linux-kernel - Re: [PATCH 2/8] x86: use exit_lazy_tlb rather than membarrier_mm_sync_core_before

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Message-ID: <CALCETrV5BzXuUYm5YAoEKPZZPfLrbHckvwBHzWKrxZS8hqzHEg@mail.gmail.com>
Date:   Thu, 10 Dec 2020 16:11:36 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Nicholas Piggin <npiggin@...il.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Anton Blanchard <anton@...abs.org>,
        Arnd Bergmann <arnd@...db.de>,
        linux-arch <linux-arch@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Peter Zijlstra <peterz@...radead.org>, X86 ML <x86@...nel.org>
Subject: Re: [PATCH 2/8] x86: use exit_lazy_tlb rather than membarrier_mm_sync_core_before_usermode

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