lkml.org 
[lkml]   [2018]   [Oct]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: INFO: rcu detected stall in shmem_fault
On Wed, 10 Oct 2018, Tetsuo Handa wrote:

> syzbot is hitting RCU stall due to memcg-OOM event.
> https://syzkaller.appspot.com/bug?id=4ae3fff7fcf4c33a47c1192d2d62d2e03efffa64
>
> What should we do if memcg-OOM found no killable task because the allocating task
> was oom_score_adj == -1000 ? Flooding printk() until RCU stall watchdog fires
> (which seems to be caused by commit 3100dab2aa09dc6e ("mm: memcontrol: print proper
> OOM header when no eligible victim left") because syzbot was terminating the test
> upon WARN(1) removed by that commit) is not a good behavior.
>

Not printing anything would be the obvious solution but the ideal solution
would probably involve

- adding feedback to the memcg oom killer that there are no killable
processes,

- adding complete coverage for memcg_oom_recover() in all uncharge paths
where the oom memcg's page_counter is decremented, and

- having all processes stall until memcg_oom_recover() is called so
looping back into try_charge() has a reasonable expectation to succeed.

\
 
 \ /
  Last update: 2018-10-10 06:13    [W:0.070 / U:0.420 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site