linux-kernel - Re: [PATCH v3 1/2] init/initramfs.c: do unpacking asynchronously

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Message-ID: <CA+QYu4qSw_W=hdOARxjfisRjx4Lpy-MSe1ZovfUtVb2GGMynkg@mail.gmail.com>
Date:   Tue, 27 Jul 2021 16:12:54 +0200
From:   Bruno Goncalves <bgoncalv@...hat.com>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Alexander Egorenkov <egorenar@...ux.ibm.com>,
        akpm@...ux-foundation.org, bp@...en8.de, corbet@....net,
        gregkh@...uxfoundation.org, jeyu@...nel.org,
        linux-kernel@...r.kernel.org, ndesaulniers@...gle.com,
        torvalds@...ux-foundation.org, Dave Young <dyoung@...hat.com>
Subject: Re: [PATCH v3 1/2] init/initramfs.c: do unpacking asynchronously

On Tue, Jul 27, 2021 at 3:55 PM Luis Chamberlain <mcgrof@...nel.org> wrote:
>
> On Tue, Jul 27, 2021 at 09:31:54AM +0200, Bruno Goncalves wrote:
> > On Mon, Jul 26, 2021 at 1:46 PM Rasmus Villemoes
> > <linux@...musvillemoes.dk> wrote:
> > >
> > > On 24/07/2021 09.46, Alexander Egorenkov wrote:
> > > > Hello,
> > > >
> > > > since e7cb072eb988 ("init/initramfs.c: do unpacking asynchronously"), we
> > > > started seeing the following problem on s390 arch regularly:
> > > >
> > > > [    5.039734] wait_for_initramfs() called before rootfs_initcalls
>
> So some context here, which might help.
>
> The initramfs_cookie is initialized until a a rootfs_initcall() is
> called, in this case populate_rootfs(). The code is small, so might
> as well include it:
>
> static int __init populate_rootfs(void)
> {
>         initramfs_cookie = async_schedule_domain(do_populate_rootfs, NULL,
>                                                  &initramfs_domain);
>         if (!initramfs_async)
>                 wait_for_initramfs();
>         return 0;
> }
> rootfs_initcall(populate_rootfs);
>
> The warning you see comes from a situation where a wait_for_initramfs()
> gets called but we haven't yet initialized initramfs_cookie.  There are
> only a few calls for wait_for_initramfs() in the kernel, and the only
> thing I can think of is that somehow s390 may rely on a usermode helper
> early on, but not every time.
>
> What umh calls does s390 issue?
>
> > Unfortunately, we haven't been able to find the root cause, but since
> > June 23rd we haven't hit this panic...
> >
> > Btw, this panic we were hitting only when testing kernels from "scsi"
> > and "block" trees.
>
> Do you use drdb maybe?

No, the machines we were able to reproduce the problem don't have drdb.

Bruno
>
>   Luis
>