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Date: Wed, 13 Feb 2008 00:03:03 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: linux-kernel@...r.kernel.org
Cc: hskinnemoen@...el.com, shannon.nelson@...el.com, olof@...om.net,
yur@...raft.com
Subject: [PATCH 2/4] async_tx: fix multiple dependency submission
Shrink struct dma_async_tx_descriptor and introduce
async_tx_channel_switch to properly inject a channel switch interrupt in
the descriptor stream. This simplifies the locking model as drivers no
longer need to handle dma_async_tx_descriptor.lock.
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
crypto/async_tx/async_tx.c | 197 ++++++++++++++++++++++++++++++++++++--------
drivers/dma/dmaengine.c | 2
drivers/dma/iop-adma.c | 9 +-
include/linux/dmaengine.h | 9 +-
4 files changed, 170 insertions(+), 47 deletions(-)
diff --git a/crypto/async_tx/async_tx.c b/crypto/async_tx/async_tx.c
index 2be3bae..6975616 100644
--- a/crypto/async_tx/async_tx.c
+++ b/crypto/async_tx/async_tx.c
@@ -89,13 +89,19 @@ dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx)
iter = tx;
/* find the root of the unsubmitted dependency chain */
- while (iter->cookie == -EBUSY) {
+ do {
parent = iter->parent;
- if (parent && parent->cookie == -EBUSY)
- iter = iter->parent;
- else
+ 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));
@@ -111,24 +117,33 @@ EXPORT_SYMBOL_GPL(dma_wait_for_async_tx);
void
async_tx_run_dependencies(struct dma_async_tx_descriptor *tx)
{
- struct dma_async_tx_descriptor *dep_tx, *_dep_tx;
- struct dma_device *dev;
+ struct dma_async_tx_descriptor *next = tx->next;
struct dma_chan *chan;
- list_for_each_entry_safe(dep_tx, _dep_tx, &tx->depend_list,
- depend_node) {
- chan = dep_tx->chan;
- dev = chan->device;
- /* we can't depend on ourselves */
- BUG_ON(chan == tx->chan);
- list_del(&dep_tx->depend_node);
- tx->tx_submit(dep_tx);
-
- /* we need to poke the engine as client code does not
- * know about dependency submission events
- */
- dev->device_issue_pending(chan);
+ if (!next)
+ return;
+
+ tx->next = NULL;
+ chan = next->chan;
+
+ /* keep submitting up until a channel switch is detected
+ * in that case we will be called again as a result of
+ * processing the interrupt from async_tx_channel_switch
+ */
+ while (next && next->chan == chan) {
+ struct dma_async_tx_descriptor *_next;
+
+ spin_lock_bh(&next->lock);
+ next->parent = NULL;
+ _next = next->next;
+ next->next = NULL;
+ spin_unlock_bh(&next->lock);
+
+ next->tx_submit(next);
+ next = _next;
}
+
+ chan->device->device_issue_pending(chan);
}
EXPORT_SYMBOL_GPL(async_tx_run_dependencies);
@@ -397,6 +412,92 @@ static void __exit async_tx_exit(void)
}
#endif
+
+/**
+ * async_tx_channel_switch - queue an interrupt descriptor with a dependency
+ * pre-attached.
+ * @depend_tx: the operation that must finish before the new operation runs
+ * @tx: the new operation
+ */
+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_async_tx_descriptor *intr_tx = (void *) ~0;
+
+ /* first check to see if we can still append to depend_tx */
+ spin_lock_bh(&depend_tx->lock);
+ if (depend_tx->parent && depend_tx->chan == tx->chan) {
+ tx->parent = depend_tx;
+ depend_tx->next = tx;
+ intr_tx = NULL;
+ }
+ spin_unlock_bh(&depend_tx->lock);
+
+ if (!intr_tx)
+ return;
+
+ chan = depend_tx->chan;
+ device = chan->device;
+
+ /* see if we can schedule an interrupt
+ * otherwise poll for completion
+ */
+ if (dma_has_cap(DMA_INTERRUPT, device->cap_mask))
+ intr_tx = device->device_prep_dma_interrupt(chan);
+ else
+ intr_tx = NULL;
+
+ if (intr_tx) {
+ intr_tx->callback = NULL;
+ intr_tx->callback_param = NULL;
+ tx->parent = intr_tx;
+ /* safe to set ->next outside the lock since we know we are
+ * not submitted yet
+ */
+ intr_tx->next = tx;
+
+ /* check if we need to append */
+ spin_lock_bh(&depend_tx->lock);
+ if (depend_tx->parent) {
+ intr_tx->parent = depend_tx;
+ depend_tx->next = intr_tx;
+ async_tx_ack(intr_tx);
+ intr_tx = NULL;
+ }
+ spin_unlock_bh(&depend_tx->lock);
+
+ if (intr_tx) {
+ intr_tx->parent = NULL;
+ intr_tx->tx_submit(intr_tx);
+ async_tx_ack(intr_tx);
+ }
+ } else {
+ if (dma_wait_for_async_tx(depend_tx) == DMA_ERROR)
+ panic("%s: DMA_ERROR waiting for depend_tx\n",
+ __func__);
+ tx->tx_submit(tx);
+ }
+}
+
+
+/**
+ * submit_disposition - while holding depend_tx->lock we must avoid submitting
+ * new operations to prevent a circular locking dependency with
+ * drivers that already hold a channel lock when calling
+ * async_tx_run_dependencies.
+ * @ASYNC_TX_SUBMITTED: we were able to append the new operation under the lock
+ * @ASYNC_TX_CHANNEL_SWITCH: when the lock is dropped schedule a channel switch
+ * @ASYNC_TX_DIRECT_SUBMIT: when the lock is dropped submit directly
+ */
+enum submit_disposition {
+ ASYNC_TX_SUBMITTED,
+ ASYNC_TX_CHANNEL_SWITCH,
+ ASYNC_TX_DIRECT_SUBMIT,
+};
+
void
async_tx_submit(struct dma_chan *chan, struct dma_async_tx_descriptor *tx,
enum async_tx_flags flags, struct dma_async_tx_descriptor *depend_tx,
@@ -405,28 +506,54 @@ async_tx_submit(struct dma_chan *chan, struct dma_async_tx_descriptor *tx,
tx->callback = cb_fn;
tx->callback_param = cb_param;
- /* set this new tx to run after depend_tx if:
- * 1/ a dependency exists (depend_tx is !NULL)
- * 2/ the tx can not be submitted to the current channel
- */
- if (depend_tx && depend_tx->chan != chan) {
- /* if ack is already set then we cannot be sure
+ if (depend_tx) {
+ enum submit_disposition s;
+
+ /* sanity check the dependency chain:
+ * 1/ if ack is already set then we cannot be sure
* we are referring to the correct operation
+ * 2/ dependencies are 1:1 i.e. two transactions can
+ * not depend on the same parent
*/
- BUG_ON(depend_tx->ack);
+ BUG_ON(depend_tx->ack || depend_tx->next || tx->parent);
- tx->parent = depend_tx;
+ /* the lock prevents async_tx_run_dependencies from missing
+ * the setting of ->next when ->parent != NULL
+ */
spin_lock_bh(&depend_tx->lock);
- list_add_tail(&tx->depend_node, &depend_tx->depend_list);
- if (depend_tx->cookie == 0) {
- struct dma_chan *dep_chan = depend_tx->chan;
- struct dma_device *dep_dev = dep_chan->device;
- dep_dev->device_dependency_added(dep_chan);
+ if (depend_tx->parent) {
+ /* we have a parent so we can not submit directly
+ * if we are staying on the same channel: append
+ * else: channel switch
+ */
+ if (depend_tx->chan == chan) {
+ tx->parent = depend_tx;
+ depend_tx->next = tx;
+ s = ASYNC_TX_SUBMITTED;
+ } else
+ s = ASYNC_TX_CHANNEL_SWITCH;
+ } else {
+ /* we do not have a parent so we may be able to submit
+ * directly if we are staying on the same channel
+ */
+ if (depend_tx->chan == chan)
+ s = ASYNC_TX_DIRECT_SUBMIT;
+ else
+ s = ASYNC_TX_CHANNEL_SWITCH;
}
spin_unlock_bh(&depend_tx->lock);
- /* schedule an interrupt to trigger the channel switch */
- async_trigger_callback(ASYNC_TX_ACK, depend_tx, NULL, NULL);
+ switch (s) {
+ case ASYNC_TX_SUBMITTED:
+ break;
+ case ASYNC_TX_CHANNEL_SWITCH:
+ async_tx_channel_switch(depend_tx, tx);
+ break;
+ case ASYNC_TX_DIRECT_SUBMIT:
+ tx->parent = NULL;
+ tx->tx_submit(tx);
+ break;
+ }
} else {
tx->parent = NULL;
tx->tx_submit(tx);
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 2996523..9369781 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -600,8 +600,6 @@ void dma_async_tx_descriptor_init(struct dma_async_tx_descriptor *tx,
{
tx->chan = chan;
spin_lock_init(&tx->lock);
- INIT_LIST_HEAD(&tx->depend_node);
- INIT_LIST_HEAD(&tx->depend_list);
}
EXPORT_SYMBOL(dma_async_tx_descriptor_init);
diff --git a/drivers/dma/iop-adma.c b/drivers/dma/iop-adma.c
index 3986d54..a6171da 100644
--- a/drivers/dma/iop-adma.c
+++ b/drivers/dma/iop-adma.c
@@ -63,7 +63,6 @@ iop_adma_run_tx_complete_actions(struct iop_adma_desc_slot *desc,
struct iop_adma_chan *iop_chan, dma_cookie_t cookie)
{
BUG_ON(desc->async_tx.cookie < 0);
- spin_lock_bh(&desc->async_tx.lock);
if (desc->async_tx.cookie > 0) {
cookie = desc->async_tx.cookie;
desc->async_tx.cookie = 0;
@@ -101,7 +100,6 @@ iop_adma_run_tx_complete_actions(struct iop_adma_desc_slot *desc,
/* run dependent operations */
async_tx_run_dependencies(&desc->async_tx);
- spin_unlock_bh(&desc->async_tx.lock);
return cookie;
}
@@ -275,8 +273,11 @@ iop_adma_slot_cleanup(struct iop_adma_chan *iop_chan)
static void iop_adma_tasklet(unsigned long data)
{
- struct iop_adma_chan *chan = (struct iop_adma_chan *) data;
- __iop_adma_slot_cleanup(chan);
+ struct iop_adma_chan *iop_chan = (struct iop_adma_chan *) data;
+
+ spin_lock(&iop_chan->lock);
+ __iop_adma_slot_cleanup(iop_chan);
+ spin_unlock(&iop_chan->lock);
}
static struct iop_adma_desc_slot *
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index acbb364..d04b169 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -221,11 +221,9 @@ typedef void (*dma_async_tx_callback)(void *dma_async_param);
* @callback: routine to call after this operation is complete
* @callback_param: general parameter to pass to the callback routine
* ---async_tx api specific fields---
- * @depend_list: at completion this list of transactions are submitted
- * @depend_node: allow this transaction to be executed after another
- * transaction has completed, possibly on another channel
+ * @next: at completion submit this descriptor
* @parent: pointer to the next level up in the dependency chain
- * @lock: protect the dependency list
+ * @lock: protect the parent and next pointers
*/
struct dma_async_tx_descriptor {
dma_cookie_t cookie;
@@ -236,8 +234,7 @@ struct dma_async_tx_descriptor {
dma_cookie_t (*tx_submit)(struct dma_async_tx_descriptor *tx);
dma_async_tx_callback callback;
void *callback_param;
- struct list_head depend_list;
- struct list_head depend_node;
+ struct dma_async_tx_descriptor *next;
struct dma_async_tx_descriptor *parent;
spinlock_t lock;
};
--
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