Commit 1c51099a authored Nov 10, 2014 by Oded Gabbay Committed by Joerg Roedel Nov 12, 2014

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>

parent 206c5f60

drivers/iommu/amd_iommu_v2.c

+2 −6

Original line number	Diff line number	Diff line
		@@ -279,11 +279,9 @@ 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);