linux-kernel - Re: [RFC 09/15] PM / Hibernate: user, implement user

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Message-ID: <20100324204259.GA6423@elf.ucw.cz>
Date:	Wed, 24 Mar 2010 21:42:59 +0100
From:	Pavel Machek <pavel@....cz>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	jirislaby@...il.com, linux-pm@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org,
	Nigel Cunningham <ncunningham@...a.org.au>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [RFC 09/15] PM / Hibernate: user, implement user_ops writer

Hi!

> Switch /dev/snapshot writer to sws_module_ops approach so that we
> can transparently rewrite the rest of the snapshot from pages pulling
> to their pushing through layers.
> 
> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
> Cc: Nigel Cunningham <ncunningham@...a.org.au>
> Cc: "Rafael J. Wysocki" <rjw@...k.pl>
> ---
>  kernel/power/user.c |  113 +++++++++++++++++++++++++++++++++++++++++++++++----
>  1 files changed, 105 insertions(+), 8 deletions(-)
>

> +	if (test_bit(TODO_CLOSED, to_do_flags))
> +		return -EIO;
> +
> +	to_do_buf = buf;
> +	wmb();
> +	set_bit(TODO_WORK, to_do_flags);
> +	wake_up_interruptible(&to_do_wait);

Uhuh, open-coded barriers... these need to be commented, and I guess
you just should not play this kind of trickery.

spnlocks? Normal locks?

> +
> +	wait_event(to_do_done, !test_bit(TODO_WORK, to_do_flags) ||
> +			(err = test_bit(TODO_CLOSED, to_do_flags)));
> +
> +	return err ? -EIO : 0;
> +}
> +
> +static int put_user_writer(unsigned int flags, int error)
> +{
> +	int err = 0;
> +
> +	if (error)
> +		set_bit(TODO_ERROR, to_do_flags);
> +	set_bit(TODO_FINISH, to_do_flags);
> +	wake_up_interruptible(&to_do_wait);
> +
> +	wait_event(to_do_done, !test_bit(TODO_FINISH, to_do_flags) ||
> +			(err = test_bit(TODO_CLOSED, to_do_flags)));
> +
> +	if (!error && err)
> +		error = -EIO;
> +
> +	return error;
> +}
> +
>  struct sws_module_ops user_ops = {
									Pavel

-- 
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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