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SubjectRe: [PATCH v2] drm/etnaviv: fix ref count leak via pm_runtime_get_sync
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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?

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;
> }
>

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