On Wed 07-11-18 18:45:27, Tetsuo Handa wrote: > On 2018/11/06 21:42, Michal Hocko wrote: > > On Tue 06-11-18 18:44:43, Tetsuo Handa wrote: > > [...] > >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c > >> index 6e1469b..a97648a 100644 > >> --- a/mm/memcontrol.c > >> +++ b/mm/memcontrol.c > >> @@ -1382,8 +1382,13 @@ static bool mem_cgroup_out_of_memory(struct > >> mem_cgroup *memcg, gfp_t gfp_mask, > >> }; > >> bool ret; > >> > >> - mutex_lock(&oom_lock); > >> - ret = out_of_memory(&oc); > >> + if (mutex_lock_killable(&oom_lock)) > >> + return true; > >> + /* > >> + * A few threads which were not waiting at mutex_lock_killable() can > >> + * fail to bail out. Therefore, check again after holding oom_lock. > >> + */ > >> + ret = fatal_signal_pending(current) || out_of_memory(&oc); > >> mutex_unlock(&oom_lock); > >> return ret; > >> } > > > > If we are goging with a memcg specific thingy then I really prefer > > tsk_is_oom_victim approach. Or is there any reason why this is not > > suitable? > > > > Why need to wait for mark_oom_victim() called after slow printk() messages? > > If current thread got Ctrl-C and thus current thread can terminate, what is > nice with waiting for the OOM killer? If there are several OOM events in > multiple memcg domains waiting for completion of printk() messages? I don't > see points with waiting for oom_lock, for try_charge() already allows current > thread to terminate due to fatal_signal_pending() test.
mutex_lock_killable would take care of exiting task already. I would then still prefer to check for mark_oom_victim because that is not racy with the exit path clearing signals. I can update my patch to use _killable lock variant if we are really going with the memcg specific fix. Johaness? -- Michal Hocko SUSE Labs
