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Date:   Tue, 12 Feb 2019 18:43:54 +0000
From:   Will Deacon <will.deacon@arm.com>
To:     "Paul E. McKenney" <paulmck@linux.ibm.com>
Cc:     linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Andrea Parri <andrea.parri@amarulasolutions.com>,
        Daniel Lustig <dlustig@nvidia.com>,
        David Howells <dhowells@redhat.com>,
        Alan Stern <stern@rowland.harvard.edu>,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [RFC PATCH] docs/memory-barriers.txt: Rewrite "KERNEL I/O
 BARRIER EFFECTS" section
Message-ID: <20190212184354.GC20961@fuggles.cambridge.arm.com>
References: <20190211172948.3322-1-will.deacon@arm.com>
 <20190211202218.GQ4240@linux.ibm.com>
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On Mon, Feb 11, 2019 at 12:22:18PM -0800, Paul E. McKenney wrote:
> On Mon, Feb 11, 2019 at 05:29:48PM +0000, Will Deacon wrote:
> > The "KERNEL I/O BARRIER EFFECTS" section of memory-barriers.txt is vague,
> > x86-centric, out-of-date, incomplete and demonstrably incorrect in places.
> > This is largely because I/O ordering is a horrible can of worms, but also
> > because the document has stagnated as our understanding has evolved.
> > 
> > Attempt to address some of that, by rewriting the section based on
> > recent(-ish) discussions with Arnd, BenH and others. Maybe one day we'll
> > find a way to formalise this stuff, but for now let's at least try to
> > make the English easier to understand.
> > 
> > Cc: "Paul E. McKenney" <paulmck@linux.ibm.com>
> > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> > Cc: Arnd Bergmann <arnd@arndb.de>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Cc: Andrea Parri <andrea.parri@amarulasolutions.com>
> > Cc: Daniel Lustig <dlustig@nvidia.com>
> > Cc: David Howells <dhowells@redhat.com>
> > Cc: Alan Stern <stern@rowland.harvard.edu>
> > cc: Linus Torvalds <torvalds@linux-foundation.org>
> > Signed-off-by: Will Deacon <will.deacon@arm.com>
> 
> Hello, Will,
> 
> The intent is to replace commit 3f305018dcf3 ("docs/memory-barriers.txt:
> Enforce heavy ordering for port I/O accesses"), correct?  Either way is
> fine, just guessing based on the conflicts when applying this one.  ;-)

Yup, I decided to abandon the old patch:

http://lkml.kernel.org/r/20190211153043.GC32385@fuggles.cambridge.arm.com

Thanks,

Will