On Mon, May 25, 2020 at 08:10:27AM -0600, Jens Axboe wrote: > I think the odd part here is that task_tick_numa() checks for a > valid mm, and queues work if the task has it. But for the sqpoll > kthread, the mm can come and go. By the time the task work is run, > the mm is gone and we oops on current->mm == NULL. > > I think the below should fix it: > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 538ba5d94e99..24a8557f001f 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -2908,7 +2908,8 @@ static void task_tick_numa(struct rq *rq, struct task_struct *curr) > /* > * We don't care about NUMA placement if we don't have memory. > */ > - if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work) > + if (!curr->mm || (curr->flags & (PF_EXITING | PF_KTHREAD)) || > + work->next != work) > return; Ah, I think that's one more instance of '!p->mm' != is_kthread(). A while ago someone went and cleaned a bunch of them up. Clearly this one was missed. I'm thinking just: if ((curr->flags & (PF_EXITING | PF_KTHREAD)) || work->next != work) should be enough.
