linux-kernel - RE: [PATCH v5] locking/memory-barriers.txt: Improve documentation for writel() example

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Message-ID: <PH0PR12MB548171D8D6271B88FF27D156DC329@PH0PR12MB5481.namprd12.prod.outlook.com>
Date:   Fri, 28 Oct 2022 17:59:50 +0000
From:   Parav Pandit <parav@...dia.com>
To:     "paulmck@...nel.org" <paulmck@...nel.org>
CC:     "bagasdotme@...il.com" <bagasdotme@...il.com>,
        "arnd@...db.de" <arnd@...db.de>,
        "stern@...land.harvard.edu" <stern@...land.harvard.edu>,
        "parri.andrea@...il.com" <parri.andrea@...il.com>,
        "will@...nel.org" <will@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "boqun.feng@...il.com" <boqun.feng@...il.com>,
        "npiggin@...il.com" <npiggin@...il.com>,
        "dhowells@...hat.com" <dhowells@...hat.com>,
        "j.alglave@....ac.uk" <j.alglave@....ac.uk>,
        "luc.maranget@...ia.fr" <luc.maranget@...ia.fr>,
        "akiyks@...il.com" <akiyks@...il.com>,
        Dan Lustig <dlustig@...dia.com>,
        "joel@...lfernandes.org" <joel@...lfernandes.org>,
        "corbet@....net" <corbet@....net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: RE: [PATCH v5] locking/memory-barriers.txt: Improve documentation for
 writel() example

Hi Will, Paul,

> From: Paul E. McKenney <paulmck@...nel.org>
> Sent: Friday, October 28, 2022 1:56 PM
> 
> On Thu, Oct 27, 2022 at 11:10:00PM +0300, Parav Pandit wrote:
> > The cited commit describes that when using writel(), explicit wmb() is
> > not needed. wmb() is an expensive barrier. writel() uses the needed
> > platform specific barrier instead of wmb().
> >
> > writeX() section of "KERNEL I/O BARRIER EFFECTS" already describes
> > ordering of I/O accessors with MMIO writes.
> >
> > Hence add the comment for pseudo code of writel() and remove confusing
> > text around writel() and wmb().
> >
> > commit 5846581e3563 ("locking/memory-barriers.txt: Fix broken DMA vs.
> > MMIO ordering example")
> >
> > Signed-off-by: Parav Pandit <parav@...dia.com>
> 
> Hearing no immediate objections, I have pulled this in for further review.  If
> all goes well, I intend to submit this during the upcoming
> v6.2 merge window.
> 
> 							Thanx, Paul

I have taken Will's email patch suggestion with small editorial modification in it.
But I was afraid to add his Signed-off-by myself in v5 without consulting him.

Will,
Can you please reply to add your Signed-off-by as well or not?