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async_tx: remove walk of tx->parent chain in dma_wait_for_async_tx

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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 <[email protected]>
This commit is contained in:
Dan Williams 2009-07-14 12:19:02 -07:00
commit 95475e5711
3 changed files with 40 additions and 41 deletions
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13
crypto/async_tx/async_tx.c
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@ -77,8 +77,8 @@ static void
async_tx_channel_switch(struct dma_async_tx_descriptor *depend_tx,
struct dma_async_tx_descriptor *tx)
{
struct dma_chan *chan;
struct dma_device *device;
struct dma_chan *chan = depend_tx->chan;
struct dma_device *device = chan->device;
struct dma_async_tx_descriptor *intr_tx = (void *) ~0;
/* first check to see if we can still append to depend_tx */
@ -90,11 +90,11 @@ async_tx_channel_switch(struct dma_async_tx_descriptor *depend_tx,
}
spin_unlock_bh(&depend_tx->lock);
if (!intr_tx)
/* attached dependency, flush the parent channel */
if (!intr_tx) {
device->device_issue_pending(chan);
return;
chan = depend_tx->chan;
device = chan->device;
}
/* see if we can schedule an interrupt
* otherwise poll for completion
@ -128,6 +128,7 @@ async_tx_channel_switch(struct dma_async_tx_descriptor *depend_tx,
intr_tx->tx_submit(intr_tx);
async_tx_ack(intr_tx);
}
device->device_issue_pending(chan);
} else {
if (dma_wait_for_async_tx(depend_tx) == DMA_ERROR)
panic("%s: DMA_ERROR waiting for depend_tx\n",