linux-kernel - Re: bio linked list corruption.

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Message-ID: <CA+55aFzPPz9E6=0qGO2QbTx6E0hWogORgQ-0NSsmw9jmLLwSwQ@mail.gmail.com>
Date:   Mon, 5 Dec 2016 10:25:46 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Vegard Nossum <vegard.nossum@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Dave Jones <davej@...emonkey.org.uk>, Chris Mason <clm@...com>,
        Jens Axboe <axboe@...com>, Al Viro <viro@...iv.linux.org.uk>,
        Josef Bacik <jbacik@...com>, David Sterba <dsterba@...e.com>,
        linux-btrfs <linux-btrfs@...r.kernel.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        Dave Chinner <david@...morbit.com>
Subject: Re: bio linked list corruption.

On Mon, Dec 5, 2016 at 10:11 AM, Andy Lutomirski <luto@...nel.org> wrote:
>
> So your kernel has been smp-alternatived.  That 3e comes from
> alternatives_smp_unlock.  If you're running on SMP with UP
> alternatives, things will break.

I'm assuming he's just running in a VM with a single CPU.

The problem that I pointed out with assuming wake_up_all() actually
removes all wait queue entries does not depend on SMP. The race is
much more fundamental and long-lived.

               Linus