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

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On 27/11/2020 09:44, Qinglang Miao wrote:
pm_runtime_get_sync will increment pm usage counter even it
failed. Forgetting to putting operation will result in a
reference leak here.

A new function pm_runtime_resume_and_get is introduced in
[0] to keep usage counter balanced. So We fix the reference
leak by replacing it with new funtion.

[0] dd8088d5a896 ("PM: runtime: Add  pm_runtime_resume_and_get to deal with usage counter")

Fixes: f3ba91228e8e ("drm/panfrost: Add initial panfrost driver")
Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
Signed-off-by: Qinglang Miao <miaoqinglang@xxxxxxxxxx>
---
  drivers/gpu/drm/panfrost/panfrost_job.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
index 30e7b7196..04cf3bb67 100644
--- a/drivers/gpu/drm/panfrost/panfrost_job.c
+++ b/drivers/gpu/drm/panfrost/panfrost_job.c
@@ -147,7 +147,7 @@ static void panfrost_job_hw_submit(struct panfrost_job *job, int js)
panfrost_devfreq_record_busy(&pfdev->pfdevfreq); - ret = pm_runtime_get_sync(pfdev->dev);
+	ret = pm_runtime_resume_and_get(pfdev->dev);

Sorry, but in this case this change isn't correct. panfrost_job_hw_submit() is expected to be unbalanced (the PM reference count is expected to be incremented on return).

In the case where pm_runtime_get_sync() fails, the job will eventually timeout, and there's a corresponding pm_runtime_put_noidle() in panfrost_reset().

Potentially this could be handled better (e.g. without waiting for the timeout to occur), but equally this isn't something we expect to happen in normal operation).

Steve

  	if (ret < 0)
  		return;

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