Messages in this thread | | | Date | Wed, 30 Nov 2016 12:09:44 +0100 | From | Michal Hocko <> | Subject | Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and `mem_cgroup_shrink_node` |
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[CCing Paul]
On Wed 30-11-16 11:28:34, Donald Buczek wrote: [...] > shrink_active_list gets and releases the spinlock and calls cond_resched(). > This should give other tasks a chance to run. Just as an experiment, I'm > trying > > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -1921,7 +1921,7 @@ static void shrink_active_list(unsigned long > nr_to_scan, > spin_unlock_irq(&pgdat->lru_lock); > > while (!list_empty(&l_hold)) { > - cond_resched(); > + cond_resched_rcu_qs(); > page = lru_to_page(&l_hold); > list_del(&page->lru); > > and didn't hit a rcu_sched warning for >21 hours uptime now. We'll see.
This is really interesting! Is it possible that the RCU stall detector is somehow confused?
> Is preemption disabled for another reason?
I do not think so. I will have to double check the code but this is a standard sleepable context. Just wondering what is the PREEMPT configuration here? -- Michal Hocko SUSE Labs
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