linux-kernel - Re: [RFC 0/3] tools/memory-model: Add litmus tests for atomic APIs

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Date:   Sat, 15 Feb 2020 07:39:21 +0800
From:   Boqun Feng <boqun.feng@...il.com>
To:     Alan Stern <stern@...land.harvard.edu>
Cc:     linux-kernel@...r.kernel.org,
        Andrea Parri <parri.andrea@...il.com>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Nicholas Piggin <npiggin@...il.com>,
        David Howells <dhowells@...hat.com>,
        Jade Alglave <j.alglave@....ac.uk>,
        Luc Maranget <luc.maranget@...ia.fr>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Akira Yokosawa <akiyks@...il.com>,
        Daniel Lustig <dlustig@...dia.com>,
        Jonathan Corbet <corbet@....net>, linux-arch@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [RFC 0/3] tools/memory-model: Add litmus tests for atomic APIs

On Fri, Feb 14, 2020 at 10:27:44AM -0500, Alan Stern wrote:
> On Fri, 14 Feb 2020, Boqun Feng wrote:
> 
> > A recent discussion raises up the requirement for having test cases for
> > atomic APIs:
> > 
> > 	https://lore.kernel.org/lkml/20200213085849.GL14897@hirez.programming.kicks-ass.net/
> > 
> > , and since we already have a way to generate a test module from a
> > litmus test with klitmus[1]. It makes sense that we add more litmus
> > tests for atomic APIs into memory-model.
> 
> It might be worth discussing this point a little more fully.  The 

I'm open to any suggestion, and ...

> set of tests in tools/memory-model/litmus-tests/ is deliberately rather 
> limited.  Paul has a vastly more expansive set of litmus tests in a 

I'm OK if we want to limit the number of litmus tests in
tools/memory-model/litmus-tests directory. But ...

> GitHub repository, and I am doubtful about how many new tests we want 
> to keep in the kernel source.
> 

I think we all agree we want to use litmus tests as much as possbile for
discussing locking/parallel programming/memory model related problems,
right? This is benefical for both kernel and the herd tool, as they can
improve each other.

Atomic APIs (perhaps even {READ,WRITE}_ONCE(), smp_load_acquire() and
smp_store_release()) have been longing for some more concrete examples
as a complement for the semantics description in the docs, so that
people can check their understandings. Further, with the help of
klitmus, the litmus tests can be a useful tool for testing if a new arch
support is added to kernel. That's why I plan to add litmus tests into
kernel source.

Thoughts?

Regards,
Boqun

> Perhaps it makes sense to have tests corresponding to all the examples
> in Documentation/, perhaps not.  How do people feel about this?
> 
> Alan
>