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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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