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@xxxxxxxxxxxxx
Tel: +49 30 8413 1433
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