On 10/09/2013 10:19 AM, Lars-Peter Clausen wrote:
On 10/09/2013 09:29 AM, Qiao Zhou wrote:
Hi Mark, Liam, Jaroslav, Takashi
I met an issue in which kernel panic appears in dmaengine_pcm_dma_complete function on a quad-core system. The dmaengine_pcm_dma_complete is running core0, while snd_pcm_release has already been executed on core1, due to in low memory stress oom killer kills the audio thread to release some memory.
snd_pcm_release frees the runtime parameters, and runtime is used in dmaengine_pcm_dma_complete, which is a callback from tasklet in dmaengine. In current audio driver, we can't promise that dmaengine_pcm_dma_complete is not executed after snd_pcm_release on multi cores. Maybe we should add some protection. Do you have any suggestion?
I have tried to apply below workaround, which can fix the panic, but I'm not confident it's proper. Need your comment and better suggestion.
I think this is a general problem with your dmaengine driver, nothing audio specific. If the callback is able to run after dmaengine_terminate_all() has returned successfully there is a bug in the dmaengine driver. You need to make sure that none of the callbacks is called after terminate_all() has finished and you probably also have to make sure that the tasklet has completed, if it is running at the same time as the call to dmaengine_terminate_all().
On the other hand that last part could get tricky as the dmaengine_terminate_all() might be call from within the callback.
- Lars
From d568a88e8f66ee21d44324bdfb48d2a3106cf0d1 Mon Sep 17 00:00:00 2001 From: Qiao Zhou zhouqiao@marvell.com Date: Wed, 9 Oct 2013 15:24:29 +0800 Subject: [PATCH] ASoC: soc-dmaengine: add mutex to protect runtime param
under SMP arch, the dmaengine_pcm_dma_complete callback has the chance to run on one cpu while at the same time, the substream is released on another cpu. thus it may access param which is already freed. we need to add mutes to protect such access, and check PCM availability before using it.
Signed-off-by: Qiao Zhou zhouqiao@marvell.com
sound/soc/soc-dmaengine-pcm.c | 11 ++++++++++- 1 files changed, 10 insertions(+), 1 deletions(-)
diff --git a/sound/soc/soc-dmaengine-pcm.c b/sound/soc/soc-dmaengine-pcm.c index 111b7d9..5917029 100644 --- a/sound/soc/soc-dmaengine-pcm.c +++ b/sound/soc/soc-dmaengine-pcm.c @@ -125,13 +125,22 @@ EXPORT_SYMBOL_GPL(snd_hwparams_to_dma_slave_config); static void dmaengine_pcm_dma_complete(void *arg) { struct snd_pcm_substream *substream = arg;
- struct dmaengine_pcm_runtime_data *prtd = substream_to_prtd(substream);
struct dmaengine_pcm_runtime_data *prtd;
mutex_lock(&substream->pcm->open_mutex);
if (!substream || !substream->runtime) {
mutex_unlock(&substream->pcm->open_mutex);return;}
prtd = substream_to_prtd(substream);
prtd->pos += snd_pcm_lib_period_bytes(substream); if (prtd->pos >= snd_pcm_lib_buffer_bytes(substream)) prtd->pos = 0;
snd_pcm_period_elapsed(substream);
mutex_unlock(&substream->pcm->open_mutex);
}
static int dmaengine_pcm_prepare_and_submit(struct snd_pcm_substream *substream)
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