[Nouveau] [PATCH] drm/nouveau: reduce usage of fence spinlock to when absolutely necessary

[Stephane Marchesin]

The update of last_sequence_irq is still racy with this patch...

So let me explain:
- non-interrupt context starts reading last_sequence_irq
- irq happens in the middle (because it is not an atomic read, it's
possible, albeit it doesn't happen on x86 so just saying "it works on my
x86" isn't enough)
- last_sequence_irq is modified in interrupt context
- second half of last_sequence_irq happens in normal context and results in
a bogus value

Stephane
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