On Tue, Feb 03, 2015 at 12:27:33PM +0100, Peter Zijlstra wrote:
> drivers/iommu/amd_iommu_v2.c-static void put_device_state_wait(struct
> device_state *dev_state)
> drivers/iommu/amd_iommu_v2.c-{
> drivers/iommu/amd_iommu_v2.c- DEFINE_WAIT(wait);
> drivers/iommu/amd_iommu_v2.c-
> drivers/iommu/amd_iommu_v2.c- prepare_to_wait(&dev_state->wq, &wait,
> TASK_UNINTERRUPTIBLE);
> drivers/iommu/amd_iommu_v2.c- if (!atomic_dec_and_test(&dev_state->count))
> drivers/iommu/amd_iommu_v2.c: schedule();
> drivers/iommu/amd_iommu_v2.c- finish_wait(&dev_state->wq, &wait);
> drivers/iommu/amd_iommu_v2.c-
> drivers/iommu/amd_iommu_v2.c- free_device_state(dev_state);
> drivers/iommu/amd_iommu_v2.c-}
>
> No loop...
Jesse, any objections to this?
---
Subject: iommu/amd: Fix amd_iommu_free_device()
put_device_state_wait() doesn't loop on the condition and a spurious
wakeup will have it free the device state even though there might still
be references out to it.
Fix this by using 'normal' wait primitives.
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
---
drivers/iommu/amd_iommu_v2.c | 20 +++++++-------------
1 file changed, 7 insertions(+), 13 deletions(-)
diff --git a/drivers/iommu/amd_iommu_v2.c b/drivers/iommu/amd_iommu_v2.c
index 90f70d0e1141..b6398d7285f7 100644
--- a/drivers/iommu/amd_iommu_v2.c
+++ b/drivers/iommu/amd_iommu_v2.c
@@ -151,18 +151,6 @@ static void put_device_state(struct device_state
*dev_state)
wake_up(&dev_state->wq);
}
-static void put_device_state_wait(struct device_state *dev_state)
-{
- DEFINE_WAIT(wait);
-
- prepare_to_wait(&dev_state->wq, &wait, TASK_UNINTERRUPTIBLE);
- if (!atomic_dec_and_test(&dev_state->count))
- schedule();
- finish_wait(&dev_state->wq, &wait);
-
- free_device_state(dev_state);
-}
-
/* Must be called under dev_state->lock */
static struct pasid_state **__get_pasid_state_ptr(struct device_state
*dev_state,
int pasid, bool alloc)
@@ -851,7 +839,13 @@ void amd_iommu_free_device(struct pci_dev *pdev)
/* Get rid of any remaining pasid states */
free_pasid_states(dev_state);
- put_device_state_wait(dev_state);
+ put_device_state(dev_state);
+ /*
+ * Wait until the last reference is dropped before freeing
+ * the device state.
+ */
+ wait_event(dev_state->wq, !atomic_read(&dev_state->count));
+ free_device_state(dev_state);
}
EXPORT_SYMBOL(amd_iommu_free_device);
--
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