linux-kernel - Re: [PATCH] drivers/usb: use READ_ONCE instead of deprecated ACCESS

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Date:   Mon, 21 Nov 2016 08:15:46 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Davidlohr Bueso <dave@...olabs.net>
Cc:     linux-kernel@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH] drivers/usb: use READ_ONCE instead of deprecated
 ACCESS_ONCE

On Sun, Nov 20, 2016 at 08:09:40AM -0800, Davidlohr Bueso wrote:
> Hi Greg!
> 
> On Sun, 20 Nov 2016, Greg KH wrote:
> 
> > On Sat, Nov 19, 2016 at 11:54:25AM -0800, Davidlohr Bueso wrote:
> > > With the new standardized functions, we can replace all ACCESS_ONCE()
> > > calls across relevant drivers/usb/.
> > > 
> > > ACCESS_ONCE() does not work reliably on non-scalar types. For example
> > > gcc 4.6 and 4.7 might remove the volatile tag for such accesses during
> > > the SRA (scalar replacement of aggregates) step:
> > > 
> > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145
> > > 
> > > Update the new calls regardless of if it is a scalar type, this is
> > > cleaner than having three alternatives.
> > > 
> > > Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
> > 
> > Nit, this doesn't match your From: line :(
> 
> That's on purpose, and all my patches are the same.

So they are all incorrect?  Not good, why?  You know this means I can't
take them...

> > If this is the case, why not just replacing the define for ACCESS_ONCE()
> > with READ_ONCE() and then go back and just do a search/replace for the
> > whole kernel all at once?
> 
> So that we don't have three variants; the idea is to eventually
> get rid of ACCESS_ONCE entirely.

Then just get rid of it all at once.

thanks,

greg k-h