ioat2,3: convert to producer/consumer locking
Use separate locks for the descriptor prep (producer) and descriptor
cleanup (consumer) paths. Allows the producer path to run concurrently
with the cleanup path. Inspired by Documentation/circular-buffer.txt.
Cc: David Howells <dhowells@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Maciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/drivers/dma/ioat/dma_v2.c b/drivers/dma/ioat/dma_v2.c
index b6699a3..e75d029 100644
--- a/drivers/dma/ioat/dma_v2.c
+++ b/drivers/dma/ioat/dma_v2.c
@@ -56,8 +56,6 @@
ioat->dmacount += ioat2_ring_pending(ioat);
ioat->issued = ioat->head;
- /* make descriptor updates globally visible before notifying channel */
- wmb();
writew(ioat->dmacount, chan->reg_base + IOAT_CHAN_DMACOUNT_OFFSET);
dev_dbg(to_dev(chan),
"%s: head: %#x tail: %#x issued: %#x count: %#x\n",
@@ -69,9 +67,9 @@
struct ioat2_dma_chan *ioat = to_ioat2_chan(c);
if (ioat2_ring_pending(ioat)) {
- spin_lock_bh(&ioat->ring_lock);
+ spin_lock_bh(&ioat->prep_lock);
__ioat2_issue_pending(ioat);
- spin_unlock_bh(&ioat->ring_lock);
+ spin_unlock_bh(&ioat->prep_lock);
}
}
@@ -80,7 +78,7 @@
* @ioat: ioat2+ channel
*
* Check if the number of unsubmitted descriptors has exceeded the
- * watermark. Called with ring_lock held
+ * watermark. Called with prep_lock held
*/
static void ioat2_update_pending(struct ioat2_dma_chan *ioat)
{
@@ -92,7 +90,6 @@
{
struct ioat_ring_ent *desc;
struct ioat_dma_descriptor *hw;
- int idx;
if (ioat2_ring_space(ioat) < 1) {
dev_err(to_dev(&ioat->base),
@@ -102,8 +99,7 @@
dev_dbg(to_dev(&ioat->base), "%s: head: %#x tail: %#x issued: %#x\n",
__func__, ioat->head, ioat->tail, ioat->issued);
- idx = ioat2_desc_alloc(ioat, 1);
- desc = ioat2_get_ring_ent(ioat, idx);
+ desc = ioat2_get_ring_ent(ioat, ioat->head);
hw = desc->hw;
hw->ctl = 0;
@@ -117,14 +113,16 @@
async_tx_ack(&desc->txd);
ioat2_set_chainaddr(ioat, desc->txd.phys);
dump_desc_dbg(ioat, desc);
+ wmb();
+ ioat->head += 1;
__ioat2_issue_pending(ioat);
}
static void ioat2_start_null_desc(struct ioat2_dma_chan *ioat)
{
- spin_lock_bh(&ioat->ring_lock);
+ spin_lock_bh(&ioat->prep_lock);
__ioat2_start_null_desc(ioat);
- spin_unlock_bh(&ioat->ring_lock);
+ spin_unlock_bh(&ioat->prep_lock);
}
static void __cleanup(struct ioat2_dma_chan *ioat, unsigned long phys_complete)
@@ -134,15 +132,16 @@
struct ioat_ring_ent *desc;
bool seen_current = false;
u16 active;
- int i;
+ int idx = ioat->tail, i;
dev_dbg(to_dev(chan), "%s: head: %#x tail: %#x issued: %#x\n",
__func__, ioat->head, ioat->tail, ioat->issued);
active = ioat2_ring_active(ioat);
for (i = 0; i < active && !seen_current; i++) {
- prefetch(ioat2_get_ring_ent(ioat, ioat->tail + i + 1));
- desc = ioat2_get_ring_ent(ioat, ioat->tail + i);
+ smp_read_barrier_depends();
+ prefetch(ioat2_get_ring_ent(ioat, idx + i + 1));
+ desc = ioat2_get_ring_ent(ioat, idx + i);
tx = &desc->txd;
dump_desc_dbg(ioat, desc);
if (tx->cookie) {
@@ -158,11 +157,12 @@
if (tx->phys == phys_complete)
seen_current = true;
}
- ioat->tail += i;
+ smp_mb(); /* finish all descriptor reads before incrementing tail */
+ ioat->tail = idx + i;
BUG_ON(active && !seen_current); /* no active descs have written a completion? */
chan->last_completion = phys_complete;
- if (ioat->head == ioat->tail) {
+ if (active - i == 0) {
dev_dbg(to_dev(chan), "%s: cancel completion timeout\n",
__func__);
clear_bit(IOAT_COMPLETION_PENDING, &chan->state);
@@ -179,24 +179,9 @@
struct ioat_chan_common *chan = &ioat->base;
unsigned long phys_complete;
- prefetch(chan->completion);
-
- if (!spin_trylock_bh(&chan->cleanup_lock))
- return;
-
- if (!ioat_cleanup_preamble(chan, &phys_complete)) {
- spin_unlock_bh(&chan->cleanup_lock);
- return;
- }
-
- if (!spin_trylock_bh(&ioat->ring_lock)) {
- spin_unlock_bh(&chan->cleanup_lock);
- return;
- }
-
- __cleanup(ioat, phys_complete);
-
- spin_unlock_bh(&ioat->ring_lock);
+ spin_lock_bh(&chan->cleanup_lock);
+ if (ioat_cleanup_preamble(chan, &phys_complete))
+ __cleanup(ioat, phys_complete);
spin_unlock_bh(&chan->cleanup_lock);
}
@@ -287,12 +272,10 @@
struct ioat2_dma_chan *ioat = to_ioat2_chan((void *) data);
struct ioat_chan_common *chan = &ioat->base;
- spin_lock_bh(&chan->cleanup_lock);
if (test_bit(IOAT_COMPLETION_PENDING, &chan->state)) {
unsigned long phys_complete;
u64 status;
- spin_lock_bh(&ioat->ring_lock);
status = ioat_chansts(chan);
/* when halted due to errors check for channel
@@ -311,26 +294,31 @@
* acknowledged a pending completion once, then be more
* forceful with a restart
*/
- if (ioat_cleanup_preamble(chan, &phys_complete))
+ spin_lock_bh(&chan->cleanup_lock);
+ if (ioat_cleanup_preamble(chan, &phys_complete)) {
__cleanup(ioat, phys_complete);
- else if (test_bit(IOAT_COMPLETION_ACK, &chan->state))
+ } else if (test_bit(IOAT_COMPLETION_ACK, &chan->state)) {
+ spin_lock_bh(&ioat->prep_lock);
ioat2_restart_channel(ioat);
- else {
+ spin_unlock_bh(&ioat->prep_lock);
+ } else {
set_bit(IOAT_COMPLETION_ACK, &chan->state);
mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
}
- spin_unlock_bh(&ioat->ring_lock);
+ spin_unlock_bh(&chan->cleanup_lock);
} else {
u16 active;
/* if the ring is idle, empty, and oversized try to step
* down the size
*/
- spin_lock_bh(&ioat->ring_lock);
+ spin_lock_bh(&chan->cleanup_lock);
+ spin_lock_bh(&ioat->prep_lock);
active = ioat2_ring_active(ioat);
if (active == 0 && ioat->alloc_order > ioat_get_alloc_order())
reshape_ring(ioat, ioat->alloc_order-1);
- spin_unlock_bh(&ioat->ring_lock);
+ spin_unlock_bh(&ioat->prep_lock);
+ spin_unlock_bh(&chan->cleanup_lock);
/* keep shrinking until we get back to our minimum
* default size
@@ -338,7 +326,6 @@
if (ioat->alloc_order > ioat_get_alloc_order())
mod_timer(&chan->timer, jiffies + IDLE_TIMEOUT);
}
- spin_unlock_bh(&chan->cleanup_lock);
}
static int ioat2_reset_hw(struct ioat_chan_common *chan)
@@ -392,7 +379,7 @@
ioat_init_channel(device, &ioat->base, i);
ioat->xfercap_log = xfercap_log;
- spin_lock_init(&ioat->ring_lock);
+ spin_lock_init(&ioat->prep_lock);
if (device->reset_hw(&ioat->base)) {
i = 0;
break;
@@ -418,8 +405,17 @@
if (!test_and_set_bit(IOAT_COMPLETION_PENDING, &chan->state))
mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
+
+ /* make descriptor updates visible before advancing ioat->head,
+ * this is purposefully not smp_wmb() since we are also
+ * publishing the descriptor updates to a dma device
+ */
+ wmb();
+
+ ioat->head += ioat->produce;
+
ioat2_update_pending(ioat);
- spin_unlock_bh(&ioat->ring_lock);
+ spin_unlock_bh(&ioat->prep_lock);
return cookie;
}
@@ -531,13 +527,15 @@
if (!ring)
return -ENOMEM;
- spin_lock_bh(&ioat->ring_lock);
+ spin_lock_bh(&chan->cleanup_lock);
+ spin_lock_bh(&ioat->prep_lock);
ioat->ring = ring;
ioat->head = 0;
ioat->issued = 0;
ioat->tail = 0;
ioat->alloc_order = order;
- spin_unlock_bh(&ioat->ring_lock);
+ spin_unlock_bh(&ioat->prep_lock);
+ spin_unlock_bh(&chan->cleanup_lock);
tasklet_enable(&chan->cleanup_task);
ioat2_start_null_desc(ioat);
@@ -653,54 +651,61 @@
}
/**
- * ioat2_alloc_and_lock - common descriptor alloc boilerplate for ioat2,3 ops
- * @idx: gets starting descriptor index on successful allocation
+ * ioat2_check_space_lock - verify space and grab ring producer lock
* @ioat: ioat2,3 channel (ring) to operate on
* @num_descs: allocation length
*/
-int ioat2_alloc_and_lock(u16 *idx, struct ioat2_dma_chan *ioat, int num_descs)
+int ioat2_check_space_lock(struct ioat2_dma_chan *ioat, int num_descs)
{
struct ioat_chan_common *chan = &ioat->base;
+ bool retry;
- spin_lock_bh(&ioat->ring_lock);
+ retry:
+ spin_lock_bh(&ioat->prep_lock);
/* never allow the last descriptor to be consumed, we need at
* least one free at all times to allow for on-the-fly ring
* resizing.
*/
- while (unlikely(ioat2_ring_space(ioat) <= num_descs)) {
- if (reshape_ring(ioat, ioat->alloc_order + 1) &&
- ioat2_ring_space(ioat) > num_descs)
- break;
+ if (likely(ioat2_ring_space(ioat) > num_descs)) {
+ dev_dbg(to_dev(chan), "%s: num_descs: %d (%x:%x:%x)\n",
+ __func__, num_descs, ioat->head, ioat->tail, ioat->issued);
+ ioat->produce = num_descs;
+ return 0; /* with ioat->prep_lock held */
+ }
+ retry = test_and_set_bit(IOAT_RESHAPE_PENDING, &chan->state);
+ spin_unlock_bh(&ioat->prep_lock);
- if (printk_ratelimit())
- dev_dbg(to_dev(chan),
- "%s: ring full! num_descs: %d (%x:%x:%x)\n",
- __func__, num_descs, ioat->head, ioat->tail,
- ioat->issued);
- spin_unlock_bh(&ioat->ring_lock);
+ /* is another cpu already trying to expand the ring? */
+ if (retry)
+ goto retry;
- /* progress reclaim in the allocation failure case we
- * may be called under bh_disabled so we need to trigger
- * the timer event directly
- */
- spin_lock_bh(&chan->cleanup_lock);
- if (jiffies > chan->timer.expires &&
- timer_pending(&chan->timer)) {
- struct ioatdma_device *device = chan->device;
+ spin_lock_bh(&chan->cleanup_lock);
+ spin_lock_bh(&ioat->prep_lock);
+ retry = reshape_ring(ioat, ioat->alloc_order + 1);
+ clear_bit(IOAT_RESHAPE_PENDING, &chan->state);
+ spin_unlock_bh(&ioat->prep_lock);
+ spin_unlock_bh(&chan->cleanup_lock);
- mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
- spin_unlock_bh(&chan->cleanup_lock);
- device->timer_fn((unsigned long) &chan->common);
- } else
- spin_unlock_bh(&chan->cleanup_lock);
- return -ENOMEM;
+ /* if we were able to expand the ring retry the allocation */
+ if (retry)
+ goto retry;
+
+ if (printk_ratelimit())
+ dev_dbg(to_dev(chan), "%s: ring full! num_descs: %d (%x:%x:%x)\n",
+ __func__, num_descs, ioat->head, ioat->tail, ioat->issued);
+
+ /* progress reclaim in the allocation failure case we may be
+ * called under bh_disabled so we need to trigger the timer
+ * event directly
+ */
+ if (jiffies > chan->timer.expires && timer_pending(&chan->timer)) {
+ struct ioatdma_device *device = chan->device;
+
+ mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
+ device->timer_fn((unsigned long) &chan->common);
}
- dev_dbg(to_dev(chan), "%s: num_descs: %d (%x:%x:%x)\n",
- __func__, num_descs, ioat->head, ioat->tail, ioat->issued);
-
- *idx = ioat2_desc_alloc(ioat, num_descs);
- return 0; /* with ioat->ring_lock held */
+ return -ENOMEM;
}
struct dma_async_tx_descriptor *
@@ -713,14 +718,11 @@
dma_addr_t dst = dma_dest;
dma_addr_t src = dma_src;
size_t total_len = len;
- int num_descs;
- u16 idx;
- int i;
+ int num_descs, idx, i;
num_descs = ioat2_xferlen_to_descs(ioat, len);
- if (likely(num_descs) &&
- ioat2_alloc_and_lock(&idx, ioat, num_descs) == 0)
- /* pass */;
+ if (likely(num_descs) && ioat2_check_space_lock(ioat, num_descs) == 0)
+ idx = ioat->head;
else
return NULL;
i = 0;
@@ -777,7 +779,8 @@
device->cleanup_fn((unsigned long) c);
device->reset_hw(chan);
- spin_lock_bh(&ioat->ring_lock);
+ spin_lock_bh(&chan->cleanup_lock);
+ spin_lock_bh(&ioat->prep_lock);
descs = ioat2_ring_space(ioat);
dev_dbg(to_dev(chan), "freeing %d idle descriptors\n", descs);
for (i = 0; i < descs; i++) {
@@ -800,7 +803,8 @@
ioat->alloc_order = 0;
pci_pool_free(device->completion_pool, chan->completion,
chan->completion_dma);
- spin_unlock_bh(&ioat->ring_lock);
+ spin_unlock_bh(&ioat->prep_lock);
+ spin_unlock_bh(&chan->cleanup_lock);
chan->last_completion = 0;
chan->completion_dma = 0;