linux-kernel - Re: [RFC PATCH 02/10] firmware: arm_scmi: Add missing xfer reinit

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Message-ID: <20210607182924.yauvg4zli6gmulev@bogus>
Date:   Mon, 7 Jun 2021 19:30:30 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Cristian Marussi <cristian.marussi@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        james.quinlan@...adcom.com, Jonathan.Cameron@...wei.com,
        f.fainelli@...il.com, etienne.carriere@...aro.org,
        vincent.guittot@...aro.org, souvik.chakravarty@....com
Subject: Re: [RFC PATCH 02/10] firmware: arm_scmi: Add missing xfer
 reinit_completion

On Mon, Jun 07, 2021 at 07:04:34PM +0100, Cristian Marussi wrote:
> Hi,
> 
> On Mon, Jun 07, 2021 at 06:42:57PM +0100, Sudeep Holla wrote:
> > On Sun, Jun 06, 2021 at 11:12:24PM +0100, Cristian Marussi wrote:
> > > Reusing timed out xfers in a loop can lead to issue if completion was not
> > > properly reinitialized.
> > >
> > > Signed-off-by: Cristian Marussi <cristian.marussi@....com>
> > > ---
> > >  drivers/firmware/arm_scmi/driver.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > >
> > > diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
> > > index bee33f9c2032..759ae4a23e74 100644
> > > --- a/drivers/firmware/arm_scmi/driver.c
> > > +++ b/drivers/firmware/arm_scmi/driver.c
> > > @@ -448,6 +448,7 @@ static int do_xfer(const struct scmi_protocol_handle *ph,
> > >  			      xfer->hdr.poll_completion);
> > >
> > >  	xfer->hdr.status = SCMI_SUCCESS;
> > > +	reinit_completion(&xfer->done);
> > >
> > 
> > What could happen after xfer_get_init->scmi_xfer_get->reinit_completion
> > that it needs to be re-initialised again. I don't see any reason for this ?
> > If there are, please state them explicitly. If this is needed, I would drop
> > the one in scmi_xfer_get().
> > 
> 
> The reason, like I explained in the other reply in hdr.status, is the
> possibility of do_xfer loops and being more defensive.
>

Understood.

> I agree that if what I blabbed in the other email is acceptable, I could
> drop the reinit_completion in xfer_get() and just use it before
> send_message().
>

I wonder if it is possible to reset only on error if possible and not
expensive of-course ?

--
Regards,
Sudeep