On Sun, 21 Feb 2016, Tetsuo Handa wrote:
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index ae8b81c..390ec2c 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1253,16 +1253,6 @@ static void mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
>
> mutex_lock(&oom_lock);
>
> - /*
> - * If current has a pending SIGKILL or is exiting, then automatically
> - * select it. The goal is to allow it to allocate so that it may
> - * quickly exit and free its memory.
> - */
> - if (fatal_signal_pending(current) || task_will_free_mem(current)) {
> - mark_oom_victim(current);
> - goto unlock;
> - }
> -
> check_panic_on_oom(&oc, CONSTRAINT_MEMCG, memcg);
> totalpages = mem_cgroup_get_limit(memcg) ? : 1;
> for_each_mem_cgroup_tree(iter, memcg) {
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index d7bb9c1..5e8563a 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -684,19 +684,6 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p,
> DEFAULT_RATELIMIT_BURST);
> bool can_oom_reap = true;
>
> - /*
> - * If the task is already exiting, don't alarm the sysadmin or kill
> - * its children or threads, just set TIF_MEMDIE so it can die quickly
> - */
> - task_lock(p);
> - if (p->mm && task_will_free_mem(p)) {
> - mark_oom_victim(p);
> - task_unlock(p);
> - put_task_struct(p);
> - return;
> - }
> - task_unlock(p);
> -
> if (__ratelimit(&oom_rs))
> dump_header(oc, p, memcg);
>
> @@ -759,20 +746,15 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p,
> task_unlock(victim);
>
> /*
> - * Kill all user processes sharing victim->mm in other thread groups, if
> - * any. They don't get access to memory reserves, though, to avoid
> - * depletion of all memory. This prevents mm->mmap_sem livelock when an
> - * oom killed thread cannot exit because it requires the semaphore and
> - * its contended by another thread trying to allocate memory itself.
> - * That thread will now get access to memory reserves since it has a
> - * pending fatal signal.
> + * Kill all user processes sharing victim->mm. This reduces possibility
> + * of hitting mm->mmap_sem livelock when an oom killed thread cannot
> + * exit because it requires the semaphore and its contended by another
> + * thread trying to allocate memory itself.
> */
> rcu_read_lock();
> for_each_process(p) {
> if (!process_shares_mm(p, mm))
> continue;
> - if (same_thread_group(p, victim))
> - continue;
> if (unlikely(p->flags & PF_KTHREAD) || is_global_init(p) ||
> p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) {
> /*
> @@ -784,6 +766,12 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p,
> continue;
> }
> do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);
> + for_each_thread(p, t) {
> + task_lock(t);
> + if (t->mm)
> + mark_oom_victim(t);
> + task_unlock(t);
> + }
> }
> rcu_read_unlock();
>
> @@ -860,20 +848,6 @@ bool out_of_memory(struct oom_control *oc)
> return true;
>
> /*
> - * If current has a pending SIGKILL or is exiting, then automatically
> - * select it. The goal is to allow it to allocate so that it may
> - * quickly exit and free its memory.
> - *
> - * But don't select if current has already released its mm and cleared
> - * TIF_MEMDIE flag at exit_mm(), otherwise an OOM livelock may occur.
> - */
> - if (current->mm &&
> - (fatal_signal_pending(current) || task_will_free_mem(current))) {
> - mark_oom_victim(current);
> - return true;
> - }
> -
> - /*
> * Check if there were limitations on the allocation (only relevant for
> * NUMA) that may require different handling.
> */
No, NACK. You cannot prohibit an exiting process from gaining access to
memory reserves and randomly killing another process without additional
chances of a livelock. The goal is for an exiting or killed process to
be able to exit so it can free its memory, not kill additional processes.
Please start trimming your cc list, I seriously doubt all these people are
interested in this thread.
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