Re: INFO: rcu detected stall in shmem_fault
- Date: Tue, 9 Oct 2018 21:11:48 -0700 (PDT)
- From: David Rientjes <rientjes@xxxxxxxxxx>
- Subject: Re: 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.
> 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
- 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.