From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lars-Peter Clausen Subject: Re: async between dmaengine_pcm_dma_complete and snd_pcm_release Date: Wed, 09 Oct 2013 10:30:14 +0200 Message-ID: <52551416.9020004@metafoo.de> References: <525505C2.4070201@marvell.com> <5255119D.9020303@metafoo.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from smtp-out-202.synserver.de (smtp-out-202.synserver.de [212.40.185.202]) by alsa0.perex.cz (Postfix) with ESMTP id A3F112607BB for ; Wed, 9 Oct 2013 10:28:16 +0200 (CEST) In-Reply-To: <5255119D.9020303@metafoo.de> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: Qiao Zhou Cc: "alsa-devel@alsa-project.org" , "tiwai@suse.de" , lgirdwood@gmail.com, Mark Brown , "zhangfei.gao@gmail.com" , trinity.qiao.zhou@gmail.com, Chao Xie List-Id: alsa-devel@alsa-project.org 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 >> 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 >> --- >> 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) > > _______________________________________________ > Alsa-devel mailing list > Alsa-devel@alsa-project.org > http://mailman.alsa-project.org/mailman/listinfo/alsa-devel >