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To do so, it replaced the automatically locking > dma_fence_is_signaled() with manual locks plus > dma_fence_is_signaled_locked(). > > For someone browsing through the code, this reads very much like a > cleanup or rework leftover. Future contributors and / or new maintainers > not familiar with the history might be tempted to remove that bugfix. > > Document the bugfix. > > Signed-off-by: Philipp Stanner Reviewed-by: Christian König > --- > (I did not test this) > --- > drivers/gpu/drm/nouveau/nouveau_drm.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c > index 42a81166f3a9..519a0c164a72 100644 > --- a/drivers/gpu/drm/nouveau/nouveau_drm.c > +++ b/drivers/gpu/drm/nouveau/nouveau_drm.c > @@ -159,6 +159,13 @@ nouveau_cli_work_ready(struct dma_fence *fence) > unsigned long flags; > bool ret = true; > > + /* > + * This is not a cleanup / rework leftover, but a bugfix to prevent a > + * race with someone signalling the fence. The locked > + * dma_fence_is_signaled() cannot be used. The dma_fence implementation > + * is not fully synchronized with locks, but also uses atomic bits, > + * which can cause the dma_fence_put() below to be executed too soon. > + */ > dma_fence_lock_irqsave(fence, flags); > if (!dma_fence_is_signaled_locked(fence)) > ret = false;