* [PATCH RFC] dmaengine: bcm2835: Avoid GFP_KERNEL in device_prep_slave_sg
@ 2019-04-01 18:38 Stefan Wahren
2019-04-23 5:11 ` Vinod Koul
0 siblings, 1 reply; 2+ messages in thread
From: Stefan Wahren @ 2019-04-01 18:38 UTC (permalink / raw)
To: Dan Williams, Vinod Koul, Florian Fainelli, Ray Jui,
Scott Branden, Eric Anholt
Cc: Stefan Wahren, Aaro Koskinen, Lukas Wunner,
bcm-kernel-feedback-list, linux-arm-kernel, dmaengine,
Martin Sperl, Florian Kauer, linux-rpi-kernel
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@iki.fi>
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Fixes: af19b7ce76ba ("mmc: bcm2835: Avoid possible races on data requests")
Link: http://lists.infradead.org/pipermail/linux-rpi-kernel/2019-March/008615.html
---
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 ec8a291..54093ff 100644
--- a/drivers/dma/bcm2835-dma.c
+++ b/drivers/dma/bcm2835-dma.c
@@ -671,7 +671,7 @@ 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;
--
2.7.4
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^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH RFC] dmaengine: bcm2835: Avoid GFP_KERNEL in device_prep_slave_sg
2019-04-01 18:38 [PATCH RFC] dmaengine: bcm2835: Avoid GFP_KERNEL in device_prep_slave_sg Stefan Wahren
@ 2019-04-23 5:11 ` Vinod Koul
0 siblings, 0 replies; 2+ messages in thread
From: Vinod Koul @ 2019-04-23 5:11 UTC (permalink / raw)
To: Stefan Wahren
Cc: Florian Fainelli, Scott Branden, Aaro Koskinen, Ray Jui,
Eric Anholt, Lukas Wunner, bcm-kernel-feedback-list,
linux-arm-kernel, dmaengine, Martin Sperl, Dan Williams,
Florian Kauer, linux-rpi-kernel
On 01-04-19, 20:38, Stefan Wahren wrote:
> 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.
Applied, thanks
--
~Vinod
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linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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2019-04-01 18:38 [PATCH RFC] dmaengine: bcm2835: Avoid GFP_KERNEL in device_prep_slave_sg Stefan Wahren
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