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

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Message-ID: <20140915163935.GB22768@redhat.com>
Date:	Mon, 15 Sep 2014 18:39:35 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Roman Pen <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 09/15, Roman Pen wrote:
>
> +static DECLARE_COMPLETION(rootfs_mounted);
> +
> +void wait_for_rootfs(void)
> +{
> +	/* Avoid waiting for ourselves */
> +	if (is_global_init(current))
> +		pr_warn("it is not a good idea to wait for rootfs mount from init task\n");
> +	else
> +		wait_for_completion(&rootfs_mounted);
> +}
> +
> +static inline void wake_up_rootfs_waiters(void)
> +{
> +	complete(&rootfs_mounted);
> +}

Probably you need complete_all() ?

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.

Oleg.

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