iommu/amd: Fix accounting of device_state

This patch fixes a bug in the accounting of the
device_state.  In the current code, the device_state was put
(decremented) too many times, which sometimes lead to the
driver getting stuck permanently in put_device_state_wait().
That happen because the device_state->count would go below
zero, which is never supposed to happen.

The root cause is that the device_state was decremented in
put_pasid_state() and put_pasid_state_wait() but also in all
the functions that call those functions. Therefore, the
device_state was decremented twice in each of these code
paths.

The fix is to decouple the device_state accounting from the
pasid_state accounting - remove the call to
put_device_state() from the put_pasid_state() and the
put_pasid_state_wait())

Signed-off-by: Oded Gabbay <oded.gabbay@amd.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/amd_iommu_v2.c b/drivers/iommu/amd_iommu_v2.c
index 90d734bbf467a2cec462282191f64c8f2131c1ae..a2d87a60c27f1c8d2c91264690b036b4c7174f5b 100644 (file)
--- a/drivers/iommu/amd_iommu_v2.c
+++ b/drivers/iommu/amd_iommu_v2.c
@@ -279,10 +279,8 @@ static void free_pasid_state(struct pasid_state *pasid_state)
 
 static void put_pasid_state(struct pasid_state *pasid_state)
 {
-       if (atomic_dec_and_test(&pasid_state->count)) {
-               put_device_state(pasid_state->device_state);
+       if (atomic_dec_and_test(&pasid_state->count))
                wake_up(&pasid_state->wq);
-       }
 }
 
 static void put_pasid_state_wait(struct pasid_state *pasid_state)
@@ -291,9 +289,7 @@ static void put_pasid_state_wait(struct pasid_state *pasid_state)
 
        prepare_to_wait(&pasid_state->wq, &wait, TASK_UNINTERRUPTIBLE);
 
-       if (atomic_dec_and_test(&pasid_state->count))
-               put_device_state(pasid_state->device_state);
-       else
+       if (!atomic_dec_and_test(&pasid_state->count))
                schedule();
 
        finish_wait(&pasid_state->wq, &wait);