From: Ludovic Desroches <ludovic.desroc...@atmel.com>
The BUG_ON() directive is triggered probably due to a latency modification
following inclusion of c10d736 (softirq: reduce latencies).
This condition has not been met before 3.9-rc1 and doesn't trigger without
this patch.
We now make sure that DMA channel is idle before calling atc_complete_all()
which makes the BUG_ON() "protection" useless.
Signed-off-by: Ludovic Desroches <ludovic.desroc...@atmel.com>
Signed-off-by: Nicolas Ferre <nicolas.fe...@atmel.com>
---
Linus,
We have identified a race condition on the Atmel ARM-based AT91 DMA controller
driver that leads to hitting a BUG_ON() directive.
This error, only triggered after the inclusion of a patch that reduces the
softirq latency, is affecting several AT91 SoCs and can be seen
as a regression by people using the dmaengine driver (on NAND flash
accesses for instance).
I know that it is late in the development cycle but can you please consider
including it in your tree before 3.9-final?
This patch can also go through dmaengine tree (Vinod Koul) but I do not know if
there is enough time remaining.
Thanks a lot, best regards,
Nicolas Ferre
drivers/dma/at_hdmac.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
index 6e13f26..88cfc61 100644
--- a/drivers/dma/at_hdmac.c
+++ b/drivers/dma/at_hdmac.c
@@ -310,8 +310,6 @@ static void atc_complete_all(struct at_dma_chan *atchan)
dev_vdbg(chan2dev(&atchan->chan_common), "complete all\n");
- BUG_ON(atc_chan_is_enabled(atchan));
-
/*
* Submit queued descriptors ASAP, i.e. before we go through
* the completed ones.
@@ -368,6 +366,9 @@ static void atc_advance_work(struct at_dma_chan *atchan)
{
dev_vdbg(chan2dev(&atchan->chan_common), "advance_work\n");
+ if (atc_chan_is_enabled(atchan))
+ return;
+
if (list_empty(&atchan->active_list) ||
list_is_singular(&atchan->active_list)) {
atc_complete_all(atchan);
@@ -1078,9 +1079,7 @@ static void atc_issue_pending(struct dma_chan *chan)
return;
spin_lock_irqsave(&atchan->lock, flags);
- if (!atc_chan_is_enabled(atchan)) {
- atc_advance_work(atchan);
- }
+ atc_advance_work(atchan);
spin_unlock_irqrestore(&atchan->lock, flags);
}
--
1.8.0
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