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authorDan Williams <dan.j.williams@intel.com>2009-07-14 12:19:02 -0700
committerDan Williams <dan.j.williams@intel.com>2009-08-29 19:09:27 -0700
commit95475e57113c66aac7583925736ed2e2d58c990d (patch)
tree933aa0ca3bffef5b1457c516fbe3e8690b4c4cb1 /drivers/dma
parentaf1f951eb6ef27b01cbfb3f6c21b770af4368a6d (diff)
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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>
Diffstat (limited to 'drivers/dma')
-rw-r--r--drivers/dma/dmaengine.c45
1 files changed, 10 insertions, 35 deletions
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 6781e8f..e002e0e 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -934,49 +934,24 @@ EXPORT_SYMBOL(dma_async_tx_descriptor_init);
/* dma_wait_for_async_tx - spin wait for a transaction to complete
* @tx: in-flight transaction to wait on
- *
- * This routine assumes that tx was obtained from a call to async_memcpy,
- * async_xor, async_memset, etc which ensures that tx is "in-flight" (prepped
- * and submitted). Walking the parent chain is only meant to cover for DMA
- * drivers that do not implement the DMA_INTERRUPT capability and may race with
- * the driver's descriptor cleanup routine.
*/
enum dma_status
dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx)
{
- enum dma_status status;
- struct dma_async_tx_descriptor *iter;
- struct dma_async_tx_descriptor *parent;
+ unsigned long dma_sync_wait_timeout = jiffies + msecs_to_jiffies(5000);
if (!tx)
return DMA_SUCCESS;
- WARN_ONCE(tx->parent, "%s: speculatively walking dependency chain for"
- " %s\n", __func__, dma_chan_name(tx->chan));
-
- /* poll through the dependency chain, return when tx is complete */
- do {
- iter = tx;
-
- /* find the root of the unsubmitted dependency chain */
- do {
- parent = iter->parent;
- if (!parent)
- break;
- else
- iter = parent;
- } while (parent);
-
- /* there is a small window for ->parent == NULL and
- * ->cookie == -EBUSY
- */
- while (iter->cookie == -EBUSY)
- cpu_relax();
-
- status = dma_sync_wait(iter->chan, iter->cookie);
- } while (status == DMA_IN_PROGRESS || (iter != tx));
-
- return status;
+ while (tx->cookie == -EBUSY) {
+ if (time_after_eq(jiffies, dma_sync_wait_timeout)) {
+ pr_err("%s timeout waiting for descriptor submission\n",
+ __func__);
+ return DMA_ERROR;
+ }
+ cpu_relax();
+ }
+ return dma_sync_wait(tx->chan, tx->cookie);
}
EXPORT_SYMBOL_GPL(dma_wait_for_async_tx);