| Date | Mon, 16 Jan 2017 18:11:30 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH tip/core/rcu 11/20] sched,rcu: Make cond_resched() provide RCU quiescent state |
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On Sat, Jan 14, 2017 at 01:13:12AM -0800, Paul E. McKenney wrote: > There is some confusion as to which of cond_resched() or > cond_resched_rcu_qs() should be added to long in-kernel loops. > This commit therefore eliminates the decision by adding RCU > quiescent states to cond_resched().
Which would make: rcu_read_lock(); cond_resched(); rcu_read_unlock(); invalid under preemptible RCU. Is it already?
> Warning: This is a prototype. For example, it does not correctly > handle Tasks RCU. Which is OK for the moment, given that no one > actually uses Tasks RCU yet.
> --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -4907,6 +4907,7 @@ int __sched _cond_resched(void) > preempt_schedule_common(); > return 1; > } > + rcu_all_qs(); > return 0; > }
Still not a real fan of this, it does make cond_resched() touch a bunch more cachelines, also, I suppose that if we're going to do this, we should make __cond_resched_lock() and __cond_resched_softirq() act similarly.
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