ioatdma: fix race between updating ioat->head and IOAT_COMPLETION_PENDING
There is a race that can hit during __cleanup() when the ioat->head pointer is
incremented during descriptor submission. The __cleanup() can clear the
PENDING flag when it does not see any active descriptors. This causes new
submitted descriptors to be ignored because the COMPLETION_PENDING flag is
cleared. This was introduced when code was adapted from ioatdma v1 to ioatdma
v2. For v2 and v3, IOAT_COMPLETION_PENDING flag will be abandoned and a new
flag IOAT_CHAN_ACTIVE will be utilized. This flag will also be protected under
the prep_lock when being modified in order to avoid the race.
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Dan Williams <djbw@fb.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
diff --git a/drivers/dma/ioat/dma_v3.c b/drivers/dma/ioat/dma_v3.c
index e52cf1e..570dd63 100644
--- a/drivers/dma/ioat/dma_v3.c
+++ b/drivers/dma/ioat/dma_v3.c
@@ -342,61 +342,22 @@
__ioat2_restart_chan(ioat);
}
-static void ioat3_timer_event(unsigned long data)
+static void check_active(struct ioat2_dma_chan *ioat)
{
- struct ioat2_dma_chan *ioat = to_ioat2_chan((void *) data);
struct ioat_chan_common *chan = &ioat->base;
- if (test_bit(IOAT_COMPLETION_PENDING, &chan->state)) {
- dma_addr_t phys_complete;
- u64 status;
+ if (ioat2_ring_active(ioat)) {
+ mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
+ return;
+ }
- status = ioat_chansts(chan);
-
- /* when halted due to errors check for channel
- * programming errors before advancing the completion state
- */
- if (is_ioat_halted(status)) {
- u32 chanerr;
-
- chanerr = readl(chan->reg_base + IOAT_CHANERR_OFFSET);
- dev_err(to_dev(chan), "%s: Channel halted (%x)\n",
- __func__, chanerr);
- if (test_bit(IOAT_RUN, &chan->state))
- BUG_ON(is_ioat_bug(chanerr));
- else /* we never got off the ground */
- return;
- }
-
- /* if we haven't made progress and we have already
- * acknowledged a pending completion once, then be more
- * forceful with a restart
- */
- 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)) {
- spin_lock_bh(&ioat->prep_lock);
- ioat3_restart_channel(ioat);
- spin_unlock_bh(&ioat->prep_lock);
- } else {
- set_bit(IOAT_COMPLETION_ACK, &chan->state);
- mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
- }
- spin_unlock_bh(&chan->cleanup_lock);
- } else {
- u16 active;
-
+ if (test_and_clear_bit(IOAT_CHAN_ACTIVE, &chan->state))
+ mod_timer(&chan->timer, jiffies + IDLE_TIMEOUT);
+ else if (ioat->alloc_order > ioat_get_alloc_order()) {
/* if the ring is idle, empty, and oversized try to step
* down the size
*/
- 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->prep_lock);
- spin_unlock_bh(&chan->cleanup_lock);
+ reshape_ring(ioat, ioat->alloc_order - 1);
/* keep shrinking until we get back to our minimum
* default size
@@ -404,6 +365,60 @@
if (ioat->alloc_order > ioat_get_alloc_order())
mod_timer(&chan->timer, jiffies + IDLE_TIMEOUT);
}
+
+}
+
+void ioat3_timer_event(unsigned long data)
+{
+ struct ioat2_dma_chan *ioat = to_ioat2_chan((void *) data);
+ struct ioat_chan_common *chan = &ioat->base;
+ dma_addr_t phys_complete;
+ u64 status;
+
+ status = ioat_chansts(chan);
+
+ /* when halted due to errors check for channel
+ * programming errors before advancing the completion state
+ */
+ if (is_ioat_halted(status)) {
+ u32 chanerr;
+
+ chanerr = readl(chan->reg_base + IOAT_CHANERR_OFFSET);
+ dev_err(to_dev(chan), "%s: Channel halted (%x)\n",
+ __func__, chanerr);
+ if (test_bit(IOAT_RUN, &chan->state))
+ BUG_ON(is_ioat_bug(chanerr));
+ else /* we never got off the ground */
+ return;
+ }
+
+ /* if we haven't made progress and we have already
+ * acknowledged a pending completion once, then be more
+ * forceful with a restart
+ */
+ 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)) {
+ spin_lock_bh(&ioat->prep_lock);
+ ioat3_restart_channel(ioat);
+ spin_unlock_bh(&ioat->prep_lock);
+ spin_unlock_bh(&chan->cleanup_lock);
+ return;
+ } else {
+ set_bit(IOAT_COMPLETION_ACK, &chan->state);
+ mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
+ }
+
+
+ if (ioat2_ring_active(ioat))
+ mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
+ else {
+ spin_lock_bh(&ioat->prep_lock);
+ check_active(ioat);
+ spin_unlock_bh(&ioat->prep_lock);
+ }
+ spin_unlock_bh(&chan->cleanup_lock);
}
static enum dma_status