From: Peter Zijlstra <peterz@infradead.org>
To: Will Deacon <will.deacon@arm.com>
Cc: "Maciej W. Rozycki" <macro@imgtec.com>,
"David Daney" <ddaney@caviumnetworks.com>,
"Måns Rullgård" <mans@mansr.com>,
"Ralf Baechle" <ralf@linux-mips.org>,
linux-kernel@vger.kernel.org,
"Paul McKenney" <paulmck@linux.vnet.ibm.com>,
torvalds@linux-foundation.org, boqun.feng@gmail.com
Subject: Re: [RFC][PATCH] mips: Fix arch_spin_unlock()
Date: Wed, 27 Jan 2016 15:54:21 +0100 [thread overview]
Message-ID: <20160127145421.GT6357@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20160127114348.GF2390@arm.com>
On Wed, Jan 27, 2016 at 11:43:48AM +0000, Will Deacon wrote:
> Do you know whether a SYNC 18 (RELEASE) followed in program order by a
> SYNC 17 (ACQUIRE) creates a full barrier (i.e. something like SYNC 16)?
>
> If not, you may need to implement smp_mb__after_unlock_lock for RCU
> to ensure globally transitive unlock->lock ordering should you decide
> to relax your locking barriers.
You know that is a tricky question. Maybe its easier if you give the 3
cpu litmus test that goes with it.
Maciej, the tricky point is what, if any, effect the
SYNC_RELEASE+SYNC_ACQUIRE pair has on an unrelated CPU. Please review
the TRANSITIVITY section in Documentation/memory-barriers.txt and
replace <general barrier> with the RELEASE+ACQUIRE pair.
We've all (Will, Paul and me) had much 'fun' trying to decipher the
MIPS64r6 manual but failed to reach a conclusion on this.
next prev parent reply other threads:[~2016-01-27 14:54 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-12 12:31 [RFC][PATCH] mips: Fix arch_spin_unlock() Peter Zijlstra
2015-11-12 12:35 ` Peter Zijlstra
2015-11-12 13:31 ` Måns Rullgård
2015-11-12 14:32 ` Paul E. McKenney
2015-11-12 14:50 ` Måns Rullgård
2015-11-12 14:59 ` Paul E. McKenney
2015-11-12 17:46 ` David Daney
2015-11-12 18:00 ` Peter Zijlstra
2015-11-12 18:13 ` Måns Rullgård
2015-11-12 18:17 ` David Daney
2016-01-27 9:57 ` Maciej W. Rozycki
2016-01-27 11:43 ` Will Deacon
2016-01-27 12:41 ` Maciej W. Rozycki
2016-01-28 1:11 ` Boqun Feng
2016-01-27 14:54 ` Peter Zijlstra [this message]
2016-01-27 15:21 ` Will Deacon
2016-01-27 23:38 ` Paul E. McKenney
2016-01-28 9:57 ` Will Deacon
2016-01-28 22:31 ` Paul E. McKenney
2016-01-29 9:59 ` Will Deacon
2016-01-29 10:22 ` Paul E. McKenney
2016-02-01 13:56 ` Will Deacon
2016-02-02 3:54 ` Paul E. McKenney
2016-02-02 5:19 ` Boqun Feng
2016-02-02 6:44 ` Paul E. McKenney
2016-02-02 8:07 ` Linus Torvalds
2016-02-02 8:19 ` Linus Torvalds
2016-02-02 9:34 ` Boqun Feng
2016-02-02 17:30 ` Linus Torvalds
2016-02-02 17:51 ` Will Deacon
2016-02-02 18:06 ` Linus Torvalds
2016-02-02 19:30 ` Will Deacon
2016-02-02 19:55 ` Linus Torvalds
2016-02-03 19:13 ` Will Deacon
2016-02-03 8:33 ` Ingo Molnar
2016-02-03 13:32 ` Will Deacon
2016-02-03 19:03 ` Will Deacon
2016-02-09 11:23 ` Ingo Molnar
2016-02-09 11:42 ` Will Deacon
2016-02-02 12:02 ` Paul E. McKenney
2016-02-02 17:56 ` Linus Torvalds
2016-02-02 22:30 ` Paul E. McKenney
2016-02-02 14:49 ` Ralf Baechle
2016-02-02 14:54 ` Måns Rullgård
2016-02-02 14:58 ` Ralf Baechle
2016-02-02 15:51 ` Måns Rullgård
2016-02-02 17:23 ` Peter Zijlstra
2016-02-02 22:38 ` Paul E. McKenney
2016-02-02 11:45 ` Will Deacon
2016-02-02 12:12 ` Boqun Feng
2016-02-02 12:20 ` Will Deacon
2016-02-02 13:18 ` Boqun Feng
2016-02-02 17:12 ` Paul E. McKenney
2016-02-02 17:37 ` Will Deacon
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