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Re: [PATCH 1/4] dmaengine: Add transfer termination synchronization support

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On 10/29/2015 10:59 PM, Andy Shevchenko wrote:
> On Tue, Oct 20, 2015 at 12:46 PM, Lars-Peter Clausen <lars@metafoo.de> wrote:
>> The DMAengine API has a long standing race condition that is inherent to
>> the API itself. Calling dmaengine_terminate_all() is supposed to stop and
>> abort any pending or active transfers that have previously been submitted.
>> Unfortunately it is possible that this operation races against a currently
>> running (or with some drivers also scheduled) completion callback.
> 
> []
> 
>> +/**
>> + * dmaengine_terminate_sync() - Terminate all active DMA transfers
>> + * @chan: The channel for which to terminate the transfers
>> + *
>> + * Calling this function will terminate all active and pending transfers
>> + * that have previously been submitted to the channel. It is similar to
>> + * dmaengine_terminate_async() but guarantees that the DMA transfer has actually
>> + * stopped and that all complete callbacks have finished running when the
>> + * function returns.
>> + *
>> + * This function must only be called from non-atomic context and must not be
>> + * called from within a complete callback of a descriptor submitted on the same
>> + * channel.
>> + */
>> +static inline int dmaengine_terminate_sync(struct dma_chan *chan)
>> +{
>> +       int ret;
> 
> Might be a good idea to add might_sleep(); here.

Sound like a good idea, thanks, I'll add it (in dmaengine_synchronize() though).

> 
>> +
>> +       ret = dmaengine_terminate_async(chan);
>> +       if (ret)
>> +               return ret;
>> +
>> +       dmaengine_synchronize(chan);
>> +
>> +       return 0;
>> +}
> 
> 

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[PATCH 0/4] dmaengine: Add transfer termination synchronization support Lars-Peter Clausen <lars@metafoo.de> - 2015-10-20 11:50 +0200
  [PATCH 4/4] ALSA: pcm_dmaengine: Properly synchronize DMA on shutdown Lars-Peter Clausen <lars@metafoo.de> - 2015-10-20 11:50 +0200
    Re: [PATCH 4/4] ALSA: pcm_dmaengine: Properly synchronize DMA on shutdown Takashi Iwai <tiwai@suse.de> - 2015-10-20 13:20 +0200
      Re: [PATCH 4/4] ALSA: pcm_dmaengine: Properly synchronize DMA on  shutdown Lars-Peter Clausen <lars@metafoo.de> - 2015-10-20 13:50 +0200
        Re: [PATCH 4/4] ALSA: pcm_dmaengine: Properly synchronize DMA on shutdown Takashi Iwai <tiwai@suse.de> - 2015-10-20 14:40 +0200
        Re: [PATCH 4/4] ALSA: pcm_dmaengine: Properly synchronize DMA on  shutdown Lars-Peter Clausen <lars@metafoo.de> - 2015-10-20 15:10 +0200
  [PATCH 2/4] dmaengine: virt-dma: Add synchronization helper function Lars-Peter Clausen <lars@metafoo.de> - 2015-10-20 11:50 +0200
  [PATCH 1/4] dmaengine: Add transfer termination synchronization support Lars-Peter Clausen <lars@metafoo.de> - 2015-10-20 11:50 +0200
    Re: [PATCH 1/4] dmaengine: Add transfer termination synchronization support Andy Shevchenko <andy.shevchenko@gmail.com> - 2015-10-29 23:10 +0100
      Re: [PATCH 1/4] dmaengine: Add transfer termination synchronization  support Lars-Peter Clausen <lars@metafoo.de> - 2015-10-30 15:20 +0100
  [PATCH 3/4] dmaengine: axi_dmac: Add synchronization support Lars-Peter Clausen <lars@metafoo.de> - 2015-10-20 11:50 +0200
  Re: [PATCH 0/4] dmaengine: Add transfer termination synchronization  support Vinod Koul <vinod.koul@intel.com> - 2015-10-29 02:30 +0100

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