1 files changed, 52 insertions, 0 deletions

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 1a7a4ef04e27..6e999c88c503 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -27,6 +27,7 @@
 #include <linux/notifier.h>
 
 int sysctl_panic_on_oom;
+static DEFINE_MUTEX(zone_scan_mutex);
 /* #define DEBUG */
 
 /**
@@ -374,6 +375,57 @@ int unregister_oom_notifier(struct notifier_block *nb)
 }
 EXPORT_SYMBOL_GPL(unregister_oom_notifier);
 
+/*
+ * 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);
+}
+
 /**
  * out_of_memory - kill the "best" process when we run out of memory
  *