linux-kernel - Re: [RFC PATCH 02/57] drivers: ipmi: Drop device reference

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Message-ID: <20190603195927.GN2742@minyard.net>
Date:   Mon, 3 Jun 2019 14:59:27 -0500
From:   Corey Minyard <minyard@....org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Suzuki K Poulose <suzuki.poulose@....com>,
        linux-kernel@...r.kernel.org, rafael@...nel.org,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [RFC PATCH 02/57] drivers: ipmi: Drop device reference

On Mon, Jun 03, 2019 at 09:09:21PM +0200, Greg KH wrote:
> On Mon, Jun 03, 2019 at 04:49:28PM +0100, Suzuki K Poulose wrote:
> > Drop the reference to a device found via bus_find_device()
> > 
> > Cc: Corey Minyard <minyard@....org>
> > Cc: Arnd Bergmann <arnd@...db.de>
> > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> > ---
> >  drivers/char/ipmi/ipmi_si_platform.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/drivers/char/ipmi/ipmi_si_platform.c b/drivers/char/ipmi/ipmi_si_platform.c
> > index f2a91c4..ff82353 100644
> > --- a/drivers/char/ipmi/ipmi_si_platform.c
> > +++ b/drivers/char/ipmi/ipmi_si_platform.c
> > @@ -442,6 +442,7 @@ void ipmi_remove_platform_device_by_name(char *name)
> >  				      pdev_match_name))) {
> >  		struct platform_device *pdev = to_platform_device(dev);
> >  
> > +		put_device(dev);
> >  		platform_device_unregister(pdev);
> 
> So you drop the reference, and then actually use the pointer?

I did think about this, and in this case you can, I think.
platform_device_unregister() does a put_device() at the end of it's
processing, right?

But it is better style to do it the other way, so I can change it.

-corey

> 
> The drop needs to be _after_ the call to platform_device_unregister().
> 
> thanks,
> 
> greg k-h