[PATCH] dmaengine: virt-dma : fix vchan error on multi-thread

[Jie Hai <haijie1@huawei.com>]

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@huawei.com>
---
 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 ++++++++++++++++++--
 4 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/drivers/dma/fsl-edma-common.c b/drivers/dma/fsl-edma-common.c
index a06a1575a2a5..c6d2e54ab85d 100644
--- a/drivers/dma/fsl-edma-common.c
+++ b/drivers/dma/fsl-edma-common.c
@@ -674,7 +674,7 @@ 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 eddb2688f234..5ffd7ba92058 100644
--- a/drivers/dma/fsl-qdma.c
+++ b/drivers/dma/fsl-qdma.c
@@ -311,7 +311,7 @@ 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 d1c6956af452..f35dc68e1a7c 100644
--- a/drivers/dma/sf-pdma/sf-pdma.c
+++ b/drivers/dma/sf-pdma/sf-pdma.c
@@ -144,7 +144,7 @@ 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 e9f5250fbe4d..65b4f3bdecf7 100644
--- a/drivers/dma/virt-dma.h
+++ b/drivers/dma/virt-dma.h
@@ -177,13 +177,29 @@ static inline struct virt_dma_desc *vchan_next_desc(struct virt_dma_chan *vc)
 static inline void vchan_get_all_descriptors(struct virt_dma_chan *vc,
 	struct list_head *head)
 {
-	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;
@@ -191,7 +207,7 @@ 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