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-rw-r--r--include/linux/oom.h1
-rw-r--r--mm/ksm.c3
-rw-r--r--mm/oom_kill.c19
-rw-r--r--mm/swapfile.c2
4 files changed, 23 insertions, 2 deletions
diff --git a/include/linux/oom.h b/include/linux/oom.h
index 13b7b02e599a..6f9d04a85336 100644
--- a/include/linux/oom.h
+++ b/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/mm/ksm.c b/mm/ksm.c
index 9a68b0cf0a1c..310544a379ae 100644
--- a/mm/ksm.c
+++ b/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/mm/oom_kill.c b/mm/oom_kill.c
index 2b97e8f04607..e916168b6e0a 100644
--- a/mm/oom_kill.c
+++ b/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/mm/swapfile.c b/mm/swapfile.c
index 17bc224bce68..c9d654009125 100644
--- a/mm/swapfile.c
+++ b/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) {
/*