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From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: Alexander Egorenkov <egorenar@linux.ibm.com>, linux@rasmusvillemoes.dk
Cc: akpm@linux-foundation.org, bp@alien8.de, corbet@lwn.net,
	gregkh@linuxfoundation.org, jeyu@kernel.org,
	linux-kernel@vger.kernel.org, mcgrof@kernel.org,
	ndesaulniers@google.com, torvalds@linux-foundation.org,
	Bruno Goncalves <bgoncalv@redhat.com>,
	Dave Young <dyoung@redhat.com>
Subject: Re: [PATCH v3 1/2] init/initramfs.c: do unpacking asynchronously
Date: Mon, 26 Jul 2021 13:46:03 +0200	[thread overview]
Message-ID: <edb79b68-6dd0-ced5-17a0-fda7516d3529@rasmusvillemoes.dk> (raw)
In-Reply-To: <87sg04p315.fsf@oc8242746057.ibm.com>

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

While that message was added as part of the same patch, it's a red
herring: It merely means that something ends up calling usermodehelper
(perhaps a request_module) before the init sequence has come around to
rootfs_initcalls. At that point, the rootfs is (with or without my async
patch) entirely empty, so those usermodehelper calls have always failed
with -ENOENT.

If you have CONFIG_UEVENT_HELPER=y and CONFIG_UEVENT_HELPER_PATH set to
a non-empty string, you can try setting the latter to the empty string.
But the message won't go away if it's really a request_module() and not
a uevent notification.

> [    6.599433] rootfs image is not initramfs (broken padding); looks like an initrd
> [    6.669373] Freeing initrd memory: 24828K
> 
> It is very hard to reproduce, i haven't managed to do it yet and working
> on it, but it occurs regularly, nearly every day once but only on a particular
> test machine with our nightly s390 CI test runs.

So this looks somewhat similar to a ppc64 report

https://lore.kernel.org/lkml/CA+QYu4qxf2CYe2gC6EYnOHXPKS-+cEXL=MnUvqRFaN7W1i6ahQ@mail.gmail.com/T/#u

that ended up not being caused by e7cb072eb988, since it could also be
reproduced with that patch reverted. I don't know if Bruno found the
root cause, adding him to cc. Also cc += Dave Young who had some input
in that thread.

> Although the initramfs corruption is hard to reproduce,
> the message 'wait_for_initramfs() called before rootfs_initcalls'
> appears regularly on each boot at least since 2021-06-24 which we just
> noticed a couple of days ago.
> 
> Appending 'initramfs_async=0' to the kernel command-line doesn't seem to
> help with the 'wait_for_initramfs' message and i can still see it.

Yes, that's expected. I should probably send a patch to move
usermodehelper_enable() from do_basic_setup() to populate_rootfs(), as
it really doesn't make sense to have usermodehelper enabled before
there's any content in the file system. But as I said, the warning is
harmless and merely indicates there's a bunch of futile work being done
to call a (at that point in time) non-existing usermode program.

> [    0.890962] wait_for_initramfs() called before rootfs_initcalls
...
> [    1.636419] Trying to unpack rootfs image as initramfs...
> [    1.676907] Freeing initrd memory: 26056K

It would be interesting if you could boot with initramfs_async=0 enough
times to see if you can reproduce the problem; and/or do the same with
e7cb072eb988 reverted.

Thanks,
Rasmus

  reply	other threads:[~2021-07-26 11:46 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-13 21:25 [PATCH v3 0/2] background initramfs unpacking, and CONFIG_MODPROBE_PATH Rasmus Villemoes
2021-03-13 21:25 ` [PATCH v3 1/2] init/initramfs.c: do unpacking asynchronously Rasmus Villemoes
2021-03-15 20:21   ` Luis Chamberlain
2021-03-15 21:33   ` Andrew Morton
2021-03-15 21:59     ` Rasmus Villemoes
2021-07-24  7:46   ` Alexander Egorenkov
2021-07-26 11:46     ` Rasmus Villemoes [this message]
2021-07-27  7:31       ` Bruno Goncalves
2021-07-27 13:54         ` Luis Chamberlain
2021-07-27 14:12           ` Bruno Goncalves
2021-07-27 14:21             ` Luis Chamberlain
2021-07-27 14:27               ` Bruno Goncalves
2021-07-27 14:42                 ` Luis Chamberlain
2021-07-27 14:48                   ` Bruno Goncalves
2021-07-28 10:44                   ` Alexander Egorenkov
2021-07-28 10:38           ` Alexander Egorenkov
2021-07-28 10:36       ` Alexander Egorenkov
2021-07-28 11:49         ` Rasmus Villemoes
2021-03-13 21:25 ` [PATCH v3 2/2] modules: add CONFIG_MODPROBE_PATH Rasmus Villemoes
2021-03-15 20:06   ` Luis Chamberlain
2021-03-15 20:23 ` [PATCH v3 0/2] background initramfs unpacking, and CONFIG_MODPROBE_PATH Luis Chamberlain

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