On Wed, 17 Jul 2019 19:55:01 +0900 Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote:
> Currently dump_tasks() might call printk() for many thousands times under
> RCU, which might take many minutes for slow consoles. Therefore, split
> dump_tasks() into three stages; take a snapshot of possible OOM victim
> candidates under RCU, dump the snapshot from reschedulable context, and
> destroy the snapshot.
>
> In a future patch, the first stage would be moved to select_bad_process()
> and the third stage would be moved to after oom_kill_process(), and will
> simplify refcount handling.
Look straightforward enough.
>
> ...
>
> static void dump_tasks(struct oom_control *oc)
> {
> - pr_info("Tasks state (memory values in pages):\n");
> - pr_info("[ pid ] uid tgid total_vm rss pgtables_bytes swapents oom_score_adj name\n");
> + static LIST_HEAD(list);
I don't think this needs to be static?
> + struct task_struct *p;
> + struct task_struct *t;
>
> if (is_memcg_oom(oc))
> - mem_cgroup_scan_tasks(oc->memcg, dump_task, oc);
> + mem_cgroup_scan_tasks(oc->memcg, add_candidate_task, &list);
> else {
> - struct task_struct *p;
> -
> rcu_read_lock();
> for_each_process(p)
> - dump_task(p, oc);
> + add_candidate_task(p, &list);
> rcu_read_unlock();
> }
> + pr_info("Tasks state (memory values in pages):\n");
> + pr_info("[ pid ] uid tgid total_vm rss pgtables_bytes swapents oom_score_adj name\n");
> + list_for_each_entry(p, &list, oom_victim_list) {
> + cond_resched();
> + /* p may not have freeable memory in nodemask */
> + if (!is_memcg_oom(oc) && !oom_cpuset_eligible(p, oc))
> + continue;
> + /* All of p's threads might have already detached their mm's. */
> + t = find_lock_task_mm(p);
> + if (!t)
> + continue;
> + pr_info("[%7d] %5d %5d %8lu %8lu %8ld %8lu %5hd %s\n",
> + t->pid, from_kuid(&init_user_ns, task_uid(t)),
> + t->tgid, t->mm->total_vm, get_mm_rss(t->mm),
> + mm_pgtables_bytes(t->mm),
> + get_mm_counter(t->mm, MM_SWAPENTS),
> + t->signal->oom_score_adj, t->comm);
> + task_unlock(t);
> + }
> + list_for_each_entry_safe(p, t, &list, oom_victim_list) {
> + list_del(&p->oom_victim_list);
> + put_task_struct(p);
> + }
> }
