Re: [PATCH tip/core/rcu 23/41] sched: Replace synchronize_sched() with synchronize_rcu()

Peter Zijlstra
2018-11-12T00:12:57Z

On Sun, Nov 11, 2018 at 11:43:52AM -0800, Paul E. McKenney wrote:
> Now that synchronize_rcu() waits for preempt-disable regions of code
> as well as RCU read-side critical sections, synchronize_sched() can be
> replaced by synchronize_rcu(). This commit therefore makes this change.

Yes, but it also waits for an actual RCU quiestent state, which makes
synchoinize_rcu() potentially much more expensive than an actual
synchronize_sched().

So why are we doing this?