4 files changed, 67 insertions, 1 deletions

diff --git a/include/linux/oom.h b/include/linux/oom.h
index 647395a1a550..e8d6e1058723 100644
--- a/include/linux/oom.h
+++ b/include/linux/oom.h
@@ -50,6 +50,9 @@ static inline bool oom_task_origin(const struct task_struct *p)
 extern unsigned long oom_badness(struct task_struct *p,
                 struct mem_cgroup *memcg, const nodemask_t *nodemask,
                 unsigned long totalpages);
+
+extern int oom_kills_count(void);
+extern void note_oom_kill(void);
 extern void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
                              unsigned int points, unsigned long totalpages,
                              struct mem_cgroup *memcg, nodemask_t *nodemask,
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 7b323221b9ee..5cc588c1abab 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -108,6 +108,28 @@ static int try_to_freeze_tasks(bool user_only)
         return todo ? -EBUSY : 0;
 }
 
+/*
+ * Returns true if all freezable tasks (except for current) are frozen already
+ */
+static bool check_frozen_processes(void)
+{
+        struct task_struct *g, *p;
+        bool ret = true;
+
+        read_lock(&tasklist_lock);
+        for_each_process_thread(g, p) {
+                if (p != current && !freezer_should_skip(p) &&
+                    !frozen(p)) {
+                        ret = false;
+                        goto done;
+                }
+        }
+done:
+        read_unlock(&tasklist_lock);
+
+        return ret;
+}
+
 /**
  * freeze_processes - Signal user space processes to enter the refrigerator.
  * The current thread will not be frozen.  The same process that calls
@@ -118,6 +140,7 @@ static int try_to_freeze_tasks(bool user_only)
 int freeze_processes(void)
 {
         int error;
+        int oom_kills_saved;
 
         error = __usermodehelper_disable(UMH_FREEZING);
         if (error)
@@ -132,12 +155,27 @@ int freeze_processes(void)
         pm_wakeup_clear();
         printk("Freezing user space processes ... ");
         pm_freezing = true;
+        oom_kills_saved = oom_kills_count();
         error = try_to_freeze_tasks(true);
         if (!error) {
-                printk("done.");
                 __usermodehelper_set_disable_depth(UMH_DISABLED);
                 oom_killer_disable();
+
+                /*
+                 * There might have been an OOM kill while we were
+                 * freezing tasks and the killed task might be still
+                 * on the way out so we have to double check for race.
+                 */
+                if (oom_kills_count() != oom_kills_saved &&
+                                !check_frozen_processes()) {
+                        __usermodehelper_set_disable_depth(UMH_ENABLED);
+                        printk("OOM in progress.");
+                        error = -EBUSY;
+                        goto done;
+                }
+                printk("done.");
         }
+done:
         printk("\n");
         BUG_ON(in_atomic());
 
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index bbf405a3a18f..5340f6b91312 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -404,6 +404,23 @@ static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
                 dump_tasks(memcg, nodemask);
 }
 
+/*
+ * Number of OOM killer invocations (including memcg OOM killer).
+ * Primarily used by PM freezer to check for potential races with
+ * OOM killed frozen task.
+ */
+static atomic_t oom_kills = ATOMIC_INIT(0);
+
+int oom_kills_count(void)
+{
+        return atomic_read(&oom_kills);
+}
+
+void note_oom_kill(void)
+{
+        atomic_inc(&oom_kills);
+}
+
 #define K(x) ((x) << (PAGE_SHIFT-10))
 /*
  * Must be called while holding a reference to p, which will be released upon
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 736d8e1b6381..9cd36b822444 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2252,6 +2252,14 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
         }
 
         /*
+         * PM-freezer should be notified that there might be an OOM killer on
+         * its way to kill and wake somebody up. This is too early and we might
+         * end up not killing anything but false positives are acceptable.
+         * See freeze_processes.
+         */
+        note_oom_kill();
+
+        /*
          * Go through the zonelist yet one more time, keep very high watermark
          * here, this is only to catch a parallel oom killing, we must fail if
          * we're still under heavy pressure.