linux-kernel - Re: [PATCH 5.4 160/344] dmaengine: imx-sdma: Fix memory leak

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Message-ID: <20200224212319.GE26320@sasha-vm>
Date:   Mon, 24 Feb 2020 16:23:19 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     Sascha Hauer <s.hauer@...gutronix.de>
Cc:     Andreas Tobler <andreas.tobler@...ay.ch>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Robin Gong <yibin.gong@....com>, Vinod Koul <vkoul@...nel.org>
Subject: Re: [PATCH 5.4 160/344] dmaengine: imx-sdma: Fix memory leak

On Mon, Feb 24, 2020 at 03:57:18PM +0100, Sascha Hauer wrote:
>On Mon, Feb 24, 2020 at 01:24:04PM +0000, Andreas Tobler wrote:
>> Hi all,
>>
>> On 21.02.20 08:39, Greg Kroah-Hartman wrote:
>> > From: Sascha Hauer <s.hauer@...gutronix.de>
>> >
>> > [ Upstream commit 02939cd167095f16328a1bd5cab5a90b550606df ]
>> >
>> > The current descriptor is not on any list of the virtual DMA channel.
>> > Once sdma_terminate_all() is called when a descriptor is currently
>> > in flight then this one is forgotten to be freed. We have to call
>> > vchan_terminate_vdesc() on this descriptor to re-add it to the lists.
>> > Now that we also free the currently running descriptor we can (and
>> > actually have to) remove the current descriptor from its list also
>> > for the cyclic case.
>> >
>> > Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de>
>> > Reviewed-by: Robin Gong <yibin.gong@....com>
>> > Tested-by: Robin Gong <yibin.gong@....com>
>> > Link: https://lore.kernel.org/r/20191216105328.15198-10-s.hauer@pengutronix.de
>> > Signed-off-by: Vinod Koul <vkoul@...nel.org>
>> > Signed-off-by: Sasha Levin <sashal@...nel.org>
>> > ---
>> >   drivers/dma/imx-sdma.c | 19 +++++++++++--------
>> >   1 file changed, 11 insertions(+), 8 deletions(-)
>> >
>> > diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
>> > index c27e206a764c3..66f1b2ac5cde4 100644
>> > --- a/drivers/dma/imx-sdma.c
>> > +++ b/drivers/dma/imx-sdma.c
>> > @@ -760,12 +760,8 @@ static void sdma_start_desc(struct sdma_channel *sdmac)
>> >   		return;
>> >   	}
>> >   	sdmac->desc = desc = to_sdma_desc(&vd->tx);
>> > -	/*
>> > -	 * Do not delete the node in desc_issued list in cyclic mode, otherwise
>> > -	 * the desc allocated will never be freed in vchan_dma_desc_free_list
>> > -	 */
>> > -	if (!(sdmac->flags & IMX_DMA_SG_LOOP))
>> > -		list_del(&vd->node);
>> > +
>> > +	list_del(&vd->node);
>> >
>> >   	sdma->channel_control[channel].base_bd_ptr = desc->bd_phys;
>> >   	sdma->channel_control[channel].current_bd_ptr = desc->bd_phys;
>> > @@ -1071,7 +1067,6 @@ static void sdma_channel_terminate_work(struct work_struct *work)
>> >
>> >   	spin_lock_irqsave(&sdmac->vc.lock, flags);
>> >   	vchan_get_all_descriptors(&sdmac->vc, &head);
>> > -	sdmac->desc = NULL;
>> >   	spin_unlock_irqrestore(&sdmac->vc.lock, flags);
>> >   	vchan_dma_desc_free_list(&sdmac->vc, &head);
>> >   	sdmac->context_loaded = false;
>> > @@ -1080,11 +1075,19 @@ static void sdma_channel_terminate_work(struct work_struct *work)
>> >   static int sdma_disable_channel_async(struct dma_chan *chan)
>> >   {
>> >   	struct sdma_channel *sdmac = to_sdma_chan(chan);
>> > +	unsigned long flags;
>> > +
>> > +	spin_lock_irqsave(&sdmac->vc.lock, flags);
>> >
>> >   	sdma_disable_channel(chan);
>> >
>> > -	if (sdmac->desc)
>> > +	if (sdmac->desc) {
>> > +		vchan_terminate_vdesc(&sdmac->desc->vd);
>> > +		sdmac->desc = NULL;
>> >   		schedule_work(&sdmac->terminate_worker);
>> > +	}
>> > +
>> > +	spin_unlock_irqrestore(&sdmac->vc.lock, flags);
>> >
>> >   	return 0;
>> >   }
>> >
>>
>> This patch breaks our imx6 board with the attached trace.  Reverting the
>> patch makes it boot again.
>> I tried also 5.6-rc3 and it booted too. A closer look into imx-sdma.c
>> from 5.6-rc3 showed me some details which might have to be backported as
>> well to make this patch work.
>> I tried a1ff6a07f5a3951fcac84f064a76d1ad79c10e40 and was somehow
>> successful. I still have one trace but the board boots now.
>>
>> Any insights from the experts?
>
>This series should be applied as a whole or not, only 7/9 is optional.
>
>It seems I have to avoid the trigger word "fix" in my commit messages or
>make sure these patches won't apply without their dependencies :-/

Or you could just tag the dependencies so that we could take all of them
as well? We have a nice "Depends-on:" tag that makes it easy.

As with everything in life, you want to communicate more effectively
rather than not communicate at all.

-- 
Thanks,
Sasha