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async_tx: remove walk of tx->parent chain in dma_wait_for_async_tx
We currently walk the parent chain when waiting for a given tx to complete however this walk may race with the driver cleanup routine. The routines in async_raid6_recov.c may fall back to the synchronous path at any point so we need to be prepared to call async_tx_quiesce() (which calls dma_wait_for_async_tx). To remove the ->parent walk we guarantee that every time a dependency is attached ->issue_pending() is invoked, then we can simply poll the initial descriptor until completion. This also allows for a lighter weight 'issue pending' implementation as there is no longer a requirement to iterate through all the channels' ->issue_pending() routines as long as operations have been submitted in an ordered chain. async_tx_issue_pending() is added for this case. Signed-off-by: Dan Williams <dan.j.williams@intel.com>
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af1f951eb6
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3 changed files with 40 additions and 41 deletions
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@ -83,6 +83,24 @@ struct async_submit_ctl {
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#ifdef CONFIG_DMA_ENGINE
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#define async_tx_issue_pending_all dma_issue_pending_all
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/**
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* async_tx_issue_pending - send pending descriptor to the hardware channel
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* @tx: descriptor handle to retrieve hardware context
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*
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* Note: any dependent operations will have already been issued by
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* async_tx_channel_switch, or (in the case of no channel switch) will
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* be already pending on this channel.
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*/
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static inline void async_tx_issue_pending(struct dma_async_tx_descriptor *tx)
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{
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if (likely(tx)) {
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struct dma_chan *chan = tx->chan;
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struct dma_device *dma = chan->device;
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dma->device_issue_pending(chan);
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}
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}
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#ifdef CONFIG_ARCH_HAS_ASYNC_TX_FIND_CHANNEL
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#include <asm/async_tx.h>
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#else
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@ -98,6 +116,11 @@ static inline void async_tx_issue_pending_all(void)
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do { } while (0);
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}
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static inline void async_tx_issue_pending(struct dma_async_tx_descriptor *tx)
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{
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do { } while (0);
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}
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static inline struct dma_chan *
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async_tx_find_channel(struct async_submit_ctl *submit,
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enum dma_transaction_type tx_type, struct page **dst,
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