linux-kernel - Re: [RFC PATCH] riscv/locking: Strengthen spin_lock() and spin

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Message-ID: <20180222182717.GS25181@hirez.programming.kicks-ass.net>
Date:   Thu, 22 Feb 2018 19:27:17 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     Daniel Lustig <dlustig@...dia.com>,
        Andrea Parri <parri.andrea@...il.com>,
        linux-kernel@...r.kernel.org, Palmer Dabbelt <palmer@...ive.com>,
        Albert Ou <albert@...ive.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Will Deacon <will.deacon@....com>,
        Boqun Feng <boqun.feng@...il.com>,
        Nicholas Piggin <npiggin@...il.com>,
        David Howells <dhowells@...hat.com>,
        Jade Alglave <j.alglave@....ac.uk>,
        Luc Maranget <luc.maranget@...ia.fr>,
        Akira Yokosawa <akiyks@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-riscv@...ts.infradead.org
Subject: Re: [RFC PATCH] riscv/locking: Strengthen spin_lock() and
 spin_unlock()

On Thu, Feb 22, 2018 at 10:13:17AM -0800, Paul E. McKenney wrote:
> So we have something that is not all that rare in the Linux kernel
> community, namely two conflicting more-or-less concurrent changes.
> This clearly needs to be resolved, either by us not strengthening the
> Linux-kernel memory model in the way we were planning to or by you
> strengthening RISC-V to be no weaker than PowerPC for these sorts of
> externally viewed release-acquire situations.
> 
> Other thoughts?

Like said in the other email, I would _much_ prefer to not go weaker
than PPC, I find that PPC is already painfully weak at times.