linux-kernel - Re: Adding plain accesses and detecting data races in the LKMM

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Date:   Fri, 19 Apr 2019 02:53:02 +0200
From:   Andrea Parri <andrea.parri@...rulasolutions.com>
To:     Alan Stern <stern@...land.harvard.edu>
Cc:     "Paul E. McKenney" <paulmck@...ux.ibm.com>,
        LKMM Maintainers -- Akira Yokosawa <akiyks@...il.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Daniel Lustig <dlustig@...dia.com>,
        David Howells <dhowells@...hat.com>,
        Jade Alglave <j.alglave@....ac.uk>,
        Luc Maranget <luc.maranget@...ia.fr>,
        Nicholas Piggin <npiggin@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will.deacon@....com>,
        Daniel Kroening <kroening@...ox.ac.uk>,
        Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: Adding plain accesses and detecting data races in the LKMM

> Are you saying that on x86, atomic_inc() acts as a full memory barrier 
> but not as a compiler barrier, and vice versa for 
> smp_mb__after_atomic()?  Or that neither atomic_inc() nor 
> smp_mb__after_atomic() implements a full memory barrier?

I'd say the former; AFAICT, these boil down to:

  https://elixir.bootlin.com/linux/v5.1-rc5/source/arch/x86/include/asm/atomic.h#L95
  https://elixir.bootlin.com/linux/v5.1-rc5/source/arch/x86/include/asm/barrier.h#L84

  Andrea