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

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Message-ID: <20161120093932.GA21152@kroah.com>
Date:   Sun, 20 Nov 2016 10:39:32 +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 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 :(

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?

Or just send Linus a patch for this all at once after -rc1 is out?

thanks,

greg k-h