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From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>,
	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>,
	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: Sat, 23 Nov 2013 22:29:29 +0100	[thread overview]
Message-ID: <20131123212929.GP4971@laptop.programming.kicks-ass.net> (raw)
In-Reply-To: <CA+55aFxQy8afgf6geqJOEHmsJ=ME-6CXrrPfj=aggH7u_jEEZA@mail.gmail.com>

On Sat, Nov 23, 2013 at 12:21:13PM -0800, Linus Torvalds wrote:
> *SOME* assumption of mine must be wrong. But I don't see which one.

I haven't read your email in full detail yet, but one thing I did miss
was cache-snoops.

One of the reasons for failing transitive / multi-copy atomicity is that
CPUs might have different views of the memory state depending on from
which caches they can get snoops.

Eg. if CPU0 and CPU1 share a cache level but CPU2 does not, CPU1 might
observe a write before CPU2 can.

--
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WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>,
	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>,
	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>,
	"H. Peter Anvin" <hpa@zytor.com>, Arnd Bergmann <arnd@arndb.de>,
	Aswin Chandramouleeswaran <aswin@hp.com>,
	Scott J Norton <scott.norton@hp.com>,
	"Figo.zhang" <figo1802@gmail.com>
Subject: Re: [PATCH v6 4/5] MCS Lock: Barrier corrections
Date: Sat, 23 Nov 2013 22:29:29 +0100	[thread overview]
Message-ID: <20131123212929.GP4971@laptop.programming.kicks-ass.net> (raw)
In-Reply-To: <CA+55aFxQy8afgf6geqJOEHmsJ=ME-6CXrrPfj=aggH7u_jEEZA@mail.gmail.com>

On Sat, Nov 23, 2013 at 12:21:13PM -0800, Linus Torvalds wrote:
> *SOME* assumption of mine must be wrong. But I don't see which one.

I haven't read your email in full detail yet, but one thing I did miss
was cache-snoops.

One of the reasons for failing transitive / multi-copy atomicity is that
CPUs might have different views of the memory state depending on from
which caches they can get snoops.

Eg. if CPU0 and CPU1 share a cache level but CPU2 does not, CPU1 might
observe a write before CPU2 can.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

  parent reply	other threads:[~2013-11-23 21:29 UTC|newest]

Thread overview: 239+ 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  1:37   ` Tim Chen
2013-11-20 10:19   ` Will Deacon
2013-11-20 10:19     ` Will Deacon
2013-11-20 12:50     ` Paul E. McKenney
2013-11-20 12:50       ` Paul E. McKenney
2013-11-20 17:00       ` Will Deacon
2013-11-20 17:00         ` Will Deacon
2013-11-20 17:14         ` Paul E. McKenney
2013-11-20 17:14           ` Paul E. McKenney
2013-11-20 17:00     ` Tim Chen
2013-11-20 17:00       ` Tim Chen
2013-11-20 17:16       ` Paul E. McKenney
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   ` 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   ` 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   ` 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  1:37   ` Tim Chen
2013-11-20 15:31   ` Paul E. McKenney
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 15:46       ` Will Deacon
2013-11-20 17:14       ` Paul E. McKenney
2013-11-20 17:14         ` Paul E. McKenney
2013-11-20 18:43         ` Tim Chen
2013-11-20 18:43           ` Tim Chen
2013-11-20 19:06           ` Paul E. McKenney
2013-11-20 19:06             ` Paul E. McKenney
2013-11-20 20:36             ` Tim Chen
2013-11-20 20:36               ` Tim Chen
2013-11-20 21:44               ` Paul E. McKenney
2013-11-20 21:44                 ` Paul E. McKenney
2013-11-20 23:51                 ` Tim Chen
2013-11-20 23:51                   ` Tim Chen
2013-11-21  4:53                   ` Paul E. McKenney
2013-11-21  4:53                     ` Paul E. McKenney
2013-11-21 10:17                     ` Will Deacon
2013-11-21 10:17                       ` Will Deacon
2013-11-21 13:16                       ` Paul E. McKenney
2013-11-21 13:16                         ` Paul E. McKenney
2013-11-21 10:45                     ` Peter Zijlstra
2013-11-21 10:45                       ` Peter Zijlstra
2013-11-21 13:18                       ` Paul E. McKenney
2013-11-21 13:18                         ` Paul E. McKenney
2013-11-21 22:27                     ` Linus Torvalds
2013-11-21 22:27                       ` Linus Torvalds
2013-11-21 22:52                       ` Paul E. McKenney
2013-11-21 22:52                         ` Paul E. McKenney
2013-11-22  0:09                         ` Linus Torvalds
2013-11-22  0:09                           ` Linus Torvalds
2013-11-22  4:08                           ` Paul E. McKenney
2013-11-22  4:08                             ` Paul E. McKenney
2013-11-22  4:25                             ` Linus Torvalds
2013-11-22  4:25                               ` Linus Torvalds
2013-11-22  6:23                               ` Paul E. McKenney
2013-11-22  6:23                                 ` Paul E. McKenney
2013-11-22 15:16                                 ` Ingo Molnar
2013-11-22 15:16                                   ` Ingo Molnar
2013-11-22 18:49                                   ` Paul E. McKenney
2013-11-22 18:49                                     ` Paul E. McKenney
2013-11-22 19:06                                     ` Linus Torvalds
2013-11-22 19:06                                       ` Linus Torvalds
2013-11-22 20:06                                       ` Paul E. McKenney
2013-11-22 20:06                                         ` Paul E. McKenney
2013-11-22 20:09                                         ` Linus Torvalds
2013-11-22 20:09                                           ` Linus Torvalds
2013-11-22 20:37                                           ` Paul E. McKenney
2013-11-22 20:37                                             ` Paul E. McKenney
2013-11-22 21:01                                             ` Linus Torvalds
2013-11-22 21:01                                               ` Linus Torvalds
2013-11-22 21:52                                               ` Paul E. McKenney
2013-11-22 21:52                                                 ` Paul E. McKenney
2013-11-22 22:19                                                 ` Linus Torvalds
2013-11-22 22:19                                                   ` Linus Torvalds
2013-11-23  0:25                                                   ` Paul E. McKenney
2013-11-23  0:25                                                     ` Paul E. McKenney
2013-11-23  0:42                                                     ` Linus Torvalds
2013-11-23  0:42                                                       ` Linus Torvalds
2013-11-23  1:36                                                       ` Paul E. McKenney
2013-11-23  1:36                                                         ` Paul E. McKenney
2013-11-23  2:11                                                         ` Linus Torvalds
2013-11-23  2:11                                                           ` Linus Torvalds
2013-11-23  4:05                                                           ` Paul E. McKenney
2013-11-23  4:05                                                             ` Paul E. McKenney
2013-11-23 11:24                                                             ` Ingo Molnar
2013-11-23 11:24                                                               ` Ingo Molnar
2013-11-23 17:06                                                               ` Paul E. McKenney
2013-11-23 17:06                                                                 ` Paul E. McKenney
2013-11-26 12:02                                                                 ` Ingo Molnar
2013-11-26 12:02                                                                   ` Ingo Molnar
2013-11-26 19:28                                                                   ` Paul E. McKenney
2013-11-26 19:28                                                                     ` Paul E. McKenney
2013-11-23 20:21                                                         ` Linus Torvalds
2013-11-23 20:21                                                           ` Linus Torvalds
2013-11-23 20:39                                                           ` Linus Torvalds
2013-11-23 20:39                                                             ` Linus Torvalds
2013-11-25 12:09                                                             ` Peter Zijlstra
2013-11-25 12:09                                                               ` Peter Zijlstra
2013-11-25 17:18                                                               ` Will Deacon
2013-11-25 17:18                                                                 ` Will Deacon
2013-11-25 17:56                                                                 ` Paul E. McKenney
2013-11-25 17:56                                                                   ` Paul E. McKenney
2013-11-25 17:54                                                             ` Paul E. McKenney
2013-11-25 17:54                                                               ` Paul E. McKenney
2013-11-23 21:29                                                           ` Peter Zijlstra [this message]
2013-11-23 21:29                                                             ` Peter Zijlstra
2013-11-23 22:24                                                             ` Linus Torvalds
2013-11-23 22:24                                                               ` Linus Torvalds
2013-11-25 17:53                                                           ` Paul E. McKenney
2013-11-25 17:53                                                             ` Paul E. McKenney
2013-11-25 18:21                                                             ` Peter Zijlstra
2013-11-25 18:21                                                               ` Peter Zijlstra
2013-11-21 11:03         ` Peter Zijlstra
2013-11-21 11:03           ` Peter Zijlstra
2013-11-21 12:56           ` Peter Zijlstra
2013-11-21 12:56             ` Peter Zijlstra
2013-11-21 13:20             ` Paul E. McKenney
2013-11-21 13:20               ` Paul E. McKenney
2013-11-21 17:25               ` Paul E. McKenney
2013-11-21 17:25                 ` Paul E. McKenney
2013-11-21 21:52                 ` Peter Zijlstra
2013-11-21 21:52                   ` Peter Zijlstra
2013-11-21 22:18                   ` Paul E. McKenney
2013-11-21 22:18                     ` Paul E. McKenney
2013-11-22 15:58                     ` Peter Zijlstra
2013-11-22 15:58                       ` Peter Zijlstra
2013-11-22 18:26                       ` Paul E. McKenney
2013-11-22 18:26                         ` Paul E. McKenney
2013-11-22 18:51                         ` Peter Zijlstra
2013-11-22 18:51                           ` Peter Zijlstra
2013-11-22 18:59                           ` Paul E. McKenney
2013-11-22 18:59                             ` Paul E. McKenney
2013-11-25 17:35                           ` Peter Zijlstra
2013-11-25 17:35                             ` Peter Zijlstra
2013-11-25 18:02                             ` Paul E. McKenney
2013-11-25 18:02                               ` Paul E. McKenney
2013-11-25 18:24                               ` Peter Zijlstra
2013-11-25 18:24                                 ` Peter Zijlstra
2013-11-25 18:34                                 ` Tim Chen
2013-11-25 18:34                                   ` Tim Chen
2013-11-25 18:27                               ` Peter Zijlstra
2013-11-25 18:27                                 ` Peter Zijlstra
2013-11-25 23:52                                 ` Paul E. McKenney
2013-11-25 23:52                                   ` Paul E. McKenney
2013-11-26  9:59                                   ` Peter Zijlstra
2013-11-26  9:59                                     ` Peter Zijlstra
2013-11-26 17:11                                     ` Paul E. McKenney
2013-11-26 17:11                                       ` Paul E. McKenney
2013-11-26 17:18                                       ` Peter Zijlstra
2013-11-26 17:18                                         ` Peter Zijlstra
2013-11-26 19:00                                     ` Linus Torvalds
2013-11-26 19:00                                       ` Linus Torvalds
2013-11-26 19:20                                       ` Paul E. McKenney
2013-11-26 19:20                                         ` Paul E. McKenney
2013-11-26 19:32                                         ` Linus Torvalds
2013-11-26 19:32                                           ` Linus Torvalds
2013-11-26 22:51                                           ` Paul E. McKenney
2013-11-26 22:51                                             ` Paul E. McKenney
2013-11-26 23:58                                             ` Linus Torvalds
2013-11-26 23:58                                               ` Linus Torvalds
2013-11-27  0:21                                               ` Thomas Gleixner
2013-11-27  0:21                                                 ` Thomas Gleixner
2013-11-27  0:39                                               ` Paul E. McKenney
2013-11-27  0:39                                                 ` Paul E. McKenney
2013-11-27  1:05                                                 ` Linus Torvalds
2013-11-27  1:05                                                   ` Linus Torvalds
2013-11-27  1:31                                                   ` Paul E. McKenney
2013-11-27  1:31                                                     ` Paul E. McKenney
2013-11-27 10:16                                             ` Will Deacon
2013-11-27 10:16                                               ` Will Deacon
2013-11-27 17:11                                               ` Paul E. McKenney
2013-11-27 17:11                                                 ` Paul E. McKenney
2013-11-28 11:40                                                 ` Will Deacon
2013-11-28 11:40                                                   ` Will Deacon
2013-11-28 17:38                                                   ` Paul E. McKenney
2013-11-28 17:38                                                     ` Paul E. McKenney
2013-11-28 18:03                                                     ` Will Deacon
2013-11-28 18:03                                                       ` Will Deacon
2013-11-28 18:27                                                       ` Paul E. McKenney
2013-11-28 18:27                                                         ` Paul E. McKenney
2013-11-28 18:53                                                         ` Will Deacon
2013-11-28 18:53                                                           ` Will Deacon
2013-11-28 19:50                                                           ` Paul E. McKenney
2013-11-28 19:50                                                             ` Paul E. McKenney
2013-11-29 16:17                                                             ` Will Deacon
2013-11-29 16:17                                                               ` Will Deacon
2013-11-29 16:44                                                               ` Linus Torvalds
2013-11-29 16:44                                                                 ` Linus Torvalds
2013-11-29 18:18                                                                 ` Will Deacon
2013-11-29 18:18                                                                   ` Will Deacon
2013-11-30 17:38                                                                 ` Paul E. McKenney
2013-11-30 17:38                                                                   ` Paul E. McKenney
2013-11-26 19:21                                       ` Peter Zijlstra
2013-11-26 19:21                                         ` Peter Zijlstra
2013-11-27 16:58                                         ` Oleg Nesterov
2013-11-27 16:58                                           ` Oleg Nesterov
2013-11-26 23:08                                       ` Benjamin Herrenschmidt
2013-11-26 23:08                                         ` Benjamin Herrenschmidt
2013-11-25 23:55                               ` H. Peter Anvin
2013-11-25 23:55                                 ` H. Peter Anvin
2013-11-26  3:16                                 ` Paul E. McKenney
2013-11-26  3:16                                   ` Paul E. McKenney
2013-11-27  0:46                                   ` H. Peter Anvin
2013-11-27  0:46                                     ` H. Peter Anvin
2013-11-27  1:07                                     ` Linus Torvalds
2013-11-27  1:07                                       ` Linus Torvalds
2013-11-27  1:27                                     ` Paul E. McKenney
2013-11-27  1:27                                       ` Paul E. McKenney
2013-11-27  2:59                                       ` H. Peter Anvin
2013-11-27  2:59                                         ` H. Peter Anvin
2013-11-25 18:52                             ` H. Peter Anvin
2013-11-25 18:52                               ` H. Peter Anvin
2013-11-25 22:58                               ` Tim Chen
2013-11-25 22:58                                 ` Tim Chen
2013-11-25 23:28                                 ` H. Peter Anvin
2013-11-25 23:28                                   ` H. Peter Anvin
2013-11-25 23:51                                   ` Paul E. McKenney
2013-11-25 23:51                                     ` Paul E. McKenney
2013-11-25 23:36                               ` Paul E. McKenney
2013-11-25 23:36                                 ` Paul E. McKenney
2013-12-04 21:26                 ` Andi Kleen
2013-12-04 21:26                   ` Andi Kleen
2013-12-04 22:07                   ` Paul E. McKenney
2013-12-04 22:07                     ` Paul E. McKenney
2013-11-21 13:19           ` 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
2013-11-20  1:37   ` Tim Chen

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