Quoting Gustavo Padovan (2018-01-31 12:32:21)
> Hi,
>
> 2017-08-11 Jason Ekstrand <jason@xxxxxxxxxxxxxx>:
>
> > From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> >
> > This is an illegal scenario, to free the fence whilst there are pending
> > callbacks. Currently, we emit a WARN and then cast aside the callbacks
> > leaving them dangling. Alternatively, we could set an error on the fence
> > and then signal fence so that any dependency chains from the fence can
> > be tidied up, and if they care they can check for the error.
> >
> > The question is whether or not the cure is worse than the disease
> > (premature fence signaling is never pretty).
> >
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > ---
> > drivers/dma-buf/dma-fence.c | 14 +++++++++++++-
> > 1 file changed, 13 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> > index 0cac367..4062708 100644
> > --- a/drivers/dma-buf/dma-fence.c
> > +++ b/drivers/dma-buf/dma-fence.c
> > @@ -172,7 +172,19 @@ void dma_fence_release(struct kref *kref)
> >
> > trace_dma_fence_destroy(fence);
> >
> > - WARN_ON(!list_empty(&fence->cb_list));
> > + if (WARN_ON(!list_empty(&fence->cb_list))) {
> > + unsigned long flags;
> > +
> > + /*
> > + * This should never happen, but if it does make sure that we
> > + * don't leave chains dangling. We set the error flag first
> > + * so that the callbacks know this signal is due to an error.
> > + */
> > + spin_lock_irqsave(fence->lock, flags);
> > + fence->error = -EDEADLK;
> > + dma_fence_signal_locked(fence);
> > + spin_unlock_irqrestore(fence->lock, flags);
> > + }
>
> Thanks for the patch!
>
> Reviewed-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>
If you are picking up this version, please also include
a Reviewed-by: Christian König <christian.koenig@xxxxxxx> given to an
earlier posting, which included a discussion on the pitiful lack of
EHUMAN.
-Chris
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