On Tue, Oct 20, 2015 at 12:46 PM, Lars-Peter Clausen <lars@xxxxxxxxxx> 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.
> +
> + ret = dmaengine_terminate_async(chan);
> + if (ret)
> + return ret;
> +
> + dmaengine_synchronize(chan);
> +
> + return 0;
> +}
--
With Best Regards,
Andy Shevchenko
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