mm, oom: hide mm which is shared with kthread or global init

[cascardo/linux.git] / mm / oom_kill.c

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index bfddc93..4c21f74 100644 (file)
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -283,10 +283,22 @@ enum oom_scan_t oom_scan_process_thread(struct oom_control *oc,
 
        /*
         * This task already has access to memory reserves and is being killed.
-        * Don't allow any other task to have access to the reserves.
+        * Don't allow any other task to have access to the reserves unless
+        * the task has MMF_OOM_REAPED because chances that it would release
+        * any memory is quite low.
         */
-       if (!is_sysrq_oom(oc) && atomic_read(&task->signal->oom_victims))
-               return OOM_SCAN_ABORT;
+       if (!is_sysrq_oom(oc) && atomic_read(&task->signal->oom_victims)) {
+               struct task_struct *p = find_lock_task_mm(task);
+               enum oom_scan_t ret = OOM_SCAN_ABORT;
+
+               if (p) {
+                       if (test_bit(MMF_OOM_REAPED, &p->mm->flags))
+                               ret = OOM_SCAN_CONTINUE;
+                       task_unlock(p);
+               }
+
+               return ret;
+       }
 
        /*
         * If task is allocating a lot of memory and has been marked to be
@@ -913,9 +925,14 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p,
                        /*
                         * We cannot use oom_reaper for the mm shared by this
                         * process because it wouldn't get killed and so the
-                        * memory might be still used.
+                        * memory might be still used. Hide the mm from the oom
+                        * killer to guarantee OOM forward progress.
                         */
                        can_oom_reap = false;
+                       set_bit(MMF_OOM_REAPED, &mm->flags);
+                       pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
+                                       task_pid_nr(victim), victim->comm,
+                                       task_pid_nr(p), p->comm);
                        continue;
                }
                do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);