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

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Message-ID: <20210607180434.GC40811@e120937-lin>
Date:   Mon, 7 Jun 2021 19:04:34 +0100
From:   Cristian Marussi <cristian.marussi@....com>
To:     Sudeep Holla <sudeep.holla@....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

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.

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().

Thanks,
Cristian

> --
> Regards,
> Sudeep