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Date:   Wed, 4 Jan 2023 09:28:50 +0100
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Deepak R Varma <drv@mailo.com>
Cc:     Jiri Slaby <jirislaby@kernel.org>,
        "Maciej W. Rozycki" <macro@orcam.me.uk>,
        linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
        Saurabh Singh Sengar <ssengar@microsoft.com>,
        Praveen Kumar <kumarpraveen@linux.microsoft.com>
Subject: Re: [PATCH v4 2/2] tty: serial: dz: convert atomic_* to refcount_*
 APIs for irq_guard
Message-ID: <Y7U4wiLM/z+H/rOc@kroah.com>
References: <cover.1671898144.git.drv@mailo.com>
 <51ef854f77779c82010379420139993e12c38776.1671898144.git.drv@mailo.com>
 <3c4e744f-c313-e195-af93-a22382c81bb6@kernel.org>
 <Y7P+zZEF09YWs5yW@qemulion>
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On Tue, Jan 03, 2023 at 03:39:17PM +0530, Deepak R Varma wrote:
> On Tue, Jan 03, 2023 at 10:00:48AM +0100, Jiri Slaby wrote:
> > On 26. 12. 22, 7:21, Deepak R Varma wrote:
> > > The refcount_* APIs are designed to address known issues with the
> > > atomic_t APIs for reference counting. They provide following distinct
> > > advantages:
> > >     - protect the reference counters from overflow/underflow
> > >     - avoid use-after-free errors
> > >     - provide improved memory ordering guarantee schemes
> > >     - neater and safer.
> > > Hence, replace the atomic_* APIs by their equivalent refcount_t
> > > API functions.
> > >
> > > This patch proposal address the following warnings generated by
> > > the atomic_as_refcounter.cocci coccinelle script
> > > atomic_add_return(-1, ...)
> > ...
> > > --- a/drivers/tty/serial/dz.c
> > > +++ b/drivers/tty/serial/dz.c
> > ...
> > > @@ -400,18 +399,16 @@ static int dz_startup(struct uart_port *uport)
> > >   	struct dz_port *dport = to_dport(uport);
> > >   	struct dz_mux *mux = dport->mux;
> > >   	unsigned long flags;
> > > -	int irq_guard;
> > >   	int ret;
> > >   	u16 tmp;
> > >
> > > -	irq_guard = atomic_add_return(1, &mux->irq_guard);
> > > -	if (irq_guard != 1)
> > > +	refcount_inc(&mux->irq_guard);
> > > +	if (refcount_read(&mux->irq_guard) != 1)
> > >   		return 0;
> > >
> > > -	ret = request_irq(dport->port.irq, dz_interrupt,
> > > -			  IRQF_SHARED, "dz", mux);
> > > +	ret = request_irq(dport->port.irq, dz_interrupt, IRQF_SHARED, "dz", mux);
> >
> > How is this related to the above described change?
> 
> No, it is not. My apologies. I must have joined the lines for improved readability
> and forgot to revert. I will restore this in next revision based on the feedback
> on the other patch of this series. OR I can include this change in the current
> change log as a "while at it..." statement. Would you advise me?

NEVER have a "while at it..." change as part of a commit unless it is
relevant to the main change being made.  You know better...

thanks,

greg k-h