linux-kernel - Re: [RFC PATCH 0/2] kmod: Support lockup option to make module un-removable

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Message-ID: <87mw90eg3o.fsf@rustcorp.com.au>
Date:	Mon, 13 Oct 2014 15:11:31 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Lucas De Marchi <lucas.de.marchi@...il.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Lucas De Marchi <lucas.demarchi@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-modules <linux-modules@...r.kernel.org>,
	Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [RFC PATCH 0/2] kmod: Support lockup option to make module un-removable

Lucas De Marchi <lucas.de.marchi@...il.com> writes:
> On Tue, Aug 26, 2014 at 9:04 AM, Masami Hiramatsu
> <masami.hiramatsu.pt@...achi.com> wrote:
>> Hi,
>>
>> Here is a pair of patches which adds --lockup option to
>> modprobe and libkmod.
>>
>> As I sent a series of patches which removes stop_machine()
>> from module removal: https://lkml.org/lkml/2014/8/25/142
>> it also adds lockup option which lock up the module in
>> the kernel and makes it un-removable.
>>
>> These patches enables us to use that option when loading
>> modules. Module lockup may be good for BIG SMP machines
>> since the kernel skips module refcounting if the module
>> is locked up :)
>>
>> Anyway, this is not needed if the lockup option is dropped
>> from the series. I send this for testing.
>
> Ok. I'm not sure it's clear... I'm waiting for feedback on the kernel
> patches in order to proceed with any review here. I'm not really
> convinced we want this option when loading a module.
>
> Rusty, what do you think?

I'm not convinced, I asked him to drop that patch.  If we have
significant performance issues, we'll have to do something smarter I
think anyway.

Cheers,
Rusty.
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