Re: [PATCH 5.10 14/86] dmaengine: mediatek:Fix PM usage reference leak of mtk_uart_apdma_alloc_chan_resources

Pavel Machek
2022-04-27T20:28:44Z

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Hi!

> pm_runtime_get_sync will increment pm usage counter even it failed.
> Forgetting to putting operation will result in reference leak here.
> We fix it:
> 1) Replacing it with pm_runtime_resume_and_get to keep usage counter
> balanced.

Suspect.

> 2) Add putting operation before returning error.

Yes but you also put in success case, which is likely
wrong. mtk_uart_apdma_free_chan_resources() does second put.

> +++ b/drivers/dma/mediatek/mtk-uart-apdma.c
> @@ -274,7 +274,7 @@ static int mtk_uart_apdma_alloc_chan_resources(struct dma_chan *chan)
> unsigned int status;
> int ret;
>
> - ret = pm_runtime_get_sync(mtkd->ddev.dev);
> + ret = pm_runtime_resume_and_get(mtkd->ddev.dev);
> if (ret < 0) {
> pm_runtime_put_noidle(chan->device->dev);
> return ret;

This is suspect, too. What is the put_noidle doing there? Seems like
it was meant to undo the get_sync operation, but uses different
argument?

> @@ -288,18 +288,21 @@ static int mtk_uart_apdma_alloc_chan_resources(struct dma_chan *chan)
>
> if (mtkd->support_33bits)
> mtk_uart_apdma_write(c, VFF_4G_SUPPORT, VFF_4G_SUPPORT_CLR_B);
>
> +err_pm:
> + pm_runtime_put_noidle(mtkd->ddev.dev);
> return ret;
> }

This should only be done in error case.

Best regards,
Pavel
--
People of Russia, stop Putin before his war on Ukraine escalates.

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