[PATCH] dma-buf/fence: Avoid use of uninitialised timestamp

[Chris Wilson]

On Tue, Feb 14, 2017 at 11:40:38AM -0200, Gustavo Padovan wrote:
> Hi Chris,
> 
> 2017-02-14 Chris Wilson <chris at chris-wilson.co.uk>:
> > diff --git a/drivers/dma-buf/sync_debug.c b/drivers/dma-buf/sync_debug.c
> > index c769dc653b34..bfead12390f2 100644
> > --- a/drivers/dma-buf/sync_debug.c
> > +++ b/drivers/dma-buf/sync_debug.c
> > @@ -84,7 +84,7 @@ static void sync_print_fence(struct seq_file *s,
> >  		   show ? "_" : "",
> >  		   sync_status_str(status));
> >  
> > -	if (status) {
> > +	if (test_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags)) {
> >  		struct timespec64 ts64 =
> >  			ktime_to_timespec64(fence->timestamp);
> 
> How about add this test_bit() to dma_fence_is_signaled_locked() so
> we test both for DMA_FENCE_FLAG_SIGNALED_BIT and
> DMA_FENCE_FLAG_TIMESTAMP_BIT there at the same time?

I was thinking of only using it as communication with the timestamp
user. That avoids getting into the situation as to which bit truly means
is-signaled and we still only synchronize on SIGNALED_BIT.

It would be possible, but I don't think it makes anything simpler.

One thing that occurs to me is whether we should be setting the
timestamp when we set an error. The above (sync_debug though) implies
that it expects the error to have the timestamp. sync_fence_info could
go either way.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre