On Mon 30-07-18 23:34:23, Tetsuo Handa wrote: > On 2018/07/30 18:32, Michal Hocko wrote: [...] > > This one is waiting for draining and we are in mm_percpu_wq WQ context > > which has its rescuer so no other activity can block us for ever. So > > this certainly shouldn't deadlock. It can be dead slow but well, this is > > what you will get when your shoot your system to death. > > We need schedule_timeout_*() to allow such WQ_MEM_RECLAIM workqueues to wake up. (Tejun, > is my understanding correct?) Lack of schedule_timeout_*() does block WQ_MEM_RECLAIM > workqueues forever. Hmm. This doesn't match my understanding of what WQ_MEM_RECLAIM actually guarantees. If you are right then the whole thing sounds quite fragile to me TBH. Anyway we would at least have an explanation for what you are seeing. -- Michal Hocko SUSE Labs
