linux-kernel - Re: [RFC][RFT][PATCH] ACPI: Protection from suspending in the middle of EC transaction

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Date:	Sun, 31 Jan 2010 14:11:21 +0000
From:	Alan Jenkins <sourcejedi.lkml@...glemail.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Alexey Starikovskiy <astarikovskiy@...e.de>,
	Len Brown <lenb@...nel.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	Thomas Renninger <trenn@...e.de>,
	Maxim Levitsky <maximlevitsky@...il.com>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][RFT][PATCH] ACPI: Protection from suspending in the middle 
	of EC transaction

On 1/30/10, Rafael J. Wysocki <rjw@...k.pl> wrote:
> Hi,
>
> While Maxim is testing if the patch below helps with
> http://bugzilla.kernel.org/show_bug.cgi?id=14668
> I think it's necessary anyway.
>
> The problem is that currently there's nothing to prevent us from suspending
> in
> the middle of an EC transaction in progress, at least as far as I can see.
> As a result, we can suspend with the ACPI global lock held or something like
> this, which leads to problems especially for hibernation (if the resume
> kernel
> passes control to the image kernel in the middle of an EC transaction,
> things
> aren't nice).  For this reason I think we should wait until there are no EC
> transactions in progress before we suspend and we should prevent any new
> EC transactions from starting after that point.  The patch below does that.

I also believe this is a problem.  I reported the following -

<http://bugzilla.kernel.org/show_bug.cgi?id=14112> "Pressing acpi
hotkeys duing hibernation may occasionally cause EC transaction
timeout"

and posted a patch, but I couldn't reproduce my specific issue in
order to confirm that the patch helped.

Regards
Alan
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