On Fri, Jun 30, 2017 at 03:50:33PM -0400, Alan Stern wrote: > On Fri, 30 Jun 2017, Oleg Nesterov wrote: > > > On 06/30, Paul E. McKenney wrote: > > > > > > On Fri, Jun 30, 2017 at 05:20:10PM +0200, Oleg Nesterov wrote: > > > > > > > > I do not think the overhead will be noticeable in this particular case. > > > > > > > > But I am not sure I understand why do we want to unlock_wait. Yes I agree, > > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > > > if it was not clear, I tried to say "why do we want to _remove_ unlock_wait". > > > > > > it has some problems, but still... > > > > > > > > The code above looks strange for me. If we are going to repeat this pattern > > > > the perhaps we should add a helper for lock+unlock and name it unlock_wait2 ;) > > > > > > > > If not, we should probably change this code more: > > > > > > This looks -much- better than my patch! May I have your Signed-off-by? > > > > Only if you promise to replace all RCU flavors with a single simple implementation > > based on rwlock ;) > > > > Seriously, of course I won't argue, and it seems that nobody except me likes > > this primitive, but to me spin_unlock_wait() looks like synchronize_rcu(() and > > sometimes it makes sense. > > If it looks like synchronize_rcu(), why not actually use > synchronize_rcu()? My guess is that the latencies of synchronize_rcu() don't suit his needs. When the lock is not held, spin_unlock_wait() is quite fast, even compared to expedited grace periods. Thanx, Paul > Alan Stern > > > Including this particular case. task_work_run() is going to flush/destroy the > > ->task_works list, so it needs to wait until all currently executing "readers" > > (task_work_cancel()'s which have started before ->task_works was updated) have > > completed. > -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
