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From: Christopher Lameter <cl@linux.com>
To: Paul Walmsley <paul.walmsley@sifive.com>
Cc: "Nick Kossifidis" <mick@ics.forth.gr>,
	"Björn Töpel" <bjorn.topel@gmail.com>,
	"Paul Walmsley" <paul@pwsan.com>,
	"Palmer Dabbelt" <palmer@sifive.com>,
	linux-riscv@lists.infradead.org
Subject: Re: per-cpu thoughts
Date: Fri, 1 Mar 2019 01:13:26 +0000	[thread overview]
Message-ID: <0100016936d02cf1-2a096483-1c87-4889-879a-9eb2f4f1e77c-000000@email.amazonses.com> (raw)
In-Reply-To: <alpine.DEB.2.21.9999.1902281217250.17965@viisi.sifive.com>

On Thu, 28 Feb 2019, Paul Walmsley wrote:

> Is the offset of the counter from the start of my per-cpu area guaranteed
> to be the same across all CPUs?  If so, wouldn't there simply be a

Yes of course otherwise it would work. The per cpu area is replicated
across all processors on bootup.

> potential performance risk if preemption was left enabled, rather than a
> correctness risk?

An unlocked RMW write operation can corrupt data because it may race with
another unlocked RMW write operation on another processor. Writesto the
per cpu data must always occur from the processor that owns the area.



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  reply	other threads:[~2019-03-01  1:13 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-20 19:57 per-cpu thoughts Björn Töpel
2019-02-21 15:57 ` Christopher Lameter
2019-02-21 16:28 ` Paul Walmsley
2019-02-21 17:24   ` Björn Töpel
2019-02-21 17:49     ` Paul Walmsley
2019-02-21 19:40       ` Palmer Dabbelt
2019-02-22 15:04         ` Christopher Lameter
2019-02-22 15:36           ` Nick Kossifidis
2019-02-22 15:56             ` Christopher Lameter
2019-02-22 19:47               ` Björn Töpel
2019-02-22 19:56                 ` Christopher Lameter
2019-02-28 12:20                   ` Paul Walmsley
2019-02-28 17:58                     ` Christopher Lameter
2019-02-28 18:42                       ` Paul Walmsley
2019-02-28 19:09                         ` Christopher Lameter
2019-02-28 20:21                           ` Paul Walmsley
2019-03-01  1:13                             ` Christopher Lameter [this message]
2019-03-08  7:17                   ` Björn Töpel
2019-03-11 13:22                     ` Palmer Dabbelt
2019-03-11 14:48                       ` Björn Töpel
2019-03-11 14:56                         ` Christopher Lameter
2019-03-11 15:05                           ` Björn Töpel
2019-03-11 15:26                             ` Paul Walmsley
2019-03-11 15:26                               ` Paul Walmsley
2019-03-11 16:48                               ` Mark Rutland
2019-03-11 16:48                                 ` Mark Rutland
2019-03-11 18:39                                 ` Paul Walmsley
2019-03-11 18:39                                   ` Paul Walmsley
2019-03-12 11:23                                   ` Mark Rutland
2019-03-12 11:23                                     ` Mark Rutland
2019-03-12 16:01                                     ` Paul Walmsley
2019-03-12 16:01                                       ` Paul Walmsley
2019-03-12 17:34                                       ` Christopher Lameter
2019-03-12 17:34                                         ` Christopher Lameter
2019-03-12  4:26                               ` Christopher Lameter
2019-03-12  4:26                                 ` Christopher Lameter
2019-03-12 14:21                                 ` Paul Walmsley
2019-03-12 14:21                                   ` Paul Walmsley
2019-03-12 17:42                                   ` Christopher Lameter
2019-03-12 17:42                                     ` Christopher Lameter
2019-03-12 17:59                                     ` Gary Guo
2019-03-12 17:59                                       ` Gary Guo
2019-03-13 18:58                                       ` Christopher Lameter
2019-03-13 18:58                                         ` Christopher Lameter
2019-03-13 20:15                                     ` Paul Walmsley
2019-03-13 20:15                                       ` Paul Walmsley
2019-03-22 14:51                               ` Nick Kossifidis
2019-03-22 14:51                                 ` Nick Kossifidis
2019-03-22 17:57                                 ` Christopher Lameter
2019-03-22 17:57                                   ` Christopher Lameter
2019-03-11 15:51                             ` Christopher Lameter
2019-03-11 16:35                               ` Björn Töpel
2019-03-12  4:22                                 ` Christopher Lameter
2019-02-22 19:48             ` Björn Töpel
2019-02-22 20:53               ` Nick Kossifidis

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