+enum oom_scan_t {
+ OOM_SCAN_OK, /* scan thread and find its badness */
+ OOM_SCAN_CONTINUE, /* do not consider thread for oom kill */
+ OOM_SCAN_ABORT, /* abort the iteration and return */
+ OOM_SCAN_SELECT, /* always select this thread first */
+};
+
+static enum oom_scan_t oom_scan_process_thread(struct task_struct *task,
+ struct mem_cgroup *memcg, unsigned long totalpages,
+ const nodemask_t *nodemask, bool force_kill)
+{
+ if (task->exit_state)
+ return OOM_SCAN_CONTINUE;
+ if (oom_unkillable_task(task, memcg, nodemask))
+ return OOM_SCAN_CONTINUE;
+
+ /*
+ * This task already has access to memory reserves and is being killed.
+ * Don't allow any other task to have access to the reserves.
+ */
+ if (test_tsk_thread_flag(task, TIF_MEMDIE)) {
+ if (unlikely(frozen(task)))
+ __thaw_task(task);
+ if (!force_kill)
+ return OOM_SCAN_ABORT;
+ }
+ if (!task->mm)
+ return OOM_SCAN_CONTINUE;
+
+ if (task->flags & PF_EXITING) {
+ /*
+ * If task is current and is in the process of releasing memory,
+ * allow the "kill" to set TIF_MEMDIE, which will allow it to
+ * access memory reserves. Otherwise, it may stall forever.
+ *
+ * The iteration isn't broken here, however, in case other
+ * threads are found to have already been oom killed.
+ */
+ if (task == current)
+ return OOM_SCAN_SELECT;
+ else if (!force_kill) {
+ /*
+ * If this task is not being ptraced on exit, then wait
+ * for it to finish before killing some other task
+ * unnecessarily.
+ */
+ if (!(task->group_leader->ptrace & PT_TRACE_EXIT))
+ return OOM_SCAN_ABORT;
+ }
+ }
+ return OOM_SCAN_OK;
+}
+