Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <1607152918.fkgmomgfw9.astroid@bobo.none> <116A6B40-C77B-4B6A-897B-18342CD62CEC@amacapital.net>
 <1607209402.fogfsh8ov4.astroid@bobo.none> <CALCETrWFjOXAd5=ctX3tzgUbyfwM+bT-f8WY_QWOeuDdFxhWbg@mail.gmail.com>
 <1607224014.8xeujbleij.astroid@bobo.none>
In-Reply-To: <1607224014.8xeujbleij.astroid@bobo.none>
From:   Andy Lutomirski <luto@kernel.org>
Date:   Thu, 10 Dec 2020 16:11:36 -0800
Message-ID: <CALCETrV5BzXuUYm5YAoEKPZZPfLrbHckvwBHzWKrxZS8hqzHEg@mail.gmail.com>
Subject: Re: [PATCH 2/8] x86: use exit_lazy_tlb rather than membarrier_mm_sync_core_before_usermode
To:     Nicholas Piggin <npiggin@gmail.com>
Cc:     Andy Lutomirski <luto@kernel.org>,
        Anton Blanchard <anton@ozlabs.org>,
        Arnd Bergmann <arnd@arndb.de>,
        linux-arch <linux-arch@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Peter Zijlstra <peterz@infradead.org>, X86 ML <x86@kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

> On Dec 5, 2020, at 7:59 PM, Nicholas Piggin <npiggin@gmail.com> wrote:
>

> I'm still going to persue shoot-lazies for the merge window. As you
> see it's about a dozen lines and a if (IS_ENABLED(... in core code.
> Your change is common code, but a significant complexity (which
> affects all archs) so needs a lot more review and testing at this
> point.

I don't think it's ready for this merge window.  I read the early
patches again, and I think they make the membarrier code worse, not
better.  I'm not fundamentally opposed to the shoot-lazies concept,
but it needs more thought and it needs a cleaner foundation.