[Intel-gfx] [PATCH v2 1/3] drm/i915: Enable lockless lookup of request tracking via RCU

[Peter Zijlstra]

On Tue, Jan 05, 2016 at 04:02:13PM +0100, Peter Zijlstra wrote:
> > Shouldn't the slab subsystem do this for us if we request it delays the
> > actual kfree? Seems like a core bug to me ... Adding more folks.
> 
> note that sync_rcu() can take a terribly long time.. but yes, I seem to
> remember Paul talking about adding this to reclaim paths for just this
> reason. Not sure that ever happened thouhg.

Also, you might be wanting rcu_barrier() instead, that not only waits
for a GP to complete, but also for all pending callbacks to be
processed.

Without the latter there might still not be anything to free after it.