Am 12.05.20 um 10:59 schrieb Daniel Vetter:
But only for non-zero timeout, to avoid false positives.

One question here is whether the might_sleep should be unconditional,
or only for real timeouts. I'm not sure, so went with the more
defensive option. But in the interest of locking down the cross-driver
dma_fence rules we might want to be more aggressive.

Cc: linux-me...@vger.kernel.org
Cc: linaro-mm-...@lists.linaro.org
Cc: linux-r...@vger.kernel.org
Cc: amd-...@lists.freedesktop.org
Cc: intel-...@lists.freedesktop.org
Cc: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankho...@linux.intel.com>
Cc: Christian König <christian.koe...@amd.com>
Signed-off-by: Daniel Vetter <daniel.vet...@intel.com>
---
  drivers/dma-buf/dma-fence.c | 3 +++
  1 file changed, 3 insertions(+)

diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 052a41e2451c..6802125349fb 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -208,6 +208,9 @@ dma_fence_wait_timeout(struct dma_fence *fence, bool intr, 
signed long timeout)
        if (WARN_ON(timeout < 0))
                return -EINVAL;
+ if (timeout > 0)
+               might_sleep();
+

I would rather like to see might_sleep() called here all the time even with timeout==0.

IIRC I removed the code in TTM abusing this in atomic context quite a while ago, but could be that some leaked in again or it is called in atomic context elsewhere as well.

Christian.

        trace_dma_fence_wait_start(fence);
        if (fence->ops->wait)
                ret = fence->ops->wait(fence, intr, timeout);

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