From: Sascha Hauer <s.hauer@pengutronix.de>
To: Tim van der Staaij | Zign <Tim.vanderstaaij@zigngroup.com>
Cc: Shawn Guo <shawnguo@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Vinod Koul <vkoul@kernel.org>,
Pengutronix Kernel Team <kernel@pengutronix.de>,
"dmaengine@vger.kernel.org" <dmaengine@vger.kernel.org>,
Fabio Estevam <festevam@gmail.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] dmaengine: imx-sdma: fix deadlock in interrupt handler
Date: Fri, 22 Sep 2023 11:50:32 +0200 [thread overview]
Message-ID: <20230922095032.GU637806@pengutronix.de> (raw)
In-Reply-To: <AM0PR08MB30897429213E8DB9BCC1D6C880F8A@AM0PR08MB3089.eurprd08.prod.outlook.com>
Hi Tim,
On Thu, Sep 21, 2023 at 09:57:11AM +0000, Tim van der Staaij | Zign wrote:
> dev_warn internally acquires the lock that is already held when
> sdma_update_channel_loop is called. Therefore it is acquired twice and
> this is detected as a deadlock. Temporarily release the lock while
> logging to avoid this.
>
> Signed-off-by: Tim van der Staaij <tim.vanderstaaij@zigngroup.com>
> Link: https://lore.kernel.org/all/AM0PR08MB308979EC3A8A53AE6E2D3408802CA@AM0PR08MB3089.eurprd08.prod.outlook.com/
> ---
> drivers/dma/imx-sdma.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
> index 51012bd39900..3a7cd783a567 100644
> --- a/drivers/dma/imx-sdma.c
> +++ b/drivers/dma/imx-sdma.c
> @@ -904,7 +904,10 @@ static void sdma_update_channel_loop(struct sdma_channel *sdmac)
> * owned buffer is available (i.e. BD_DONE was set too late).
> */
> if (sdmac->desc && !is_sdma_channel_enabled(sdmac->sdma, sdmac->channel)) {
> + spin_unlock(&sdmac->vc.lock);
> dev_warn(sdmac->sdma->dev, "restart cyclic channel %d\n", sdmac->channel);
> + spin_lock(&sdmac->vc.lock);
This is strange. Why and how does dev_warn() call back into the SDMA
driver?
We shouldn't merge this without having a clue what exactly goes wrong
here. Please provide the corresponding lockdep output.
Sascha
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next prev parent reply other threads:[~2023-09-22 9:51 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-21 9:57 [PATCH] dmaengine: imx-sdma: fix deadlock in interrupt handler Tim van der Staaij | Zign
2023-09-21 18:55 ` Fabio Estevam
2023-09-22 9:50 ` Sascha Hauer [this message]
2023-09-25 9:05 ` Sascha Hauer
2023-09-26 7:54 ` Tim van der Staaij | Zign
2023-09-25 9:20 ` Uwe Kleine-König
2023-09-25 9:27 ` Sascha Hauer
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