On Wed 22-06-16 06:47:48, Tetsuo Handa wrote: > Michal Hocko wrote: > > On Wed 22-06-16 00:32:29, Tetsuo Handa wrote: > > > Michal Hocko wrote: > > [...] > > > > Hmm, what about the following instead. It is rather a workaround than a > > > > full flaged fix but it seems much more easier and shouldn't introduce > > > > new issues. > > > > > > Yes, I think that will work. But I think below patch (marking > > > signal_struct > > > to ignore TIF_MEMDIE instead of clearing TIF_MEMDIE from task_struct) on > > > top of > > > current linux.git will implement no-lockup requirement. No race is > > > possible unlike > > > "[PATCH 10/10] mm, oom: hide mm which is shared with kthread or global > > > init". > > > > Not really. Because without the exit_oom_victim from oom_reaper you have > > no guarantee that the oom_killer_disable will ever return. I have > > mentioned that in the changelog. There is simply no guarantee the oom > > victim will ever reach exit_mm->exit_oom_victim. > > Why? Since any allocation after setting oom_killer_disabled = true will be > forced to fail, nobody will be blocked on waiting for memory allocation. Thus, > the TIF_MEMDIE tasks will eventually reach exit_mm->exit_oom_victim, won't it?
What if it gets blocked waiting for an operation which cannot make any forward progress because it cannot proceed with an allocation (e.g. an open coded allocation retry loop - not that uncommon when sending a bio)? I mean if we want to guarantee a forward progress then there has to be something to clear the flag no matter in what state the oom victim is or give up on oom_killer_disable. -- Michal Hocko SUSE Labs
