linux-kernel - [PATCH AUTOSEL 5.0 76/99] dmaengine: bcm2835: Avoid GFP_KERNEL in device_prep_slave

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Message-Id: <20190507053235.29900-76-sashal@kernel.org>
Date:   Tue,  7 May 2019 01:32:10 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Stefan Wahren <stefan.wahren@...e.com>,
        Aaro Koskinen <aaro.koskinen@....fi>,
        Vinod Koul <vkoul@...nel.org>, Sasha Levin <sashal@...nel.org>,
        dmaengine@...r.kernel.org
Subject: [PATCH AUTOSEL 5.0 76/99] dmaengine: bcm2835: Avoid GFP_KERNEL in device_prep_slave_sg

From: Stefan Wahren <stefan.wahren@...e.com>

[ Upstream commit f147384774a7b24dda4783a3dcd61af272757ea8 ]

The commit af19b7ce76ba ("mmc: bcm2835: Avoid possible races on
data requests") introduces a possible circular locking dependency,
which is triggered by swapping to the sdhost interface.

So instead of reintroduce the race condition again, we could also
avoid this situation by using GFP_NOWAIT for the allocation of the
DMA buffer descriptors.

Reported-by: Aaro Koskinen <aaro.koskinen@....fi>
Signed-off-by: Stefan Wahren <stefan.wahren@...e.com>
Fixes: af19b7ce76ba ("mmc: bcm2835: Avoid possible races on data requests")
Link: http://lists.infradead.org/pipermail/linux-rpi-kernel/2019-March/008615.html
Signed-off-by: Vinod Koul <vkoul@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/dma/bcm2835-dma.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
index ae10f5614f95..bf5119203637 100644
--- a/drivers/dma/bcm2835-dma.c
+++ b/drivers/dma/bcm2835-dma.c
@@ -674,7 +674,7 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_slave_sg(
 	d = bcm2835_dma_create_cb_chain(chan, direction, false,
 					info, extra,
 					frames, src, dst, 0, 0,
-					GFP_KERNEL);
+					GFP_NOWAIT);
 	if (!d)
 		return NULL;
 
-- 
2.20.1