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

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Date:   Wed, 28 Jul 2021 12:36:50 +0200
From:   Alexander Egorenkov <egorenar@...ux.ibm.com>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux@...musvillemoes.dk
Cc:     akpm@...ux-foundation.org, bp@...en8.de, corbet@....net,
        gregkh@...uxfoundation.org, jeyu@...nel.org,
        linux-kernel@...r.kernel.org, mcgrof@...nel.org,
        ndesaulniers@...gle.com, torvalds@...ux-foundation.org,
        Bruno Goncalves <bgoncalv@...hat.com>,
        Dave Young <dyoung@...hat.com>
Subject: Re: [PATCH v3 1/2] init/initramfs.c: do unpacking asynchronously

Rasmus Villemoes <linux@...musvillemoes.dk> writes:

> 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.
>

Thanks for the helpful explanation. I disabled UEVENT on my test machine and
as you said, the message is being triggered by request_module() now.

[    3.396467]  [<00000001f8d917e4>] call_usermodehelper_exec+0x44/0x1c8
[    3.396470]  [<00000001f8da5524>] __request_module+0x17c/0x3d0
[    3.396473]  [<00000001f93b4808>] crypto_alg_mod_lookup+0x228/0x290
[    3.396475]  [<00000001f93b4aae>] crypto_alloc_tfm_node+0x5e/0x158
[    3.396477]  [<00000001f93bbe14>] crypto_alloc_shash+0x34/0x40
[    3.396480]  [<00000001f93d2ee2>] drbg_init_hash_kernel+0x3a/0x100
[    3.396482]  [<00000001f93d306e>] drbg_alloc_state+0xc6/0x280
[    3.396484]  [<00000001f93d33d8>] drbg_kcapi_seed+0x1b0/0x310
[    3.396486]  [<00000001f93d1884>] crypto_rng_reset+0x5c/0xe0
[    3.396488]  [<00000001f93c1750>] alg_test_drbg+0x300/0x478
[    3.396490]  [<00000001f93c0934>] alg_test+0x304/0x530
[    3.396493]  [<00000001f93bedb8>] cryptomgr_test+0x68/0x70
[    3.396495]  [<00000001f8d9f40c>] kthread+0x14c/0x160
[    3.396497]  [<00000001f8d2af14>] __ret_from_fork+0x3c/0x58
[    3.396500]  [<00000001f984c86a>] ret_from_fork+0xa/0x30

Regards
Alex