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FAILED: patch "[PATCH] dmaengine: at_xdmac: Fix concurrency over xfers_list" failed to apply to 4.9-stable tree

PATCH [email protected] 1 participant 1 message Jan 24, 2022

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The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 18deddea9184b62941395889ff7659529c877326 Mon Sep 17 00:00:00 2001
From: Tudor Ambarus <[email protected]>
Date: Wed, 15 Dec 2021 13:01:10 +0200
Subject: [PATCH] dmaengine: at_xdmac: Fix concurrency over xfers_list

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 <[email protected]>
Link https://lore.kernel.org/r/[email protected] open here
Signed-off-by Vinod Koul <[email protected]>
drivers/dma/at_xdmac.c +10 -7
index b6547f1b5645..eeb03065d484 100644
@@ -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)