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Subject[PATCH v2] iommu/amd: Use wait_event in put_pasid_state_wait
On Wed, Feb 04, 2015 at 05:34:50PM +0100, Peter Zijlstra wrote:
> You just lost your atomic_dec.

So this should be the correct version then.

From 2a52250e542d8964c8285a37b71fe838a44c05c4 Mon Sep 17 00:00:00 2001
From: Joerg Roedel <jroedel@suse.de>
Date: Wed, 4 Feb 2015 15:50:38 +0100
Subject: [PATCH 1/2] iommu/amd: Use wait_event in put_pasid_state_wait

Now that I learned about possible spurious wakeups this
place needs fixing too. Replace the self-coded sleep variant
with the generic wait_event() helper.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
drivers/iommu/amd_iommu_v2.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/amd_iommu_v2.c b/drivers/iommu/amd_iommu_v2.c
index b6398d7..e01bc8f 100644
--- a/drivers/iommu/amd_iommu_v2.c
+++ b/drivers/iommu/amd_iommu_v2.c
@@ -266,14 +266,13 @@ static void put_pasid_state(struct pasid_state *pasid_state)

static void put_pasid_state_wait(struct pasid_state *pasid_state)
{
- DEFINE_WAIT(wait);
+ /* Drop our reference */
+ atomic_dec(&pasid_state->count);

- prepare_to_wait(&pasid_state->wq, &wait, TASK_UNINTERRUPTIBLE);
+ /* Wait for others to drop their references */
+ wait_event(pasid_state->wq, !atomic_read(&pasid_state->count));

- if (!atomic_dec_and_test(&pasid_state->count))
- schedule();
-
- finish_wait(&pasid_state->wq, &wait);
+ /* Get rid of it */
free_pasid_state(pasid_state);
}

--
1.8.4.5


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