From: Jessica Yu <jeyu@kernel.org>
To: Adam Zabrocki <pi3@pi3.com.pl>
Cc: Nicolas Morey-Chaisemartin <nmoreychaisemartin@suse.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org, Solar Designer <solar@openwall.com>
Subject: Re: Linux Kernel module notification bug
Date: Mon, 11 Jan 2021 15:20:48 +0100 [thread overview]
Message-ID: <20210111142048.GA27038@linux-8ccs> (raw)
In-Reply-To: <20210110175401.GB32505@pi3.com.pl>
+++ Adam Zabrocki [10/01/21 18:54 +0100]:
>Hello,
>
>I believe that the following commit does introduce a gentle "functionality
>bug":
>
>"module: delay kobject uevent until after module init call":
>https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/kernel/module.c?id=38dc717e97153e46375ee21797aa54777e5498f3
>
>The official Linux Kernel API for the kernel module activities notification has
>been divided based on the readiness 'stage' for such module. We have the
>following stages:
>
> MODULE_STATE_LIVE, /* Normal state. */
> MODULE_STATE_COMING, /* Full formed, running module_init. */
> MODULE_STATE_GOING, /* Going away. */
> MODULE_STATE_UNFORMED, /* Still setting it up. */
>
>LIVE means that the kernel module is correctly running and all initialization
>work has been already done. Otherwise, we have event 'COMING' or 'UNFORMED'.
>
>In the described commit, creation of the KOBJECT has been moved after invoking
>a notficiation of the newly formed kernel module state (LIVE). That's somehow
>inconsistent from my understanding of the kernel modules notifiers logic.
>Creation of the new objects (like KOBJ) should be done before notification of
>the stage LIVE is invoked.
I'm confused. We're not creating any kobjects here. That is all done
in mod_sysfs_setup(), which is called while the module is still
COMING. What that commit does is delay telling userspace about the
module (specifically, systemd/udev) until the module is basically
ready. Systemd was basically receiving the uevent too early, before
the module has initialized, hence we decided to delay the uevent [1].
>This commit breaks some of the projects that rely on the LIVE notification to
>monitor when the newly loaded module is ready.
Hm, could you please explain specifically what is the issue you're seeing?
What projects is it breaking?
Thanks,
Jessica
[1] https://github.com/systemd/systemd/issues/17586
next prev parent reply other threads:[~2021-01-11 14:21 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-10 17:54 Linux Kernel module notification bug Adam Zabrocki
2021-01-11 14:20 ` Jessica Yu [this message]
2021-01-12 0:15 ` Adam Zabrocki
2021-01-12 10:46 ` Jessica Yu
2021-01-12 11:00 ` Greg Kroah-Hartman
2021-01-13 0:33 ` [PATCH] module: invoke kobject uevent before sending LIVE notification Adam Zabrocki
2021-01-13 7:44 ` Greg Kroah-Hartman
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