+/*
+ * 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)
+{
+ struct zone **z;
+ int ret = 1;
+
+ z = zonelist->zones;
+
+ mutex_lock(&zone_scan_mutex);
+ do {
+ if (zone_is_oom_locked(*z)) {
+ ret = 0;
+ goto out;
+ }
+ } while (*(++z) != NULL);
+
+ /*
+ * Lock each zone in the zonelist under zone_scan_mutex so a parallel
+ * invocation of try_set_zone_oom() doesn't succeed when it shouldn't.
+ */
+ z = zonelist->zones;
+ do {
+ zone_set_flag(*z, ZONE_OOM_LOCKED);
+ } while (*(++z) != NULL);
+out:
+ mutex_unlock(&zone_scan_mutex);
+ 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)
+{
+ struct zone **z;
+
+ z = zonelist->zones;
+
+ mutex_lock(&zone_scan_mutex);
+ do {
+ zone_clear_flag(*z, ZONE_OOM_LOCKED);
+ } while (*(++z) != NULL);
+ mutex_unlock(&zone_scan_mutex);
+}
+