linux-kernel - Re: [PATCH] dmaengine: rcar-dmac: Fix PM usage counter imbalance

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Message-ID: <CAMuHMdUhZqLCkLWtFTaCq67=Nb0O0_XLSWeyweMiNp25XArfKA@mail.gmail.com>
Date: Wed, 2 Jul 2025 12:18:55 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Zhang Shurong <zhang_shurong@...mail.com>
Cc: vkoul@...nel.org, magnus.damm@...il.com, robin.murphy@....com, 
	ulf.hansson@...aro.org, kuninori.morimoto.gx@...esas.com, 
	u.kleine-koenig@...libre.com, dmaengine@...r.kernel.org, 
	linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>
Subject: Re: [PATCH] dmaengine: rcar-dmac: Fix PM usage counter imbalance

Hi Zhang,

On Sun, 29 Jun 2025 at 17:57, Zhang Shurong <zhang_shurong@...mail.com> wrote:
> 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 by replacing
> it with pm_runtime_resume_and_get to keep usage counter
> balanced.
>
> Fixes: 87244fe5abdf ("dmaengine: rcar-dmac: Add Renesas R-Car Gen2 DMA Controller (DMAC) driver")
> Signed-off-by: Zhang Shurong <zhang_shurong@...mail.com>

Thanks for your patch!

Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>

> --- a/drivers/dma/sh/rcar-dmac.c
> +++ b/drivers/dma/sh/rcar-dmac.c
> @@ -1068,7 +1068,7 @@ static int rcar_dmac_alloc_chan_resources(struct dma_chan *chan)
>         if (ret < 0)
>                 return -ENOMEM;
>
> -       return pm_runtime_get_sync(chan->device->dev);
> +       return pm_runtime_resume_and_get(chan->device->dev);

Note that there are other issues with this function: in case of failure,
none of the memory allocated before is freed.  Probably the original
author assumed none of this can really fail.

>  }
>
>  static void rcar_dmac_free_chan_resources(struct dma_chan *chan)

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds