linux-kernel - Re: [v3 PATCH 1/1] init: fix race between rootfs mount and firmware loading

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Message-ID: <CACZ9PQWDynSqUREO_79e5DFKqhV62ra3ecYYaNttOdNx4wS6_A@mail.gmail.com>
Date:	Fri, 19 Sep 2014 21:41:09 +0900
From:	Roman Peniaev <r.peniaev@...il.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ming Lei <ming.lei@...onical.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [v3 PATCH 1/1] init: fix race between rootfs mount and firmware loading

On Fri, Sep 19, 2014 at 2:41 AM, Oleg Nesterov <oleg@...hat.com> wrote:
> On 09/18, Roman Pen wrote:
>>
>> +void wait_for_rootfs(void)
>> +{
>> +     /* Avoid waiting for ourselves */
>> +     if (WARN_ON(is_global_init(current)))
>> +             return;
>> +     else
>> +             wait_event(rootfs_waitq, rootfs_mounted);
>> +}
>
> Ah, wait, the is_global_init() check doesn't look right in any case.
>
> What if /sbin/init does sys_init_module() and this module does
> request_firmware() ?

Yeah, right. It turned out to be more tricky than I expected.
Will fix.

>
> I think we should only warn if init is going to wait,
>
>         /* Avoid waiting for ourselves */
>         if (rootfs_mounted || WARN_ON(is_global_init(current)))
>                 return;
>
>         __wait_event(rootfs_waitq, rootfs_mounted);
>
>
>> +EXPORT_SYMBOL(wait_for_rootfs);
>
> Why?

CONFIG_FW_LOADER (which includes firmware_class.c to compilation
sequence) is declared as tristate,
thus it can be built as module. Seems I can break  loading of this
module if skip exporting, right?

--
Roman
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