Commit a015c1e9 authored Nov 10, 2014 by Oded Gabbay

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>

parent e7cc3dd4

drivers/iommu/amd_iommu_v2.c

+2 −6

Original line number	Diff line number	Diff line
		@@ -272,11 +272,9 @@ 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)
		{
		@@ -284,9 +282,7 @@ 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);