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SubjectRe: [PATCH 1/1] dmaengine: dw: resolve recursion lock when audio playback
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On 26 September 2015 at 05:38, yitian <yitian.bu@tangramtek.com> wrote:
> 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(-)

I am not sure if this is a sane way of doing that, and we were scanning
the descriptors for some valid reason..

Though, I am on vacation for few days now and will be able to look
at the details later.


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