linux-kernel - Re: [PATCH V4 1/2] ACPI / EC: Fix broken 64bit big-endian users of 'global

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Message-ID: <4357538.Wlf88yQie6@vostro.rjw.lan>
Date:	Fri, 25 Sep 2015 22:33:24 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Johannes Berg <johannes@...solutions.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linaro-kernel@...ts.linaro.org,
	QCA ath9k Development <ath9k-devel@....qualcomm.com>,
	Intel Linux Wireless <ilw@...ux.intel.com>,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-acpi@...r.kernel.org,
	linux-bluetooth@...r.kernel.org, iommu@...ts.linux-foundation.org,
	netdev@...r.kernel.org, linux-wireless@...r.kernel.org,
	linux-scsi@...r.kernel.org, linux-usb@...r.kernel.org,
	linux-edac@...r.kernel.org, linux-mm@...ck.org,
	alsa-devel@...a-project.org
Subject: Re: [PATCH V4 1/2] ACPI / EC: Fix broken 64bit big-endian users of 'global_lock'

On Friday, September 25, 2015 10:26:22 PM Rafael J. Wysocki wrote:
> On Friday, September 25, 2015 11:52:56 AM Viresh Kumar wrote:
> > On 25-09-15, 20:49, Johannes Berg wrote:
> > > Ok, then, but that means Rafael is completely wrong ...
> > > debugfs_create_bool() takes a *pointer* and it needs to be long-lived,
> > > it can't be on the stack. You also don't get a call when it changes.
> > 
> > Ahh, ofcourse. My bad as well...
> 
> Well, sorry about the wrong suggestion.
> 
> > I think we can change structure definition but will wait for Rafael's
> > comment before that.
> 
> OK, change the structure then.

But here's a question.

You're going to change that into bool in the next patch, right?

So what if bool is a byte and the field is not word-aligned and changing
that byte requires a read-modify-write.  How do we ensure that things remain
consistent in that case?

Thanks,
Rafael

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