[Intel-gfx] [PATCH] drm/i915: Convert breadcrumbs spinlock to be irqsafe

[Chris Wilson]

On Fri, Oct 28, 2016 at 11:27:43AM +0100, Tvrtko Ursulin wrote:
> 
> 
> On 28/10/16 11:10, Chris Wilson wrote:
> >On Fri, Oct 28, 2016 at 10:42:22AM +0100, Tvrtko Ursulin wrote:
> >>
> >>
> >>On 27/10/16 17:10, Chris Wilson wrote:
> >>>The breadcrumbs are about to be used from within IRQ context sections,
> >>>therefore we need to employ the irqsafe spinlock variants.
> >>>
> >>>(This is split out of the defer global seqno allocation patch due to
> >>>realisation that we need a more complete conversion if we want to defer
> >>>request submission even further.)
> >
> >[snip]
> >
> >>Assuming I got the above right and you agree to change it:
> >
> >You made me go and reduce them to _bh as appropriate anyway!!!
> 
> Hm, but can't enable signalling be called with irqs disabled when
> fences are exported?

Yes, but that supercedes the spin_lock_bh, so we can just call
spin_lock() in enabling_signaling as we can assert that we will always
be called with irqs disabled here (due to spin_lock_irqsafe(fence->lock)
in the callpath).
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre