From: Navid Emamdoost <navid.emamdoost@gmail.com>
To: Lucas Stach <l.stach@pengutronix.de>
Cc: Qiushi Wu <wu000273@umn.edu>, David Airlie <airlied@linux.ie>,
Andy Shevchenko <andy.shevchenko@gmail.com>,
Kangjie Lu <kjlu@umn.edu>,
etnaviv@lists.freedesktop.org,
dri-devel <dri-devel@lists.freedesktop.org>,
LKML <linux-kernel@vger.kernel.org>,
mccamant@cs.umn.edu, Navid Emamdoost <emamd001@umn.edu>,
Russell King <linux+etnaviv@armlinux.org.uk>
Subject: Re: [PATCH v2] drm/etnaviv: fix ref count leak via pm_runtime_get_sync
Date: Wed, 17 Jun 2020 12:57:09 -0500 [thread overview]
Message-ID: <CAEkB2EQ9DuLt12MXkw3DYpBDaDAxoWTnMC9+=E7v=6dGGRK=nQ@mail.gmail.com> (raw)
In-Reply-To: <befc07e1d630dbc5a6f96fba4e47e083e6386090.camel@pengutronix.de>
Hi Lucas,
On Wed, Jun 17, 2020 at 4:53 AM Lucas Stach <l.stach@pengutronix.de> wrote:
>
> Hi Navid,
>
> Am Montag, den 15.06.2020, 01:12 -0500 schrieb Navid Emamdoost:
> > in etnaviv_gpu_submit, etnaviv_gpu_recover_hang, etnaviv_gpu_debugfs,
> > and etnaviv_gpu_init the call to pm_runtime_get_sync increments the
> > counter even in case of failure, leading to incorrect ref count.
> > In case of failure, decrement the ref count before returning.
>
> While that change is correct with the current API, may I ask the
> question why the way this API works is considered reasonable? A API
> call that fails, but still changes internal state and expects the
> caller to clean up the mess it not really what I would consider fool-
> proof API design. Is there a specific reason why it is done this way
> and not handled internally?
I share the same concern with you on the way this API is working now.
To the best of my knowledge, there are ongoing discussions on this
issue:
https://lkml.org/lkml/2020/6/14/76
https://patchwork.ozlabs.org/project/linux-tegra/patch/20200520095148.10995-1-dinghao.liu@zju.edu.cn/
>
> Regards,
> Lucas
>
> > Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
> > ---
> > Changes in v2:
> > - replace pm_runtime_put with pm_runtime_put_noidle
> > ---
> > drivers/gpu/drm/etnaviv/etnaviv_gpu.c | 14 ++++++++++----
> > 1 file changed, 10 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
> > index a31eeff2b297..7c9f3f9ba123 100644
> > --- a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
> > +++ b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
> > @@ -722,7 +722,7 @@ int etnaviv_gpu_init(struct etnaviv_gpu *gpu)
> > ret = pm_runtime_get_sync(gpu->dev);
> > if (ret < 0) {
> > dev_err(gpu->dev, "Failed to enable GPU power domain\n");
> > - return ret;
> > + goto pm_put;
> > }
> >
> > etnaviv_hw_identify(gpu);
> > @@ -819,6 +819,7 @@ int etnaviv_gpu_init(struct etnaviv_gpu *gpu)
> >
> > fail:
> > pm_runtime_mark_last_busy(gpu->dev);
> > +pm_put:
> > pm_runtime_put_autosuspend(gpu->dev);
> >
> > return ret;
> > @@ -859,7 +860,7 @@ int etnaviv_gpu_debugfs(struct etnaviv_gpu *gpu, struct seq_file *m)
> >
> > ret = pm_runtime_get_sync(gpu->dev);
> > if (ret < 0)
> > - return ret;
> > + goto pm_put;
> >
> > dma_lo = gpu_read(gpu, VIVS_FE_DMA_LOW);
> > dma_hi = gpu_read(gpu, VIVS_FE_DMA_HIGH);
> > @@ -1003,6 +1004,7 @@ int etnaviv_gpu_debugfs(struct etnaviv_gpu *gpu, struct seq_file *m)
> > ret = 0;
> >
> > pm_runtime_mark_last_busy(gpu->dev);
> > +pm_put:
> > pm_runtime_put_autosuspend(gpu->dev);
> >
> > return ret;
> > @@ -1016,7 +1018,7 @@ void etnaviv_gpu_recover_hang(struct etnaviv_gpu *gpu)
> > dev_err(gpu->dev, "recover hung GPU!\n");
> >
> > if (pm_runtime_get_sync(gpu->dev) < 0)
> > - return;
> > + goto pm_put;
> >
> > mutex_lock(&gpu->lock);
> >
> > @@ -1035,6 +1037,7 @@ void etnaviv_gpu_recover_hang(struct etnaviv_gpu *gpu)
> >
> > mutex_unlock(&gpu->lock);
> > pm_runtime_mark_last_busy(gpu->dev);
> > +pm_put:
> > pm_runtime_put_autosuspend(gpu->dev);
> > }
> >
> > @@ -1308,8 +1311,10 @@ struct dma_fence *etnaviv_gpu_submit(struct etnaviv_gem_submit *submit)
> >
> > if (!submit->runtime_resumed) {
> > ret = pm_runtime_get_sync(gpu->dev);
> > - if (ret < 0)
> > + if (ret < 0) {
> > + pm_runtime_put_noidle(gpu->dev);
> > return NULL;
> > + }
> > submit->runtime_resumed = true;
> > }
> >
> > @@ -1326,6 +1331,7 @@ struct dma_fence *etnaviv_gpu_submit(struct etnaviv_gem_submit *submit)
> > ret = event_alloc(gpu, nr_events, event);
> > if (ret) {
> > DRM_ERROR("no free events\n");
> > + pm_runtime_put_noidle(gpu->dev);
> > return NULL;
> > }
> >
>
--
Navid.
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next prev parent reply other threads:[~2020-06-18 7:17 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-14 6:46 [PATCH] drm/etnaviv: fix ref count leak via pm_runtime_get_sync Navid Emamdoost
2020-06-14 9:48 ` Andy Shevchenko
2020-06-15 6:12 ` [PATCH v2] " Navid Emamdoost
2020-06-17 9:53 ` Lucas Stach
2020-06-17 17:57 ` Navid Emamdoost [this message]
2020-06-15 6:13 ` [PATCH] " Navid Emamdoost
2020-06-15 15:57 [PATCH v2] " Markus Elfring
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