcox <matthew.r.wilcox@intel.com>,
Dave Hansen <dave.hansen@intel.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Rik van Riel <riel@redhat.com>,
Peter Hurley <peter@hurleysoftware.com>,
Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
George Spelvin <linux@horizon.com>
Subject: Re: [PATCH v6 4/5] MCS Lock: Barrier corrections
Date: Fri, 22 Nov 2013 18:11:52 -0800 [thread overview]
Message-ID: <CA+55aFyJRAX4e9H0AFGcPMrBBTmGC6K_iCCS3dc7Mx6ejTmYMA@mail.gmail.com> (raw)
In-Reply-To: <20131123013654.GG4138@linux.vnet.ibm.com>
On Fri, Nov 22, 2013 at 5:36 PM, Paul E. McKenney
<paulmck@linux.vnet.ibm.com> wrote:
>
> So there is your example. It really can and does happen.
>
> Again, easy fix. Just change powerpc's smp_store_release() from lwsync
> to smp_mb(). That fixes the problem and doesn't hurt anyone but powerpc.
>
> OK?
Hmm. Ok
Except now I'm worried it can happen on x86 too because my mental
model was clearly wrong.
x86 does have that extra "Memory ordering obeys causality (memory
ordering respects transitive visibility)." rule, and the example in
the architecture manual (section 8.2.3.6 "Stores Are Transitively
Visible") seems to very much about this, but your particular example
is subtly different, so..
I will have to ruminate on this.
Linus
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next prev parent reply other threads:[~2013-11-23 2:11 UTC|newest]
Thread overview: 123+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <cover.1384885312.git.tim.c.chen@linux.intel.com>
2013-11-20 1:37 ` [PATCH v6 0/5] MCS Lock: MCS lock code cleanup and optimizations Tim Chen
2013-11-20 1:37 ` Tim Chen
2013-11-20 10:19 ` Will Deacon
2013-11-20 12:50 ` Paul E. McKenney
2013-11-20 17:00 ` Will Deacon
2013-11-20 17:14 ` Paul E. McKenney
2013-11-20 17:00 ` Tim Chen
2013-11-20 17:16 ` Paul E. McKenney
2013-11-20 1:37 ` [PATCH v6 1/5] MCS Lock: Restructure the MCS lock defines and locking code into its own file Tim Chen
2013-11-20 1:37 ` Tim Chen
2013-11-20 1:37 ` [PATCH v6 2/5] MCS Lock: optimizations and extra comments Tim Chen
2013-11-20 1:37 ` Tim Chen
2013-11-20 1:37 ` [PATCH v6 3/5] MCS Lock: Move mcs_lock/unlock function into its own file Tim Chen
2013-11-20 1:37 ` Tim Chen
2013-11-20 1:37 ` [PATCH v6 4/5] MCS Lock: Barrier corrections Tim Chen
2013-11-20 1:37 ` Tim Chen
2013-11-20 15:31 ` Paul E. McKenney
2013-11-20 15:31 ` Paul E. McKenney
2013-11-20 15:46 ` Will Deacon
2013-11-20 17:14 ` Paul E. McKenney
2013-11-20 18:43 ` Tim Chen
2013-11-20 19:06 ` Paul E. McKenney
2013-11-20 20:36 ` Tim Chen
2013-11-20 21:44 ` Paul E. McKenney
2013-11-20 23:51 ` Tim Chen
2013-11-21 4:53 ` Paul E. McKenney
2013-11-21 10:17 ` Will Deacon
2013-11-21 13:16 ` Paul E. McKenney
2013-11-21 10:45 ` Peter Zijlstra
2013-11-21 13:18 ` Paul E. McKenney
2013-11-21 22:27 ` Linus Torvalds
2013-11-21 22:52 ` Paul E. McKenney
2013-11-22 0:09 ` Linus Torvalds
2013-11-22 4:08 ` Paul E. McKenney
2013-11-22 4:25 ` Linus Torvalds
2013-11-22 6:23 ` Paul E. McKenney
2013-11-22 15:16 ` Ingo Molnar
2013-11-22 18:49 ` Paul E. McKenney
2013-11-22 19:06 ` Linus Torvalds
2013-11-22 20:06 ` Paul E. McKenney
2013-11-22 20:09 ` Linus Torvalds
2013-11-22 20:37 ` Paul E. McKenney
2013-11-22 21:01 ` Linus Torvalds
2013-11-22 21:52 ` Paul E. McKenney
2013-11-22 22:19 ` Linus Torvalds
2013-11-23 0:25 ` Paul E. McKenney
2013-11-23 0:42 ` Linus Torvalds
2013-11-23 1:36 ` Paul E. McKenney
2013-11-23 2:11 ` Linus Torvalds [this message]
2013-11-23 4:05 ` Paul E. McKenney
2013-11-23 11:24 ` Ingo Molnar
2013-11-23 17:06 ` Paul E. McKenney
2013-11-26 12:02 ` Ingo Molnar
2013-11-26 19:28 ` Paul E. McKenney
2013-11-23 20:21 ` Linus Torvalds
2013-11-23 20:39 ` Linus Torvalds
2013-11-25 12:09 ` Peter Zijlstra
2013-11-25 17:18 ` Will Deacon
2013-11-25 17:56 ` Paul E. McKenney
2013-11-25 17:54 ` Paul E. McKenney
2013-11-23 21:29 ` Peter Zijlstra
2013-11-23 22:24 ` Linus Torvalds
2013-11-25 17:53 ` Paul E. McKenney
2013-11-25 18:21 ` Peter Zijlstra
2013-11-21 11:03 ` Peter Zijlstra
2013-11-21 12:56 ` Peter Zijlstra
2013-11-21 13:20 ` Paul E. McKenney
2013-11-21 17:25 ` Paul E. McKenney
2013-11-21 21:52 ` Peter Zijlstra
2013-11-21 22:18 ` Paul E. McKenney
2013-11-22 15:58 ` Peter Zijlstra
2013-11-22 18:26 ` Paul E. McKenney
2013-11-22 18:51 ` Peter Zijlstra
2013-11-22 18:59 ` Paul E. McKenney
2013-11-25 17:35 ` Peter Zijlstra
2013-11-25 18:02 ` Paul E. McKenney
2013-11-25 18:24 ` Peter Zijlstra
2013-11-25 18:34 ` Tim Chen
2013-11-25 18:27 ` Peter Zijlstra
2013-11-25 23:52 ` Paul E. McKenney
2013-11-26 9:59 ` Peter Zijlstra
2013-11-26 17:11 ` Paul E. McKenney
2013-11-26 17:18 ` Peter Zijlstra
2013-11-26 19:00 ` Linus Torvalds
2013-11-26 19:20 ` Paul E. McKenney
2013-11-26 19:32 ` Linus Torvalds
2013-11-26 22:51 ` Paul E. McKenney
2013-11-26 23:58 ` Linus Torvalds
2013-11-27 0:21 ` Thomas Gleixner
2013-11-27 0:39 ` Paul E. McKenney
2013-11-27 1:05 ` Linus Torvalds
2013-11-27 1:31 ` Paul E. McKenney
2013-11-27 10:16 ` Will Deacon
2013-11-27 17:11 ` Paul E. McKenney
2013-11-28 11:40 ` Will Deacon
2013-11-28 17:38 ` Paul E. McKenney
2013-11-28 18:03 ` Will Deacon
2013-11-28 18:27 ` Paul E. McKenney
2013-11-28 18:53 ` Will Deacon
2013-11-28 19:50 ` Paul E. McKenney
2013-11-29 16:17 ` Will Deacon
2013-11-29 16:44 ` Linus Torvalds
2013-11-29 18:18 ` Will Deacon
2013-11-30 17:38 ` Paul E. McKenney
2013-11-26 19:21 ` Peter Zijlstra
2013-11-27 16:58 ` Oleg Nesterov
2013-11-26 23:08 ` Benjamin Herrenschmidt
2013-11-25 23:55 ` H. Peter Anvin
2013-11-26 3:16 ` Paul E. McKenney
2013-11-27 0:46 ` H. Peter Anvin
2013-11-27 1:07 ` Linus Torvalds
2013-11-27 1:27 ` Paul E. McKenney
2013-11-27 2:59 ` H. Peter Anvin
2013-11-25 18:52 ` H. Peter Anvin
2013-11-25 22:58 ` Tim Chen
2013-11-25 23:28 ` H. Peter Anvin
2013-11-25 23:51 ` Paul E. McKenney
2013-11-25 23:36 ` Paul E. McKenney
2013-12-04 21:26 ` Andi Kleen
2013-12-04 22:07 ` Paul E. McKenney
2013-11-21 13:19 ` Paul E. McKenney
2013-11-20 1:37 ` [PATCH v6 5/5] MCS Lock: Allows for architecture specific mcs lock and unlock Tim Chen
2013-11-20 1:37 ` Tim Chen
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