Messages in this thread | | | Date | Mon, 09 Jan 2006 23:31:20 +0300 | From | Oleg Nesterov <> | Subject | Re: [PATCH 2/5] rcu: don't check ->donelist in __rcu_pending() |
| |
"Paul E. McKenney" wrote: > > On Sun, Jan 08, 2006 at 10:19:24PM +0300, Oleg Nesterov wrote: > > ->donelist becomes != NULL only in rcu_process_callbacks(). > > > > rcu_process_callbacks() always calls rcu_do_batch() when > > ->donelist != NULL. > > > > rcu_do_batch() schedules rcu_process_callbacks() again if > > ->donelist was not flushed entirely. > > > > So ->donelist != NULL means that rcu_tasklet is either > > TASKLET_STATE_SCHED or TASKLET_STATE_RUN, we don't need to > > check it in __rcu_pending(). > > As Vatsa noted, this is needed if the CPU-hotplug case moves > from ->donelist to ->donelist. It could be omitted if CPU-hotplug > instead moves from ->donelist to ->nextlist, as is the case in Oleg's > patch. The extra grace-period delay should not be a problem for the > presumably rare hotplug case, but:
Just to be sure. So do you agree that CPU-hotplug is buggy now (without that patch) ?
> o the extra test in __rcu_pending() should be quite inexpensive, > since the cacheline is already loaded given the earlier tests.
Yes, it was a cleanup, not an optimization.
> o although tasklet_schedule() looks to be perfectly reliable > right now, and although any bugs in tasklet_schedule() must > be fixed, having RCU leakage be the major symptom of > tasklet_schedule() failure sounds quite unfriendly to me. > > So I am not (yet) convinced that this patch is the way to go.
Ok, I agree.
Oleg. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |