linux-kernel - Re: [Update][PATCH] PM / Hibernate: Fix s2disk regression related to unlock_system

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Date:	Wed, 18 Jan 2012 08:58:47 -0800
From:	Tejun Heo <tj@...nel.org>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux PM list <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>, horms@...ge.net.au,
	"pavel@....cz" <pavel@....cz>, Len Brown <lenb@...nel.org>
Subject: Re: [Update][PATCH] PM / Hibernate: Fix s2disk regression related to unlock_system_sleep()

Hello,

On Wed, Jan 18, 2012 at 8:54 AM, Srivatsa S. Bhat
<srivatsa.bhat@...ux.vnet.ibm.com> wrote:
> +       /*
> +        * Don't use freezer_count() because we don't want the call to
> +        * try_to_freeze() here.
> +        *
> +        * Reason:
> +        * unlock_system_sleep() gets called in snapshot_read() and
> +        * snapshot_write() when the freezing condition is still in effect.
> +        * Which means, if we use try_to_freeze() here, it would make them
> +        * enter the refrigerator, thus causing suspend-to-disk to lockup.
> +        */

Yeap, much better but wouldn't it be better if the description was
higher level?  ie. Explain why try_to_freeze() doesn't make sense for
this operation semantically and then, optionally, give an example of
breakage.  It usually is lack of proper rationale / reasoning that
confuses people reading the code.

Thank you.

-- 
tejun
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