rk: revert 20f3d0b+v3.0.66 to v3.0

[firefly-linux-kernel-4.4.55.git] / include / linux / cpuset.h

diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index 7a7e5fd2a27784e3307e3351c92abd4240aba2db..e9eaec522655c4da77f55fefb851564c31cae711 100644 (file)
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -89,33 +89,42 @@ extern void rebuild_sched_domains(void);
 extern void cpuset_print_task_mems_allowed(struct task_struct *p);
 
 /*
- * get_mems_allowed is required when making decisions involving mems_allowed
- * such as during page allocation. mems_allowed can be updated in parallel
- * and depending on the new value an operation can fail potentially causing
- * process failure. A retry loop with get_mems_allowed and put_mems_allowed
- * prevents these artificial failures.
+ * reading current mems_allowed and mempolicy in the fastpath must protected
+ * by get_mems_allowed()
  */
-static inline unsigned int get_mems_allowed(void)
+static inline void get_mems_allowed(void)
 {
-       return read_seqcount_begin(&current->mems_allowed_seq);
+       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();
 }
 
-/*
- * If this returns false, the operation that took place after get_mems_allowed
- * may have failed. It is up to the caller to retry the operation if
- * appropriate.
- */
-static inline bool put_mems_allowed(unsigned int seq)
+static inline void put_mems_allowed(void)
 {
-       return !read_seqcount_retry(&current->mems_allowed_seq, seq);
+       /*
+        * 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);
-       write_seqcount_begin(&current->mems_allowed_seq);
        current->mems_allowed = nodemask;
-       write_seqcount_end(&current->mems_allowed_seq);
        task_unlock(current);
 }
 
@@ -225,14 +234,12 @@ static inline void set_mems_allowed(nodemask_t nodemask)
 {
 }
 
-static inline unsigned int get_mems_allowed(void)
+static inline void get_mems_allowed(void)
 {
-       return 0;
 }
 
-static inline bool put_mems_allowed(unsigned int seq)
+static inline void put_mems_allowed(void)
 {
-       return true;
 }
 
 #endif /* !CONFIG_CPUSETS */