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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>
hifive-unleashed-5.1
Oded Gabbay 2014-11-10 10:57:36 +02:00
parent e7cc3dd48c
commit a015c1e926
1 changed files with 2 additions and 6 deletions
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8
drivers/iommu/amd_iommu_v2.c
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@ -272,10 +272,8 @@ 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)
@ -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);