Hi, Koba Ko
Thanks for your patch.
I've had the same problem,see
https://lore.kernel.org/all/20220716024453.1418259-1-haijie1@xxxxxxxxxx/.
The two operations of updating client_count, that is,
chan->client_count++;
balance_ref_count(chan);
the order of which is modified by d2f4f99db3e9 ("dmaengine: Rework
dma_chan_get").
I have complied and tested it on my arm64 and this patch does
fix the problem.
For this patch,
Reviewed-by: Jie Hai <haijie1@xxxxxxxxxx>
Test-by: Jie Hai <haijie1@xxxxxxxxxx>
Best regards,
Jie Hai
On 2022/8/30 17:32, Koba Ko wrote:
If the passed client_count is 0,
it would be incremented by balance_ref_count first
then increment one more.
This would cause client_count to 2.
cat /sys/class/dma/dma0chan*/in_use
2
2
2
Fixes: d2f4f99db3e9 ("dmaengine: Rework dma_chan_get")
Signed-off-by: Koba Ko <koba.ko@xxxxxxxxxxxxx>
---
drivers/dma/dmaengine.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 2cfa8458b51be..78f8a9f3ad825 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -451,7 +451,8 @@ static int dma_chan_get(struct dma_chan *chan)
/* The channel is already in use, update client count */
if (chan->client_count) {
__module_get(owner);
- goto out;
+ chan->client_count++;
+ return 0;
}
if (!try_module_get(owner))
@@ -470,11 +471,11 @@ static int dma_chan_get(struct dma_chan *chan)
goto err_out;
}
+ chan->client_count++;
+
if (!dma_has_cap(DMA_PRIVATE, chan->device->cap_mask))
balance_ref_count(chan);
-out:
- chan->client_count++;
return 0;
err_out:
