Michal Hocko wrote:
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -898,6 +898,7 @@ static void __oom_kill_process(struct task_struct *victim)
>               if (unlikely(p->flags & PF_KTHREAD))
>                       continue;
>               do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, PIDTYPE_TGID);
> +             mark_oom_victim(p);
>       }
>       rcu_read_unlock();
>  
> -- 

Wrong. Either

---
 mm/oom_kill.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index f10aa53..99b36ff 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -879,6 +879,8 @@ static void __oom_kill_process(struct task_struct *victim)
         */
        rcu_read_lock();
        for_each_process(p) {
+               struct task_struct *t;
+
                if (!process_shares_mm(p, mm))
                        continue;
                if (same_thread_group(p, victim))
@@ -898,6 +900,11 @@ static void __oom_kill_process(struct task_struct *victim)
                if (unlikely(p->flags & PF_KTHREAD))
                        continue;
                do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, PIDTYPE_TGID);
+               t = find_lock_task_mm(p);
+               if (!t)
+                       continue;
+               mark_oom_victim(t);
+               task_unlock(t);
        }
        rcu_read_unlock();
 
-- 
1.8.3.1

or

---
 mm/oom_kill.c | 32 +++++++++++++++++++-------------
 1 file changed, 19 insertions(+), 13 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index f10aa53..7fa9b7c 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -854,13 +854,6 @@ static void __oom_kill_process(struct task_struct *victim)
        count_vm_event(OOM_KILL);
        memcg_memory_event_mm(mm, MEMCG_OOM_KILL);
 
-       /*
-        * We should send SIGKILL before granting access to memory reserves
-        * in order to prevent the OOM victim from depleting the memory
-        * reserves from the user space under its control.
-        */
-       do_send_sig_info(SIGKILL, SEND_SIG_FORCED, victim, PIDTYPE_TGID);
-       mark_oom_victim(victim);
        pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, 
file-rss:%lukB, shmem-rss:%lukB\n",
                task_pid_nr(victim), victim->comm, K(victim->mm->total_vm),
                K(get_mm_counter(victim->mm, MM_ANONPAGES)),
@@ -879,11 +872,23 @@ static void __oom_kill_process(struct task_struct *victim)
         */
        rcu_read_lock();
        for_each_process(p) {
-               if (!process_shares_mm(p, mm))
+               struct task_struct *t;
+
+               /*
+                * No use_mm() user needs to read from the userspace so we are
+                * ok to reap it.
+                */
+               if (unlikely(p->flags & PF_KTHREAD))
+                       continue;
+               t = find_lock_task_mm(p);
+               if (!t)
                        continue;
-               if (same_thread_group(p, victim))
+               if (likely(t->mm != mm)) {
+                       task_unlock(t);
                        continue;
+               }
                if (is_global_init(p)) {
+                       task_unlock(t);
                        can_oom_reap = false;
                        set_bit(MMF_OOM_SKIP, &mm->flags);
                        pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
@@ -892,12 +897,13 @@ static void __oom_kill_process(struct task_struct *victim)
                        continue;
                }
                /*
-                * No use_mm() user needs to read from the userspace so we are
-                * ok to reap it.
+                * We should send SIGKILL before granting access to memory
+                * reserves in order to prevent the OOM victim from depleting
+                * the memory reserves from the user space under its control.
                 */
-               if (unlikely(p->flags & PF_KTHREAD))
-                       continue;
                do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, PIDTYPE_TGID);
+               mark_oom_victim(t);
+               task_unlock(t);
        }
        rcu_read_unlock();
 
-- 
1.8.3.1

will be needed.

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