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

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Message-ID: <20140917175944.GD19308@redhat.com>
Date:	Wed, 17 Sep 2014 19:59:44 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Roman Peniaev <r.peniaev@...il.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: [PATCH 1/1] init: fix race between rootfs mount and firmware
	loading

On 09/17, Roman Peniaev wrote:
>
> On Tue, Sep 16, 2014 at 1:39 AM, Oleg Nesterov <oleg@...hat.com> wrote:
> > On 09/15, Roman Pen wrote:
> >>
> >
> > Otherwise wait_for_rootfs() can return only once, the next call will block
> > forever. And perhaps it would be better to use another primitive, even if
> > UINT_MAX/2 should be enough.
>
> And why do you think completion is not good for this?
> Seems it is impossible to have so many threads on early init, which wait
> for rootfs.

Yes, but it is not only called during init? Suppose that a user does
insmod + rmmod in a loop, and the driver calls request_firmware(). This
will hang after UINT_MAX/2 iterations. Sure, this can't happen in practice,
but still this doesn't look good imho.

Oleg.

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