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From: Luis Chamberlain <mcgrof@kernel.org>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Jessica Yu <jeyu@kernel.org>, Borislav Petkov <bp@alien8.de>,
	Jonathan Corbet <corbet@lwn.net>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-kernel@vger.kernel.org,
	Nick Desaulniers <ndesaulniers@google.com>
Subject: Re: [PATCH v3 2/2] modules: add CONFIG_MODPROBE_PATH
Date: Mon, 15 Mar 2021 20:06:55 +0000	[thread overview]
Message-ID: <20210315200655.GX4332@42.do-not-panic.com> (raw)
In-Reply-To: <20210313212528.2956377-3-linux@rasmusvillemoes.dk>

On Sat, Mar 13, 2021 at 10:25:28PM +0100, Rasmus Villemoes wrote:
> Allow the developer to specifiy the initial value of the
> modprobe_path[] string. This can be used to set it to the empty string
> initially, thus effectively disabling request_module() during early
> boot until userspace writes a new value via the
> /proc/sys/kernel/modprobe interface. [1]
> 
> When building a custom kernel (often for an embedded target), it's
> normal to build everything into the kernel that is needed for booting,
> and indeed the initramfs often contains no modules at all, so every
> such request_module() done before userspace init has mounted the real
> rootfs is a waste of time.
> 
> This is particularly useful when combined with the previous patch,
> which made the initramfs unpacking asynchronous - for that to work, it
> had to make any usermodehelper call wait for the unpacking to finish
> before attempting to invoke the userspace helper. By eliminating all
> such (known-to-be-futile) calls of usermodehelper, the initramfs
> unpacking and the {device,late}_initcalls can proceed in parallel for
> much longer.
> 
> For a relatively slow ppc board I'm working on, the two patches
> combined lead to 0.2s faster boot - but more importantly, the fact
> that the initramfs unpacking proceeds completely in the background
> while devices get probed means I get to handle the gpio watchdog in
> time without getting reset.
> 
> [1] __request_module() already has an early -ENOENT return when
> modprobe_path is the empty string.
> 
> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Acked-by: Jessica Yu <jeyu@kernel.org>
> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>

Acked-by: Luis Chamberlain <mcgrof@kernel.org>

  Luis

  reply	other threads:[~2021-03-15 20:07 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
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 [this message]
2021-03-15 20:23 ` [PATCH v3 0/2] background initramfs unpacking, and CONFIG_MODPROBE_PATH Luis Chamberlain

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