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From: Tudor Ambarus <tudor.ambarus@microchip.com>
To: <ludovic.desroches@microchip.com>, <vkoul@kernel.org>,
	<richard.genoud@gmail.com>, <gregkh@linuxfoundation.org>,
	<jirislaby@kernel.org>
Cc: <nicolas.ferre@microchip.com>, <alexandre.belloni@bootlin.com>,
	<mripard@kernel.org>, <linux-arm-kernel@lists.infradead.org>,
	<dmaengine@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<linux-serial@vger.kernel.org>,
	Tudor Ambarus <tudor.ambarus@microchip.com>
Subject: [PATCH v2 07/13] dmaengine: at_xdmac: Fix race for the tx desc callback
Date: Thu, 25 Nov 2021 11:00:22 +0200	[thread overview]
Message-ID: <20211125090028.786832-8-tudor.ambarus@microchip.com> (raw)
In-Reply-To: <20211125090028.786832-1-tudor.ambarus@microchip.com>

The transfer descriptors were wrongly moved to the free descriptors list
before calling the tx desc callback. As the DMA engine drivers drop any
locks before calling the callback function, txd could be taken again,
resulting in its callback called prematurely.

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 | 25 ++++++++-----------------
 1 file changed, 8 insertions(+), 17 deletions(-)

diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
index 4d8476845c20..2cc9af222681 100644
--- a/drivers/dma/at_xdmac.c
+++ b/drivers/dma/at_xdmac.c
@@ -1582,20 +1582,6 @@ at_xdmac_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
 	return ret;
 }
 
-/* Call must be protected by lock. */
-static void at_xdmac_remove_xfer(struct at_xdmac_chan *atchan,
-				    struct at_xdmac_desc *desc)
-{
-	dev_dbg(chan2dev(&atchan->chan), "%s: desc 0x%p\n", __func__, desc);
-
-	/*
-	 * Remove the transfer from the transfer list then move the transfer
-	 * descriptors into the free descriptors list.
-	 */
-	list_del(&desc->xfer_node);
-	list_splice_init(&desc->descs_list, &atchan->free_descs_list);
-}
-
 static void at_xdmac_advance_work(struct at_xdmac_chan *atchan)
 {
 	struct at_xdmac_desc	*desc;
@@ -1704,7 +1690,8 @@ static void at_xdmac_tasklet(struct tasklet_struct *t)
 
 		txd = &desc->tx_dma_desc;
 		dma_cookie_complete(txd);
-		at_xdmac_remove_xfer(atchan, desc);
+		/* Remove the transfer from the transfer list. */
+		list_del(&desc->xfer_node);
 		spin_unlock_irq(&atchan->lock);
 
 		if (txd->flags & DMA_PREP_INTERRUPT)
@@ -1713,6 +1700,8 @@ static void at_xdmac_tasklet(struct tasklet_struct *t)
 		dma_run_dependencies(txd);
 
 		spin_lock_irq(&atchan->lock);
+		/* Move the xfer descriptors into the free descriptors list. */
+		list_splice_init(&desc->descs_list, &atchan->free_descs_list);
 		at_xdmac_advance_work(atchan);
 		spin_unlock_irq(&atchan->lock);
 	}
@@ -1859,8 +1848,10 @@ static int at_xdmac_device_terminate_all(struct dma_chan *chan)
 		cpu_relax();
 
 	/* Cancel all pending transfers. */
-	list_for_each_entry_safe(desc, _desc, &atchan->xfers_list, xfer_node)
-		at_xdmac_remove_xfer(atchan, desc);
+	list_for_each_entry_safe(desc, _desc, &atchan->xfers_list, xfer_node) {
+		list_del(&desc->xfer_node);
+		list_splice_init(&desc->descs_list, &atchan->free_descs_list);
+	}
 
 	clear_bit(AT_XDMAC_CHAN_IS_PAUSED, &atchan->status);
 	clear_bit(AT_XDMAC_CHAN_IS_CYCLIC, &atchan->status);
-- 
2.25.1


  parent reply	other threads:[~2021-11-25  9:03 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-25  9:00 [PATCH v2 00/13] dmaengine: at_xdmac: Various fixes Tudor Ambarus
2021-11-25  9:00 ` [PATCH v2 01/13] dmaengine: at_xdmac: Don't start transactions at tx_submit level Tudor Ambarus
2021-11-25  9:00 ` [PATCH v2 02/13] tty: serial: atmel: Check return code of dmaengine_submit() Tudor Ambarus
2021-11-25  9:00 ` [PATCH v2 03/13] tty: serial: atmel: Call dma_async_issue_pending() Tudor Ambarus
2021-11-25  9:00 ` [PATCH v2 04/13] dmaengine: at_xdmac: Start transfer for cyclic channels in issue_pending Tudor Ambarus
2021-11-25  9:00 ` [PATCH v2 05/13] dmaengine: at_xdmac: Print debug message after realeasing the lock Tudor Ambarus
2021-11-25  9:00 ` [PATCH v2 06/13] dmaengine: at_xdmac: Fix concurrency over chan's completed_cookie Tudor Ambarus
2021-11-25  9:00 ` Tudor Ambarus [this message]
2021-11-25  9:00 ` [PATCH v2 08/13] dmaengine: at_xdmac: Move the free desc to the tail of the desc list Tudor Ambarus
2021-12-13  8:07   ` Vinod Koul
2021-12-13  8:51     ` Tudor.Ambarus
2021-12-13  8:59       ` Vinod Koul
2021-12-13  9:00         ` Vinod Koul
2021-12-13  9:22           ` Tudor.Ambarus
2021-12-13  9:27             ` Tudor.Ambarus
2021-11-25  9:00 ` [PATCH v2 09/13] dmaengine: at_xdmac: Fix concurrency over xfers_list Tudor Ambarus
2021-11-25  9:00 ` [PATCH v2 10/13] dmaengine: at_xdmac: Remove a level of indentation in at_xdmac_advance_work() Tudor Ambarus
2021-11-25  9:00 ` [PATCH v2 11/13] dmaengine: at_xdmac: Fix lld view setting Tudor Ambarus
2021-11-25  9:00 ` [PATCH v2 12/13] dmaengine: at_xdmac: Fix at_xdmac_lld struct definition Tudor Ambarus
2021-11-25  9:00 ` [PATCH v2 13/13] dmaengine: at_xdmac: Fix race over irq_status Tudor Ambarus

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