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    Subject[PATCH 4.4 046/131] android: unconditionally remove callbacks in sync_fence_free()
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    [ Upstream commit 699f685569434510d944e419f4048c4e3ba8d631 ]

    Using fence->status to determine whether or not there are callbacks
    remaining on the sync_fence is racy since fence->status may have been
    decremented to 0 on another CPU before fence_check_cb_func() has
    completed. By unconditionally calling fence_remove_callback() for each
    fence in the sync_fence, we guarantee that each callback has either
    completed (since fence_remove_callback() grabs the fence lock) or been
    removed.

    Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
    Signed-off-by: Dmitry Torokhov <dtor@chromium.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/staging/android/sync.c | 6 ++----
    1 file changed, 2 insertions(+), 4 deletions(-)

    diff --git a/drivers/staging/android/sync.c b/drivers/staging/android/sync.c
    index f83e00c78051..50a9945da27e 100644
    --- a/drivers/staging/android/sync.c
    +++ b/drivers/staging/android/sync.c
    @@ -519,12 +519,10 @@ static const struct fence_ops android_fence_ops = {
    static void sync_fence_free(struct kref *kref)
    {
    struct sync_fence *fence = container_of(kref, struct sync_fence, kref);
    - int i, status = atomic_read(&fence->status);
    + int i;

    for (i = 0; i < fence->num_fences; ++i) {
    - if (status)
    - fence_remove_callback(fence->cbs[i].sync_pt,
    - &fence->cbs[i].cb);
    + fence_remove_callback(fence->cbs[i].sync_pt, &fence->cbs[i].cb);
    fence_put(fence->cbs[i].sync_pt);
    }

    --
    2.19.1


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