Re: [PATCH 5/5] mmc: cavium: Fix probing race with regulator

[Jan Glauber]

On Tue, May 16, 2017 at 09:37:48AM -0500, Rob Herring wrote:
> On Tue, May 16, 2017 at 8:38 AM, Jan Glauber
> <jan.glauber@xxxxxxxxxxxxxxxxxx> wrote:
> > On Tue, May 16, 2017 at 08:07:50AM -0500, Rob Herring wrote:
> >> On Tue, May 16, 2017 at 4:36 AM, Jan Glauber <jglauber@xxxxxxxxxx> wrote:
> >> > If the regulator probing is not yet finished this driver
> >> > might catch a -EPROBE_DEFER. Returning after this condition
> >> > did not remove the created platform device. On a repeated
> >> > call to the probe function the of_platform_device_create
> >> > fails.
> >> >
> >> > Calling of_platform_device_destroy after EPROBE_DEFER resolves
> >> > this bug.
> >> >
> >> > Signed-off-by: Jan Glauber <jglauber@xxxxxxxxxx>
> >> > ---
> >> >  drivers/mmc/host/cavium-thunderx.c | 4 +++-
> >> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >> >
> >> > diff --git a/drivers/mmc/host/cavium-thunderx.c b/drivers/mmc/host/cavium-thunderx.c
> >> > index fe3d772..257535e 100644
> >> > --- a/drivers/mmc/host/cavium-thunderx.c
> >> > +++ b/drivers/mmc/host/cavium-thunderx.c
> >> > @@ -137,8 +137,10 @@ static int thunder_mmc_probe(struct pci_dev *pdev,
> >> >                                 continue;
> >> >
> >> >                         ret = cvm_mmc_of_slot_probe(&host->slot_pdev[i]->dev, host);
> >> > -                       if (ret)
> >> > +                       if (ret) {
> >> > +                               of_platform_device_destroy(&host->slot_pdev[i]->dev, NULL);
> >>
> >> What if this fails after the 1st iteration of the loop. It's only
> >> cleaning up the current device.
> >
> > The platform device is just a dummy device created directly before
> > cvm_mmc_of_slot_probe(). So there is no need to cleanup anything else.
> 
> So if you have 2 slots, the first slot probes successfully and the 2nd
> slot defers, then you only need to clean-up the 2nd device/slot? Looks
> to me like you are leaking the 1st device you alloc.

OK, got it now. My assumption was that your scenario can't happen in
reality with EPROBE_DEFER.

> >
> > As far as I've seen it the platform code 'tags' the nodes it already
> > used, but I need the same node to be parsed again on -EPROBE_DEFER.
> >
> >> Use devm_of_platform_populate or
> >> of_platform_populate/of_platform_depopulate instead.
> >
> > I'm not sure one of these will work here.
> 
> Those functions loop over child nodes and create devices. You are
> doing the same thing. You'd just need to create all the devices first
> and then probe them all.

I'll take a look at devm_of_platform_populate then. If I can use it it
will solve the leak issue.

thanks,
Jan

> The whole structure here with the dummy devices and how you are
> initializing things is screwy. IMO, you should be creating actual
> drivers for the dummy devices.
> 
> Rob