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From: Peter Zijlstra <peterz@infradead.org>
To: David Daney <ddaney@caviumnetworks.com>
Cc: ralf@linux-mips.org, linux-kernel@vger.kernel.org,
	Paul McKenney <paulmck@linux.vnet.ibm.com>,
	Will Deacon <will.deacon@arm.com>,
	torvalds@linux-foundation.org, boqun.feng@gmail.com
Subject: Re: [RFC][PATCH] mips: Fix arch_spin_unlock()
Date: Thu, 12 Nov 2015 19:00:03 +0100	[thread overview]
Message-ID: <20151112180003.GE17308@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <5644D08D.4080206@caviumnetworks.com>

On Thu, Nov 12, 2015 at 09:46:53AM -0800, David Daney wrote:

> For CONFIG_CPU_CAVIUM_OCTEON the proper thing would be:
> 
>     smp_wmb();
>     smp_rmb();
> 
> Which expands to exactly the same thing as wmb() because smp_rmb() expands
> to nothing.

OK, so the current code isn't broken because for Cavium wmb is suffient
because rmb is a no-op, and for !Cavium wmb expands to SYNC.

> You yourself seem to have added smp_store_release(), so we could even do:
> 
>      smp_store_release(&lock->h.serving_now, lock->h.serving_now + 1);
> 
> That would leave us to cook up a proper definition of smp_store_release().

That is indeed the better solution.

  reply	other threads:[~2015-11-12 18:00 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 [this message]
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
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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