Re: [PATCH 05/71] drm/i915/execlists: Disable submission tasklets when rescheduling

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Quoting Tvrtko Ursulin (2018-05-04 10:15:20)
> On 03/05/2018 20:50, Chris Wilson wrote:
> The second hunk is a bit more difficult. It creates a longer softirq-off 
> section, which is a slight negative, and I am unsure how much it 
> actually closes the race with tasklets in practice. So it may be the 
> only benefit is to reduce fiddles of both preempt count and 
> local_bh_disable, to fiddle just one.

Remember that local_bh_disable() is just a fiddle with preempt-count and
that the local tasklet doesn't run during the !preemptible section
anyway. So it does remove one preemption point (in clearing the
preempt-count) but that is of dubious merit since we would then need to
kick the submission tasklet again immediately (from the preempt-count
pov) afterwards.
-Chris
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