+/*
+ * Try to acquire the OOM killer lock for the zones in zonelist. Returns zero
+ * if a parallel OOM killing is already taking place that includes a zone in
+ * the zonelist. Otherwise, locks all zones in the zonelist and returns 1.
+ */
+int try_set_zone_oom(struct zonelist *zonelist, gfp_t gfp_mask)
+{
+ struct zoneref *z;
+ struct zone *zone;
+ int ret = 1;
+
+ spin_lock(&zone_scan_lock);
+ for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
+ if (zone_is_oom_locked(zone)) {
+ ret = 0;
+ goto out;
+ }
+ }
+
+ for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
+ /*
+ * Lock each zone in the zonelist under zone_scan_lock so a
+ * parallel invocation of try_set_zone_oom() doesn't succeed
+ * when it shouldn't.
+ */
+ zone_set_flag(zone, ZONE_OOM_LOCKED);
+ }
+
+out:
+ spin_unlock(&zone_scan_lock);
+ return ret;
+}
+
+/*
+ * Clears the ZONE_OOM_LOCKED flag for all zones in the zonelist so that failed
+ * allocation attempts with zonelists containing them may now recall the OOM
+ * killer, if necessary.
+ */
+void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
+{
+ struct zoneref *z;
+ struct zone *zone;
+
+ spin_lock(&zone_scan_lock);
+ for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
+ zone_clear_flag(zone, ZONE_OOM_LOCKED);
+ }
+ spin_unlock(&zone_scan_lock);
+}
+
+/*
+ * Must be called with tasklist_lock held for read.
+ */
+static void __out_of_memory(gfp_t gfp_mask, int order)
+{
+ struct task_struct *p;
+ unsigned long points;
+
+ if (sysctl_oom_kill_allocating_task)
+ if (!oom_kill_process(current, gfp_mask, order, 0, NULL,
+ "Out of memory (oom_kill_allocating_task)"))
+ return;
+retry:
+ /*
+ * Rambo mode: Shoot down a process and hope it solves whatever
+ * issues we may have.
+ */
+ p = select_bad_process(&points, NULL);
+
+ if (PTR_ERR(p) == -1UL)
+ return;
+
+ /* Found nothing?!?! Either we hang forever, or we panic. */
+ if (!p) {
+ read_unlock(&tasklist_lock);
+ dump_header(gfp_mask, order, NULL);
+ panic("Out of memory and no killable processes...\n");
+ }
+
+ if (oom_kill_process(p, gfp_mask, order, points, NULL,
+ "Out of memory"))
+ goto retry;
+}
+
+/*
+ * pagefault handler calls into here because it is out of memory but
+ * doesn't know exactly how or why.
+ */
+void pagefault_out_of_memory(void)
+{
+ unsigned long freed = 0;
+
+ blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
+ if (freed > 0)
+ /* Got some memory back in the last second. */
+ return;
+
+ /*
+ * If this is from memcg, oom-killer is already invoked.
+ * and not worth to go system-wide-oom.
+ */
+ if (mem_cgroup_oom_called(current))
+ goto rest_and_return;
+
+ if (sysctl_panic_on_oom)
+ panic("out of memory from page fault. panic_on_oom is selected.\n");
+
+ read_lock(&tasklist_lock);
+ __out_of_memory(0, 0); /* unknown gfp_mask and order */
+ read_unlock(&tasklist_lock);
+
+ /*
+ * Give "p" a good chance of killing itself before we
+ * retry to allocate memory.
+ */
+rest_and_return:
+ if (!test_thread_flag(TIF_MEMDIE))
+ schedule_timeout_uninterruptible(1);
+}
+