linux-kernel - Re: Q&A from "Concurrency with tools/memory-model"

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Date:   Tue, 27 Nov 2018 12:55:37 +0100
From:   Andrea Parri <andrea.parri@...rulasolutions.com>
To:     "Paul E. McKenney" <paulmck@...ux.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        mingo@...nel.org, stern@...land.harvard.edu,
        parri.andrea@...il.com, will.deacon@....com, peterz@...radead.org,
        boqun.feng@...il.com, npiggin@...il.com, dhowells@...hat.com,
        j.alglave@....ac.uk, luc.maranget@...ia.fr, akiyks@...il.com
Subject: Re: Q&A from "Concurrency with tools/memory-model"

On Thu, Nov 15, 2018 at 02:56:30PM -0800, Paul E. McKenney wrote:
> Hello!
> 
> Good turnout and some good questions here in Vancouver BC, please see
> below for rough notes.  ;-)

Thanks for the notes.  I attach here the slides used for the talk
(so let's see how many typos I've left...).

  Andrea


> 
> 							Thanx, Paul
> 
> ------------------------------------------------------------------------
> 
> "Concurrency with tools/memory-model"
> 
> Andrea Parri presenting.
> 
> Rough notes of Q&A.
> 
> o	Want atomic bit operation.
> 
> o	But smp_read_barrier_depends() not there, so how to note pairing?
> 	A:  Note the dependency as the other end of the pairing.
> 
> o	Speculation barriers, as in Spectre and Meltdown?  A: This would
> 	require adding timing, not in the immediate future.
> 
> o	What ordering does system calls provide?  A: None that we know of.
> 	Boqun: Userspace needs to explicitly provide the needed ordering
> 	when interacting with the kernel.  Some architectures do provide
> 	full barriers, but not to be counted on.
> 
> o	Why herd7?  A: Based on other formalizations -- note that herd7
> 	had a number of hardware models.  Paul: Plus the founder of the
> 	LKMM project is a co-author of herd, which might have had some
> 	effect.
> 
> o	Why not also model interrupts and NMIs?  Promela and spin have
> 	been used for this.  A: Cannot currently model them.  You can
> 	emulated them with additional threads and locks, if you wish.
> 	Vincent Nimal and Lihao Liang have done some academic work on
> 	these topics.
> 

Download attachment "slides.pdf" of type "application/pdf" (137134 bytes)