[PATCH 1/1] dmaengine: dw: resolve recursion lock when audio playback

["yitian" <yitian.bu@tangramtek.com>]

when audio playback is running, user space will call
snd_pcm_lib_write1() function, it will first get pcm stream lock,
after that it may call function snd_pcm_update_hw_ptr(), the call
stack will be as below:
  snd_pcm_lib_write1  <-- got pcm stream lock
   --> snd_pcm_update_hw_ptr
     --> dwc_tx_status
      --> dwc_scan_descriptors
       --> callback
        --> dmaengine_pcm_dma_complete
         --> snd_pcm_period_elapsed <-- get stream lock again
recursion lock occurs in snd_pcm_period_elapsed function.
remove dwc_scan_descriptors from dwc_tx_status can fix this issue.

Signed-off-by: Yitian Bu <yitian.bu@tangramtek.com>
---
 drivers/dma/dw/core.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c
index cf1c87f..5341b44 100644
--- a/drivers/dma/dw/core.c
+++ b/drivers/dma/dw/core.c
@@ -1078,11 +1078,7 @@ dwc_tx_status(struct dma_chan *chan,
 	ret = dma_cookie_status(chan, cookie, txstate);
 	if (ret == DMA_COMPLETE)
 		return ret;
-
-	dwc_scan_descriptors(to_dw_dma(chan->device), dwc);
-
-	ret = dma_cookie_status(chan, cookie, txstate);
-	if (ret != DMA_COMPLETE)
+	else
 		dma_set_residue(txstate, dwc_get_residue(dwc));
 
 	if (dwc->paused && ret == DMA_IN_PROGRESS)
-- 
1.7.12.4



Yitian
Best Regards