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.h b/drivers/dma/ioat/dma.h
index 5e8fe01..1020598 100644 (file)
--- a/drivers/dma/ioat/dma.h
+++ b/drivers/dma/ioat/dma.h
@@ -97,6 +97,7 @@ struct ioat_chan_common {
        #define IOAT_KOBJ_INIT_FAIL 3
        #define IOAT_RESHAPE_PENDING 4
        #define IOAT_RUN 5
+       #define IOAT_CHAN_ACTIVE 6
        struct timer_list timer;
        #define COMPLETION_TIMEOUT msecs_to_jiffies(100)
        #define IDLE_TIMEOUT msecs_to_jiffies(2000)

diff --git a/drivers/dma/ioat/dma_v2.c b/drivers/dma/ioat/dma_v2.c
index b9d6678..e2b2c70 100644 (file)
--- a/drivers/dma/ioat/dma_v2.c
+++ b/drivers/dma/ioat/dma_v2.c
@@ -269,61 +269,22 @@ static void ioat2_restart_channel(struct ioat2_dma_chan *ioat)
        __ioat2_restart_chan(ioat);
 }
 
-void ioat2_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;
-
-               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);
-                       ioat2_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 (ioat2_ring_active(ioat)) {
+               mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
+               return;
+       }
 
+       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
@@ -331,6 +292,60 @@ void ioat2_timer_event(unsigned long data)
                if (ioat->alloc_order > ioat_get_alloc_order())
                        mod_timer(&chan->timer, jiffies + IDLE_TIMEOUT);
        }
+
+}
+
+void ioat2_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);
+               ioat2_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 int ioat2_reset_hw(struct ioat_chan_common *chan)
@@ -404,7 +419,7 @@ static dma_cookie_t ioat2_tx_submit_unlock(struct dma_async_tx_descriptor *tx)
        cookie = dma_cookie_assign(tx);
        dev_dbg(to_dev(&ioat->base), "%s: cookie: %d\n", __func__, cookie);
 
-       if (!test_and_set_bit(IOAT_COMPLETION_PENDING, &chan->state))
+       if (!test_and_set_bit(IOAT_CHAN_ACTIVE, &chan->state))
                mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
 
        /* make descriptor updates visible before advancing ioat->head,

diff --git a/drivers/dma/ioat/dma_v3.c b/drivers/dma/ioat/dma_v3.c
index e52cf1e..570dd63 100644 (file)
--- a/drivers/dma/ioat/dma_v3.c
+++ b/drivers/dma/ioat/dma_v3.c
@@ -342,61 +342,22 @@ static void ioat3_restart_channel(struct ioat2_dma_chan *ioat)
        __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;
-
-               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 (ioat2_ring_active(ioat)) {
+               mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
+               return;
+       }
 
+       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 @@ static void ioat3_timer_event(unsigned long data)
                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