linux-kernel - Re: drivers/dma/xilinx/xilinx_dpdma.c:1172 xilinx_dpdma_synchronize() error: double unlocked 'chan->vchan.lock' (orig line 1170)

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Message-ID: <20200811225006.GF17446@pendragon.ideasonboard.com>
Date:   Wed, 12 Aug 2020 01:50:06 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     kernel test robot <lkp@...el.com>
Cc:     Hyun Kwon <hyun.kwon@...inx.com>, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org, Vinod Koul <vkoul@...nel.org>,
        Tejas Upadhyay <tejasu@...inx.com>,
        Michal Simek <monstr@...str.eu>
Subject: Re: drivers/dma/xilinx/xilinx_dpdma.c:1172
 xilinx_dpdma_synchronize() error: double unlocked 'chan->vchan.lock' (orig
 line 1170)

On Wed, Aug 12, 2020 at 06:37:59AM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   c636eef2ee3696f261a35f34989842701a107895
> commit: 7cbb0c63de3fc218fd06ecfedb477772a4d12f76 dmaengine: xilinx: dpdma: Add the Xilinx DisplayPort DMA engine driver
> date:   4 weeks ago
> config: h8300-randconfig-m031-20200811 (attached as .config)
> compiler: h8300-linux-gcc (GCC) 9.3.0
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@...el.com>
> 
> smatch warnings:
> drivers/dma/xilinx/xilinx_dpdma.c:1172 xilinx_dpdma_synchronize() error: double unlocked 'chan->vchan.lock' (orig line 1170)

Unless I'm mistaken, this is a false positive. I'd appreciate if someone
could check if I'm missing something obvious.

> vim +1172 drivers/dma/xilinx/xilinx_dpdma.c
> 
>   1140	
>   1141	/**
>   1142	 * xilinx_dpdma_synchronize - Synchronize callback execution
>   1143	 * @dchan: DMA channel
>   1144	 *
>   1145	 * Synchronizing callback execution ensures that all previously issued
>   1146	 * transfers have completed and all associated callbacks have been called and
>   1147	 * have returned.
>   1148	 *
>   1149	 * This function waits for the DMA channel to stop. It assumes it has been
>   1150	 * paused by a previous call to dmaengine_terminate_async(), and that no new
>   1151	 * pending descriptors have been issued with dma_async_issue_pending(). The
>   1152	 * behaviour is undefined otherwise.
>   1153	 */
>   1154	static void xilinx_dpdma_synchronize(struct dma_chan *dchan)
>   1155	{
>   1156		struct xilinx_dpdma_chan *chan = to_xilinx_chan(dchan);
>   1157		unsigned long flags;
>   1158	
>   1159		xilinx_dpdma_chan_stop(chan);
>   1160	
>   1161		spin_lock_irqsave(&chan->vchan.lock, flags);
>   1162		if (chan->desc.pending) {
>   1163			vchan_terminate_vdesc(&chan->desc.pending->vdesc);
>   1164			chan->desc.pending = NULL;
>   1165		}
>   1166		if (chan->desc.active) {
>   1167			vchan_terminate_vdesc(&chan->desc.active->vdesc);
>   1168			chan->desc.active = NULL;
>   1169		}
> > 1170		spin_unlock_irqrestore(&chan->vchan.lock, flags);
>   1171	
> > 1172		vchan_synchronize(&chan->vchan);
>   1173	}
>   1174	
> 

-- 
Regards,

Laurent Pinchart