From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: devel@driverdev.osuosl.org, Len Brown <len.brown@intel.com>,
Pavel Machek <pavel@ucw.cz>,
linux-pm@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
kjlu@umn.edu, linux-kernel@vger.kernel.org,
Jonathan Hunter <jonathanh@nvidia.com>,
Thierry Reding <thierry.reding@gmail.com>,
Dinghao Liu <dinghao.liu@zju.edu.cn>,
linux-tegra@vger.kernel.org, Dmitry Osipenko <digetx@gmail.com>,
Mauro Carvalho Chehab <mchehab@kernel.org>,
linux-media@vger.kernel.org
Subject: Re: [PATCH] media: staging: tegra-vde: fix runtime pm imbalance on error
Date: Thu, 21 May 2020 19:02:23 +0200 [thread overview]
Message-ID: <7515020.pTbQcekcxr@kreacher> (raw)
In-Reply-To: <20200520150230.GC30374@kadam>
On Wednesday, May 20, 2020 5:02:30 PM CEST Dan Carpenter wrote:
> On Wed, May 20, 2020 at 01:15:44PM +0300, Dmitry Osipenko wrote:
> > 20.05.2020 12:51, Dinghao Liu пишет:
> > > pm_runtime_get_sync() increments the runtime PM usage counter even
> > > it returns an error code. Thus a pairing decrement is needed on
> > > the error handling path to keep the counter balanced.
> > >
> > > Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
> > > ---
> > > drivers/staging/media/tegra-vde/vde.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/staging/media/tegra-vde/vde.c b/drivers/staging/media/tegra-vde/vde.c
> > > index d3e63512a765..dd134a3a15c7 100644
> > > --- a/drivers/staging/media/tegra-vde/vde.c
> > > +++ b/drivers/staging/media/tegra-vde/vde.c
> > > @@ -777,7 +777,7 @@ static int tegra_vde_ioctl_decode_h264(struct tegra_vde *vde,
> > >
> > > ret = pm_runtime_get_sync(dev);
> > > if (ret < 0)
> > > - goto unlock;
> > > + goto put_runtime_pm;
> > >
> > > /*
> > > * We rely on the VDE registers reset value, otherwise VDE
> > >
> >
> > Hello Dinghao,
> >
> > Thank you for the patch. I sent out a similar patch a week ago [1].
> >
> > [1]
> > https://patchwork.ozlabs.org/project/linux-tegra/patch/20200514210847.9269-2-digetx@gmail.com/
> >
> > The pm_runtime_put_noidle() should have the same effect as yours
> > variant, although my variant won't change the last_busy RPM time, which
> > I think is a bit more appropriate behavior.
>
> I don't think either patch is correct. The right thing to do is to fix
> __pm_runtime_resume() so it doesn't leak a reference count on error.
>
> The problem is that a lot of functions don't check the return so
> possibly we are relying on that behavior.
Actually, the function was written with this case in mind.
In retrospect, that has been a mistake and there should be a void variant
to cover this case, but it's been like that for several years and the
documentation doesn't really say that the reference counter will be
decremented on errors.
> We may need to introduce a
> new function which cleans up properly instead of leaking reference
> counts?
Well, even with that, all of the broken callers of pm_runtime_get_sync()
would need to be changed to use the new function instead?
Is that what you mean?
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next prev parent reply other threads:[~2020-05-21 17:02 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-20 9:51 [PATCH] media: staging: tegra-vde: fix runtime pm imbalance on error Dinghao Liu
2020-05-20 10:15 ` Dmitry Osipenko
2020-05-20 15:02 ` Dan Carpenter
2020-05-21 3:42 ` dinghao.liu
2020-05-21 9:15 ` Dan Carpenter
2020-05-21 15:22 ` Rafael J. Wysocki
2020-05-21 17:39 ` Dan Carpenter
2020-05-22 13:10 ` Thierry Reding
2020-05-22 13:23 ` Dan Carpenter
2020-05-22 14:43 ` Thierry Reding
2020-05-28 12:08 ` Dan Carpenter
2020-05-28 12:31 ` Rafael J. Wysocki
2020-05-21 17:02 ` Rafael J. Wysocki [this message]
2020-05-20 20:15 ` kbuild test robot
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