From f99efe3f04efa0fb05dcc2d0ad2d987d60ee6c12 Mon Sep 17 00:00:00 2001
From: David Rientjes <rientjes@google.com>
Date: Mon, 31 Oct 2011 17:07:18 -0700
Subject: [PATCH] --- yaml --- r: 272118 b: refs/heads/master c:
 43362a4977e37db46f86f7e6ab935f0006956632 h: refs/heads/master v: v3

---
 [refs]                    |  2 +-
 trunk/include/linux/oom.h |  1 +
 trunk/mm/ksm.c            |  3 ++-
 trunk/mm/oom_kill.c       | 19 +++++++++++++++++++
 trunk/mm/swapfile.c       |  2 +-
 5 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/[refs] b/[refs]
index 74e6723f0b8f..c496720262c9 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: c9f01245b6a7d77d17deaa71af10f6aca14fa24e
+refs/heads/master: 43362a4977e37db46f86f7e6ab935f0006956632
diff --git a/trunk/include/linux/oom.h b/trunk/include/linux/oom.h
index 13b7b02e599a..6f9d04a85336 100644
--- a/trunk/include/linux/oom.h
+++ b/trunk/include/linux/oom.h
@@ -40,6 +40,7 @@ enum oom_constraint {
 	CONSTRAINT_MEMCG,
 };
 
+extern void compare_swap_oom_score_adj(int old_val, int new_val);
 extern int test_set_oom_score_adj(int new_val);
 
 extern unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem,
diff --git a/trunk/mm/ksm.c b/trunk/mm/ksm.c
index 9a68b0cf0a1c..310544a379ae 100644
--- a/trunk/mm/ksm.c
+++ b/trunk/mm/ksm.c
@@ -1905,7 +1905,8 @@ static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr,
 
 			oom_score_adj = test_set_oom_score_adj(OOM_SCORE_ADJ_MAX);
 			err = unmerge_and_remove_all_rmap_items();
-			test_set_oom_score_adj(oom_score_adj);
+			compare_swap_oom_score_adj(OOM_SCORE_ADJ_MAX,
+								oom_score_adj);
 			if (err) {
 				ksm_run = KSM_RUN_STOP;
 				count = err;
diff --git a/trunk/mm/oom_kill.c b/trunk/mm/oom_kill.c
index 2b97e8f04607..e916168b6e0a 100644
--- a/trunk/mm/oom_kill.c
+++ b/trunk/mm/oom_kill.c
@@ -39,6 +39,25 @@ int sysctl_oom_kill_allocating_task;
 int sysctl_oom_dump_tasks = 1;
 static DEFINE_SPINLOCK(zone_scan_lock);
 
+/*
+ * compare_swap_oom_score_adj() - compare and swap current's oom_score_adj
+ * @old_val: old oom_score_adj for compare
+ * @new_val: new oom_score_adj for swap
+ *
+ * Sets the oom_score_adj value for current to @new_val iff its present value is
+ * @old_val.  Usually used to reinstate a previous value to prevent racing with
+ * userspacing tuning the value in the interim.
+ */
+void compare_swap_oom_score_adj(int old_val, int new_val)
+{
+	struct sighand_struct *sighand = current->sighand;
+
+	spin_lock_irq(&sighand->siglock);
+	if (current->signal->oom_score_adj == old_val)
+		current->signal->oom_score_adj = new_val;
+	spin_unlock_irq(&sighand->siglock);
+}
+
 /**
  * test_set_oom_score_adj() - set current's oom_score_adj and return old value
  * @new_val: new oom_score_adj value
diff --git a/trunk/mm/swapfile.c b/trunk/mm/swapfile.c
index 17bc224bce68..c9d654009125 100644
--- a/trunk/mm/swapfile.c
+++ b/trunk/mm/swapfile.c
@@ -1617,7 +1617,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 
 	oom_score_adj = test_set_oom_score_adj(OOM_SCORE_ADJ_MAX);
 	err = try_to_unuse(type);
-	test_set_oom_score_adj(oom_score_adj);
+	compare_swap_oom_score_adj(OOM_SCORE_ADJ_MAX, oom_score_adj);
 
 	if (err) {
 		/*