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.
