* [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; 3+ 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: bcm-kernel-feedback-list, Aaro Koskinen, Lukas Wunner,
Florian Kauer, Martin Sperl, dmaengine, linux-arm-kernel,
linux-rpi-kernel, Stefan Wahren
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;
^ permalink raw reply related [flat|nested] 3+ messages in thread
* [RFC] dmaengine: bcm2835: Avoid GFP_KERNEL in device_prep_slave_sg
@ 2019-04-23 5:11 ` Vinod Koul
2019-04-23 5:11 ` [PATCH RFC] " Vinod Koul
0 siblings, 1 reply; 3+ messages in thread
From: Vinod Koul @ 2019-04-23 5:11 UTC (permalink / raw)
To: Stefan Wahren
Cc: Dan Williams, Florian Fainelli, Ray Jui, Scott Branden,
Eric Anholt, bcm-kernel-feedback-list, Aaro Koskinen,
Lukas Wunner, Florian Kauer, Martin Sperl, dmaengine,
linux-arm-kernel, 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
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH RFC] dmaengine: bcm2835: Avoid GFP_KERNEL in device_prep_slave_sg
2019-04-23 5:11 ` Vinod Koul
@ 2019-04-23 5:11 ` Vinod Koul
0 siblings, 0 replies; 3+ messages in thread
From: Vinod Koul @ 2019-04-23 5:11 UTC (permalink / raw)
To: Stefan Wahren
Cc: Dan Williams, Florian Fainelli, Ray Jui, Scott Branden,
Eric Anholt, bcm-kernel-feedback-list, Aaro Koskinen,
Lukas Wunner, Florian Kauer, Martin Sperl, dmaengine,
linux-arm-kernel, 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
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-04-01 18:38 [RFC] dmaengine: bcm2835: Avoid GFP_KERNEL in device_prep_slave_sg Stefan Wahren
2019-04-23 5:11 ` Vinod Koul
2019-04-23 5:11 ` [PATCH RFC] " Vinod Koul
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