Re: [PATCH] drm/panfrost: fix ref count leak in panfrost_job_hw_submit

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On 09/07/2020 16:44, Rob Herring wrote:
On Sun, Jun 14, 2020 at 12:27 AM Navid Emamdoost
<navid.emamdoost@xxxxxxxxx> wrote:

in panfrost_job_hw_submit, pm_runtime_get_sync is called which
increments the counter even in case of failure, leading to incorrect
ref count. In case of failure, decrement the ref count before returning.

Signed-off-by: Navid Emamdoost <navid.emamdoost@xxxxxxxxx>
---
  drivers/gpu/drm/panfrost/panfrost_job.c | 8 +++++---
  1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
index 7914b1570841..89ac84667eb1 100644
--- a/drivers/gpu/drm/panfrost/panfrost_job.c
+++ b/drivers/gpu/drm/panfrost/panfrost_job.c
@@ -147,11 +147,10 @@ static void panfrost_job_hw_submit(struct panfrost_job *job, int js)

         ret = pm_runtime_get_sync(pfdev->dev);
         if (ret < 0)
-               return;
+               goto out;

If the get failed, I don't think we want to do a put.

The pm_runtime_get_sync() does actually always increment the reference (even when returning a failure), but actually I don't think we want it here anyway, as I think I explained before[1]. [1] https://lore.kernel.org/dri-devel/272650ba-2c44-9084-7829-b04023eba723@xxxxxxx


         if (WARN_ON(job_read(pfdev, JS_COMMAND_NEXT(js)))) {
-               pm_runtime_put_sync_autosuspend(pfdev->dev);

This is a correct change - we don't want the put here. (Although this should never happen).

-               return;
+               goto out;
         }

         cfg = panfrost_mmu_as_get(pfdev, &job->file_priv->mmu);
@@ -184,6 +183,9 @@ static void panfrost_job_hw_submit(struct panfrost_job *job, int js)
                                 job, js, jc_head);

         job_write(pfdev, JS_COMMAND_NEXT(js), JS_COMMAND_START);

So we start the job here and then...

+out:
+       pm_runtime_put_sync_autosuspend(pfdev->dev);

...turn off clocks/power here. Typically, you'd be fine as autosuspend
has a delay by default, but userspace is free to change the delay to
0.

+       return;

A return at the end of the function with no argument is pointless.

Steve

  }

  static void panfrost_acquire_object_fences(struct drm_gem_object **bos,
--
2.17.1


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