linux-kernel - Re: [PATCH v2 1/4] mm: fix exec activate_mm vs TLB shootdown and lazy tlb switching race

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Message-ID: <87a6xn6zx7.fsf@mpe.ellerman.id.au>
Date:   Fri, 18 Sep 2020 22:18:44 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Nicholas Piggin <npiggin@...il.com>, peterz@...radead.org
Cc:     Jens Axboe <axboe@...nel.dk>, linux-arch@...r.kernel.org,
        "linux-mm \@ kvack . org" <linux-mm@...ck.org>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        linux-kernel@...r.kernel.org,
        Andy Lutomirski <luto@...capital.net>,
        Dave Hansen <dave.hansen@...el.com>,
        sparclinux@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        linuxppc-dev@...ts.ozlabs.org,
        "David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH v2 1/4] mm: fix exec activate_mm vs TLB shootdown and lazy tlb switching race

Nicholas Piggin <npiggin@...il.com> writes:
> Excerpts from peterz@...radead.org's message of September 14, 2020 8:56 pm:
>> On Mon, Sep 14, 2020 at 02:52:16PM +1000, Nicholas Piggin wrote:
>>> Reading and modifying current->mm and current->active_mm and switching
>>> mm should be done with irqs off, to prevent races seeing an intermediate
>>> state.
...
>>> 
>>> This is a bit ugly, but in the interest of fixing the bug and backporting
>>> before all architectures are converted this is a compromise.
>>> 
>>> Signed-off-by: Nicholas Piggin <npiggin@...il.com>
>> 
>> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
>> 
>> I'm thinking we want this selected on x86 as well. Andy?
>
> Thanks for the ack. The plan was to take it through the powerpc tree,
> but if you'd want x86 to select it, maybe a topic branch?

I've put this series in a topic branch based on v5.9-rc2:

  https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/log/?h=topic/irqs-off-activate-mm

I plan to merge it into the powerpc/next tree for v5.10, but if anyone
else wants to merge it that's fine too.

cheers