Messages in this thread | | | Subject | Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and `mem_cgroup_shrink_node` | From | Donald Buczek <> | Date | Wed, 30 Nov 2016 12:43:44 +0100 |
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On 11/30/16 12:09, Michal Hocko wrote: > [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?
Wait... 21 hours is not yet a test result.
>> 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?
buczek@null:~$ zcat /proc/config.gz |grep PREE CONFIG_PREEMPT_NOTIFIERS=y # CONFIG_PREEMPT_NONE is not set CONFIG_PREEMPT_VOLUNTARY=y # CONFIG_PREEMPT is not set
Thanks Donald
-- Donald Buczek buczek@molgen.mpg.de Tel: +49 30 8413 1433
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