Re: [PATCH v2 2/4] dma-buf: enable signaling for the stub fence on debug

[Yadav, Arvind]

On 9/6/2022 12:39 PM, Christian König wrote:
> Am 05.09.22 um 18:35 schrieb Arvind Yadav:
> > Here's on debug enabling software signaling for the stub fence
> > which is always signaled. This fence should enable software
> > signaling otherwise the AMD GPU scheduler will cause a GPU reset
> > due to a GPU scheduler cleanup activity timeout.
> >
> > Signed-off-by: Arvind Yadav <Arvind.Yadav@xxxxxxx>
> > ---
> >
> > Changes in v1 :
> > 1- Addressing Christian's comment to remove unnecessary callback.
> > 2- Replacing CONFIG_DEBUG_WW_MUTEX_SLOWPATH instead of CONFIG_DEBUG_FS.
> > 3- The version of this patch is also changed and previously
> > it was [PATCH 3/4]
> >
> > ---
> >   drivers/dma-buf/dma-fence.c | 7 +++++++
> >   1 file changed, 7 insertions(+)
> >
> > diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> > index 066400ed8841..2378b12538c4 100644
> > --- a/drivers/dma-buf/dma-fence.c
> > +++ b/drivers/dma-buf/dma-fence.c
> > @@ -27,6 +27,10 @@ EXPORT_TRACEPOINT_SYMBOL(dma_fence_signaled);
> >   static DEFINE_SPINLOCK(dma_fence_stub_lock);
> >   static struct dma_fence dma_fence_stub;
> >   +#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
> > +static bool __dma_fence_enable_signaling(struct dma_fence *fence);
> > +#endif
> > +
>
> I would rename the function to something like 
> dma_fence_enable_signaling_locked().
>
> And please don't add any #ifdef if it isn't absolutely necessary. This 
> makes the code pretty fragile.
>
> >   /*
> >    * fence context counter: each execution context should have its own
> >    * fence context, this allows checking if fences belong to the same
> > @@ -136,6 +140,9 @@ struct dma_fence *dma_fence_get_stub(void)
> >                      &dma_fence_stub_ops,
> >                      &dma_fence_stub_lock,
> >                      0, 0);
> > +#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
> > +        __dma_fence_enable_signaling(&dma_fence_stub);
> > +#endif
>
> Alternatively in this particular case you could just set the bit 
> manually here since this is part of the dma_fence code anyway.
>
> Christian.
As per per review comment. I will set the bit manually.

~arvind

> > dma_fence_signal_locked(&dma_fence_stub);
> >       }
> >       spin_unlock(&dma_fence_stub_lock);