linux-kernel - [PATCH] dmaengine: imx-sdma: fix deadlock in interrupt handler

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Date:   Thu, 21 Sep 2023 09:57:11 +0000
From:   Tim van der Staaij | Zign <Tim.vanderstaaij@...ngroup.com>
To:     Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>
CC:     Vinod Koul <vkoul@...nel.org>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] dmaengine: imx-sdma: fix deadlock in interrupt handler

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@...ngroup.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);
+
 		sdma_enable_channel(sdmac->sdma, sdmac->channel);
 	}
 }
-- 
2.41.0