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SubjectRe: [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@huawei.com>
> Signed-off-by: Qinglang Miao <miaoqinglang@huawei.com>
> ---
> 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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