ioat: fix tasklet tear down

Since commit 77873803363c "net_dma: mark broken" we no longer pin dma
engines active for the network-receive-offload use case.  As a result
the ->free_chan_resources() that occurs after the driver self test no
longer has a NET_DMA induced ->alloc_chan_resources() to back it up.  A
late firing irq can lead to ksoftirqd spinning indefinitely due to the
tasklet_disable() performed by ->free_chan_resources().  Only
->alloc_chan_resources() can clear this condition in affected kernels.

This problem has been present since commit 3e037454bcfa "I/OAT: Add
support for MSI and MSI-X" in 2.6.24, but is now exposed. Given the
NET_DMA use case is deprecated we can revisit moving the driver to use
threaded irqs.  For now, just tear down the irq and tasklet properly by:

1/ Disable the irq from triggering the tasklet

2/ Disable the irq from re-arming

3/ Flush inflight interrupts

4/ Flush the timer

5/ Flush inflight tasklets

References:
https://lkml.org/lkml/2014/1/27/282
https://lkml.org/lkml/2014/2/19/672

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: <stable@vger.kernel.org>
Reported-by: Mike Galbraith <bitbucket@online.de>
Reported-by: Stanislav Fomichev <stfomichev@yandex-team.ru>
Tested-by: Mike Galbraith <bitbucket@online.de>
Tested-by: Stanislav Fomichev <stfomichev@yandex-team.ru>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

4 files changed, 54 insertions, 13 deletions

diff --git a/drivers/dma/ioat/dma.c b/drivers/dma/ioat/dma.c
index 87529181efcc..4e3549a16132 100644
--- a/drivers/dma/ioat/dma.c
+++ b/drivers/dma/ioat/dma.c
@@ -77,7 +77,8 @@ static irqreturn_t ioat_dma_do_interrupt(int irq, void *data)
         attnstatus = readl(instance->reg_base + IOAT_ATTNSTATUS_OFFSET);
         for_each_set_bit(bit, &attnstatus, BITS_PER_LONG) {
                 chan = ioat_chan_by_index(instance, bit);
-                tasklet_schedule(&chan->cleanup_task);
+                if (test_bit(IOAT_RUN, &chan->state))
+                        tasklet_schedule(&chan->cleanup_task);
         }
 
         writeb(intrctrl, instance->reg_base + IOAT_INTRCTRL_OFFSET);
@@ -93,7 +94,8 @@ static irqreturn_t ioat_dma_do_interrupt_msix(int irq, void *data)
 {
         struct ioat_chan_common *chan = data;
 
-        tasklet_schedule(&chan->cleanup_task);
+        if (test_bit(IOAT_RUN, &chan->state))
+                tasklet_schedule(&chan->cleanup_task);
 
         return IRQ_HANDLED;
 }
@@ -116,7 +118,6 @@ void ioat_init_channel(struct ioatdma_device *device, struct ioat_chan_common *c
         chan->timer.function = device->timer_fn;
         chan->timer.data = data;
         tasklet_init(&chan->cleanup_task, device->cleanup_fn, data);
-        tasklet_disable(&chan->cleanup_task);
 }
 
 /**
@@ -354,13 +355,49 @@ static int ioat1_dma_alloc_chan_resources(struct dma_chan *c)
         writel(((u64) chan->completion_dma) >> 32,
                chan->reg_base + IOAT_CHANCMP_OFFSET_HIGH);
 
-        tasklet_enable(&chan->cleanup_task);
+        set_bit(IOAT_RUN, &chan->state);
         ioat1_dma_start_null_desc(ioat);  /* give chain to dma device */
         dev_dbg(to_dev(chan), "%s: allocated %d descriptors\n",
                 __func__, ioat->desccount);
         return ioat->desccount;
 }
 
+void ioat_stop(struct ioat_chan_common *chan)
+{
+        struct ioatdma_device *device = chan->device;
+        struct pci_dev *pdev = device->pdev;
+        int chan_id = chan_num(chan);
+        struct msix_entry *msix;
+
+        /* 1/ stop irq from firing tasklets
+         * 2/ stop the tasklet from re-arming irqs
+         */
+        clear_bit(IOAT_RUN, &chan->state);
+
+        /* flush inflight interrupts */
+        switch (device->irq_mode) {
+        case IOAT_MSIX:
+                msix = &device->msix_entries[chan_id];
+                synchronize_irq(msix->vector);
+                break;
+        case IOAT_MSI:
+        case IOAT_INTX:
+                synchronize_irq(pdev->irq);
+                break;
+        default:
+                break;
+        }
+
+        /* flush inflight timers */
+        del_timer_sync(&chan->timer);
+
+        /* flush inflight tasklet runs */
+        tasklet_kill(&chan->cleanup_task);
+
+        /* final cleanup now that everything is quiesced and can't re-arm */
+        device->cleanup_fn((unsigned long) &chan->common);
+}
+
 /**
  * ioat1_dma_free_chan_resources - release all the descriptors
  * @chan: the channel to be cleaned
@@ -379,9 +416,7 @@ static void ioat1_dma_free_chan_resources(struct dma_chan *c)
         if (ioat->desccount == 0)
                 return;
 
-        tasklet_disable(&chan->cleanup_task);
-        del_timer_sync(&chan->timer);
-        ioat1_cleanup(ioat);
+        ioat_stop(chan);
 
         /* Delay 100ms after reset to allow internal DMA logic to quiesce
          * before removing DMA descriptor resources.
@@ -526,8 +561,11 @@ ioat1_dma_prep_memcpy(struct dma_chan *c, dma_addr_t dma_dest,
 static void ioat1_cleanup_event(unsigned long data)
 {
         struct ioat_dma_chan *ioat = to_ioat_chan((void *) data);
+        struct ioat_chan_common *chan = &ioat->base;
 
         ioat1_cleanup(ioat);
+        if (!test_bit(IOAT_RUN, &chan->state))
+                return;
         writew(IOAT_CHANCTRL_RUN, ioat->base.reg_base + IOAT_CHANCTRL_OFFSET);
 }
 
diff --git a/drivers/dma/ioat/dma.h b/drivers/dma/ioat/dma.h
index 11fb877ddca9..e982f00a9843 100644
--- a/drivers/dma/ioat/dma.h
+++ b/drivers/dma/ioat/dma.h
@@ -356,6 +356,7 @@ bool ioat_cleanup_preamble(struct ioat_chan_common *chan,
 void ioat_kobject_add(struct ioatdma_device *device, struct kobj_type *type);
 void ioat_kobject_del(struct ioatdma_device *device);
 int ioat_dma_setup_interrupts(struct ioatdma_device *device);
+void ioat_stop(struct ioat_chan_common *chan);
 extern const struct sysfs_ops ioat_sysfs_ops;
 extern struct ioat_sysfs_entry ioat_version_attr;
 extern struct ioat_sysfs_entry ioat_cap_attr;
diff --git a/drivers/dma/ioat/dma_v2.c b/drivers/dma/ioat/dma_v2.c
index 5d3affe7e976..8d1058085eeb 100644
--- a/drivers/dma/ioat/dma_v2.c
+++ b/drivers/dma/ioat/dma_v2.c
@@ -190,8 +190,11 @@ static void ioat2_cleanup(struct ioat2_dma_chan *ioat)
 void ioat2_cleanup_event(unsigned long data)
 {
         struct ioat2_dma_chan *ioat = to_ioat2_chan((void *) data);
+        struct ioat_chan_common *chan = &ioat->base;
 
         ioat2_cleanup(ioat);
+        if (!test_bit(IOAT_RUN, &chan->state))
+                return;
         writew(IOAT_CHANCTRL_RUN, ioat->base.reg_base + IOAT_CHANCTRL_OFFSET);
 }
 
@@ -553,10 +556,10 @@ int ioat2_alloc_chan_resources(struct dma_chan *c)
         ioat->issued = 0;
         ioat->tail = 0;
         ioat->alloc_order = order;
+        set_bit(IOAT_RUN, &chan->state);
         spin_unlock_bh(&ioat->prep_lock);
         spin_unlock_bh(&chan->cleanup_lock);
 
-        tasklet_enable(&chan->cleanup_task);
         ioat2_start_null_desc(ioat);
 
         /* check that we got off the ground */
@@ -566,7 +569,6 @@ int ioat2_alloc_chan_resources(struct dma_chan *c)
         } while (i++ < 20 && !is_ioat_active(status) && !is_ioat_idle(status));
 
         if (is_ioat_active(status) || is_ioat_idle(status)) {
-                set_bit(IOAT_RUN, &chan->state);
                 return 1 << ioat->alloc_order;
         } else {
                 u32 chanerr = readl(chan->reg_base + IOAT_CHANERR_OFFSET);
@@ -809,11 +811,8 @@ void ioat2_free_chan_resources(struct dma_chan *c)
         if (!ioat->ring)
                 return;
 
-        tasklet_disable(&chan->cleanup_task);
-        del_timer_sync(&chan->timer);
-        device->cleanup_fn((unsigned long) c);
+        ioat_stop(chan);
         device->reset_hw(chan);
-        clear_bit(IOAT_RUN, &chan->state);
 
         spin_lock_bh(&chan->cleanup_lock);
         spin_lock_bh(&ioat->prep_lock);
diff --git a/drivers/dma/ioat/dma_v3.c b/drivers/dma/ioat/dma_v3.c
index 820817e97e62..b9b38a1cf92f 100644
--- a/drivers/dma/ioat/dma_v3.c
+++ b/drivers/dma/ioat/dma_v3.c
@@ -464,8 +464,11 @@ static void ioat3_cleanup(struct ioat2_dma_chan *ioat)
 static void ioat3_cleanup_event(unsigned long data)
 {
         struct ioat2_dma_chan *ioat = to_ioat2_chan((void *) data);
+        struct ioat_chan_common *chan = &ioat->base;
 
         ioat3_cleanup(ioat);
+        if (!test_bit(IOAT_RUN, &chan->state))
+                return;
         writew(IOAT_CHANCTRL_RUN, ioat->base.reg_base + IOAT_CHANCTRL_OFFSET);
 }