linux-kernel - Re: [PATCH v2 01/21] docs/memory-barriers.txt: Rewrite "KERNEL I/O BARRIER EFFECTS" section

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Message-ID: <e172bf1d741eafd8c056ae3692b400f24bb7c3a7.camel@kernel.crashing.org>
Date:   Fri, 12 Apr 2019 12:07:09 +1000
From:   Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Will Deacon <will.deacon@....com>,
        linux-arch <linux-arch@...r.kernel.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        "Paul E. McKenney" <paulmck@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Arnd Bergmann <arnd@...db.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrea Parri <andrea.parri@...rulasolutions.com>,
        Palmer Dabbelt <palmer@...ive.com>,
        Daniel Lustig <dlustig@...dia.com>,
        David Howells <dhowells@...hat.com>,
        Alan Stern <stern@...land.harvard.edu>,
        "Maciej W. Rozycki" <macro@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        Ingo Molnar <mingo@...nel.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>, Tony Luck <tony.luck@...el.com>,
        Mikulas Patocka <mpatocka@...hat.com>,
        Akira Yokosawa <akiyks@...il.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Nicholas Piggin <npiggin@...il.com>
Subject: Re: [PATCH v2 01/21] docs/memory-barriers.txt: Rewrite "KERNEL I/O
 BARRIER EFFECTS" section

On Thu, 2019-04-11 at 15:34 -0700, Linus Torvalds wrote:
> On Thu, Apr 11, 2019 at 3:13 PM Benjamin Herrenschmidt
> <benh@...nel.crashing.org> wrote:
> > 
> > Minor nit... I would have said "All readX() and writeX() accesses
> > _from
> > the same CPU_ to the same peripheral... and then s/the CPU/this
> > CPU.
> 
> Maybe talk about "same thread" rather than "same cpu", with the
> understanding that scheduling/preemption has to include the
> appropriate cross-CPU IO barrier?

Works for me, but why not spell all this out in the document ? We know,
but others might not.

Cheers,
Ben.