1 files changed, 43 insertions, 0 deletions

diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index a73454aec333..20b51cab6593 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -86,9 +86,44 @@ extern void rebuild_sched_domains(void);
 
 extern void cpuset_print_task_mems_allowed(struct task_struct *p);
 
+/*
+ * reading current mems_allowed and mempolicy in the fastpath must protected
+ * by get_mems_allowed()
+ */
+static inline void get_mems_allowed(void)
+{
+        current->mems_allowed_change_disable++;
+
+        /*
+         * ensure that reading mems_allowed and mempolicy happens after the
+         * update of ->mems_allowed_change_disable.
+         *
+         * the write-side task finds ->mems_allowed_change_disable is not 0,
+         * and knows the read-side task is reading mems_allowed or mempolicy,
+         * so it will clear old bits lazily.
+         */
+        smp_mb();
+}
+
+static inline void put_mems_allowed(void)
+{
+        /*
+         * ensure that reading mems_allowed and mempolicy before reducing
+         * mems_allowed_change_disable.
+         *
+         * the write-side task will know that the read-side task is still
+         * reading mems_allowed or mempolicy, don't clears old bits in the
+         * nodemask.
+         */
+        smp_mb();
+        --ACCESS_ONCE(current->mems_allowed_change_disable);
+}
+
 static inline void set_mems_allowed(nodemask_t nodemask)
 {
+        task_lock(current);
         current->mems_allowed = nodemask;
+        task_unlock(current);
 }
 
 #else /* !CONFIG_CPUSETS */
@@ -187,6 +222,14 @@ static inline void set_mems_allowed(nodemask_t nodemask)
 {
 }
 
+static inline void get_mems_allowed(void)
+{
+}
+
+static inline void put_mems_allowed(void)
+{
+}
+
 #endif /* !CONFIG_CPUSETS */
 
 #endif /* _LINUX_CPUSET_H */