[PATCH v2] dmaegine: virt-dma : Fix multi-user with vchan

[Jie Hai]

List desc_allocated was introduced for the case of a transfer
submitted multiple times. But elegating descriptors on the list
causes other problems.

For example, in the multi-thread scenario, which tasks are
continuously created and submitted by each thread. If one of
the threads calls dmaengine_terminate_all, for dirvers using
vchan_get_all_descriptors, all descriptors will be freed. If
there's another thread submitting a transfer A by
vchan_tx_submit, the following results may be generated:
1. desc A is freeing -> visit wrong address of node prep/next.
2. desc A is freed -> visit invalid address of A.

In the above case, calltrace is generated and the system is
suspended. This can be tested by dmatest.

This patch removes desc_allocated from vchan_get_all_descriptors,
and add new function 'vchan_get_all_allocated_descs' to get all
descriptors ever allocated.

And apply vchan_get_all_allocated_descs to free chan resource and
vchan_get_all_descriptors to terminate all transfers, respectively.
This avoids freeing up descriptors in use by other threads.

Signed-off-by: Jie Hai <haijie1 at huawei.com>
---
 drivers/dma/fsl-dpaa2-qdma/dpaa2-qdma.c |  2 +-
 drivers/dma/fsl-edma-common.c           |  2 +-
 drivers/dma/fsl-qdma.c                  |  2 +-
 drivers/dma/sf-pdma/sf-pdma.c           |  2 +-
 drivers/dma/virt-dma.h                  | 20 ++++++++++++++++++--
 5 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/drivers/dma/fsl-dpaa2-qdma/dpaa2-qdma.c b/drivers/dma/fsl-dpaa2-qdma/dpaa2-qdma.c
index 36384d019263..efdecf15e1b3 100644
--- a/drivers/dma/fsl-dpaa2-qdma/dpaa2-qdma.c
+++ b/drivers/dma/fsl-dpaa2-qdma/dpaa2-qdma.c
@@ -71,7 +71,7 @@ static void dpaa2_qdma_free_chan_resources(struct dma_chan *chan)
 	LIST_HEAD(head);
 
 	spin_lock_irqsave(&dpaa2_chan->vchan.lock, flags);
-	vchan_get_all_descriptors(&dpaa2_chan->vchan, &head);
+	vchan_get_all_allocated_descs(&dpaa2_chan->vchan, &head);
 	spin_unlock_irqrestore(&dpaa2_chan->vchan.lock, flags);
 
 	vchan_dma_desc_free_list(&dpaa2_chan->vchan, &head);
diff --git a/drivers/dma/fsl-edma-common.c b/drivers/dma/fsl-edma-common.c
index 3af430787315..1e0ad87eb7fa 100644
--- a/drivers/dma/fsl-edma-common.c
+++ b/drivers/dma/fsl-edma-common.c
@@ -828,7 +828,7 @@ void fsl_edma_free_chan_resources(struct dma_chan *chan)
 	if (edma->drvdata->dmamuxs)
 		fsl_edma_chan_mux(fsl_chan, 0, false);
 	fsl_chan->edesc = NULL;
-	vchan_get_all_descriptors(&fsl_chan->vchan, &head);
+	vchan_get_all_allocated_descs(&fsl_chan->vchan, &head);
 	fsl_edma_unprep_slave_dma(fsl_chan);
 	spin_unlock_irqrestore(&fsl_chan->vchan.lock, flags);
 
diff --git a/drivers/dma/fsl-qdma.c b/drivers/dma/fsl-qdma.c
index 5005e138fc23..7af428db404e 100644
--- a/drivers/dma/fsl-qdma.c
+++ b/drivers/dma/fsl-qdma.c
@@ -316,7 +316,7 @@ static void fsl_qdma_free_chan_resources(struct dma_chan *chan)
 	LIST_HEAD(head);
 
 	spin_lock_irqsave(&fsl_chan->vchan.lock, flags);
-	vchan_get_all_descriptors(&fsl_chan->vchan, &head);
+	vchan_get_all_allocated_descs(&fsl_chan->vchan, &head);
 	spin_unlock_irqrestore(&fsl_chan->vchan.lock, flags);
 
 	vchan_dma_desc_free_list(&fsl_chan->vchan, &head);
diff --git a/drivers/dma/sf-pdma/sf-pdma.c b/drivers/dma/sf-pdma/sf-pdma.c
index 428473611115..4dc8a8c8ad80 100644
--- a/drivers/dma/sf-pdma/sf-pdma.c
+++ b/drivers/dma/sf-pdma/sf-pdma.c
@@ -147,7 +147,7 @@ static void sf_pdma_free_chan_resources(struct dma_chan *dchan)
 	sf_pdma_disable_request(chan);
 	kfree(chan->desc);
 	chan->desc = NULL;
-	vchan_get_all_descriptors(&chan->vchan, &head);
+	vchan_get_all_allocated_descs(&chan->vchan, &head);
 	sf_pdma_disclaim_chan(chan);
 	spin_unlock_irqrestore(&chan->vchan.lock, flags);
 	vchan_dma_desc_free_list(&chan->vchan, &head);
diff --git a/drivers/dma/virt-dma.h b/drivers/dma/virt-dma.h
index 59d9eabc8b67..4492641b79f6 100644
--- a/drivers/dma/virt-dma.h
+++ b/drivers/dma/virt-dma.h
@@ -187,13 +187,29 @@ static inline void vchan_get_all_descriptors(struct virt_dma_chan *vc,
 {
 	lockdep_assert_held(&vc->lock);
 
-	list_splice_tail_init(&vc->desc_allocated, head);
 	list_splice_tail_init(&vc->desc_submitted, head);
 	list_splice_tail_init(&vc->desc_issued, head);
 	list_splice_tail_init(&vc->desc_completed, head);
 	list_splice_tail_init(&vc->desc_terminated, head);
 }
 
+/**
+ * vchan_get_all_allocated_descs - obtain all descriptors
+ * @vc: virtual channel to get descriptors from
+ * @head: list of descriptors found
+ *
+ * vc.lock must be held by caller
+ *
+ * Removes all descriptors from internal lists, and provides a list of all
+ * descriptors found
+ */
+static inline void vchan_get_all_allocated_descs(struct virt_dma_chan *vc,
+	struct list_head *head)
+{
+	list_splice_tail_init(&vc->desc_allocated, head);
+	vchan_get_all_descriptors(vc, head);
+}
+
 static inline void vchan_free_chan_resources(struct virt_dma_chan *vc)
 {
 	struct virt_dma_desc *vd;
@@ -201,7 +217,7 @@ static inline void vchan_free_chan_resources(struct virt_dma_chan *vc)
 	LIST_HEAD(head);
 
 	spin_lock_irqsave(&vc->lock, flags);
-	vchan_get_all_descriptors(vc, &head);
+	vchan_get_all_allocated_descs(vc, &head);
 	list_for_each_entry(vd, &head, node)
 		dmaengine_desc_clear_reuse(&vd->tx);
 	spin_unlock_irqrestore(&vc->lock, flags);
-- 
2.33.0