[PATCH v3 07/12] dmaengine: at_xdmac: Fix concurrency over xfers_list

Tudor Ambarus
2021-12-15T11:01:42Z

Since tx_submit can be called from a hard IRQ, xfers_list must be
protected with a lock to avoid concurency on the list's elements.
Since at_xdmac_handle_cyclic() is called from a tasklet, spin_lock_irq
is enough to protect from a hard IRQ.

Fixes: e1f7c9eee707 ("dmaengine: at_xdmac: creation of the atmel eXtended DMA Controller driver")
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
---
drivers/dma/at_xdmac.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
index b6547f1b5645..eeb03065d484 100644
--- a/drivers/dma/at_xdmac.c
+++ b/drivers/dma/at_xdmac.c
@@ -1608,14 +1608,17 @@ static void at_xdmac_handle_cyclic(struct at_xdmac_chan *atchan)
struct at_xdmac_desc *desc;
struct dma_async_tx_descriptor *txd;

- if (!list_empty(&atchan->xfers_list)) {
- desc = list_first_entry(&atchan->xfers_list,
- struct at_xdmac_desc, xfer_node);
- txd = &desc->tx_dma_desc;
-
- if (txd->flags & DMA_PREP_INTERRUPT)
- dmaengine_desc_get_callback_invoke(txd, NULL);
+ spin_lock_irq(&atchan->lock);
+ if (list_empty(&atchan->xfers_list)) {
+ spin_unlock_irq(&atchan->lock);
+ return;
}
+ desc = list_first_entry(&atchan->xfers_list, struct at_xdmac_desc,
+ xfer_node);
+ spin_unlock_irq(&atchan->lock);
+ txd = &desc->tx_dma_desc;
+ if (txd->flags & DMA_PREP_INTERRUPT)
+ dmaengine_desc_get_callback_invoke(txd, NULL);
}

static void at_xdmac_handle_error(struct at_xdmac_chan *atchan)
--
2.25.1