rcu: fix misplaced mb() in rcu_enter/exit_nohz()

[sfrench/cifs-2.6.git] / include / linux / rcupreempt.h

diff --git a/include/linux/rcupreempt.h b/include/linux/rcupreempt.h
index ece8eb3e4151411be2df54326405d03f880ab38d..d038aa6e5ee1b4dd64cba0e8e193439c16f010f7 100644 (file)
--- a/include/linux/rcupreempt.h
+++ b/include/linux/rcupreempt.h
@@ -46,8 +46,8 @@
 #define rcu_bh_qsctr_inc(cpu)
 #define call_rcu_bh(head, rcu) call_rcu(head, rcu)
 
-extern void __rcu_read_lock(void);
-extern void __rcu_read_unlock(void);
+extern void __rcu_read_lock(void)      __acquires(RCU);
+extern void __rcu_read_unlock(void)    __releases(RCU);
 extern int rcu_pending(int cpu);
 extern int rcu_needs_cpu(int cpu);
 
@@ -82,5 +82,27 @@ extern struct rcupreempt_trace *rcupreempt_trace_cpu(int cpu);
 
 struct softirq_action;
 
+#ifdef CONFIG_NO_HZ
+DECLARE_PER_CPU(long, dynticks_progress_counter);
+
+static inline void rcu_enter_nohz(void)
+{
+       smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
+       __get_cpu_var(dynticks_progress_counter)++;
+       WARN_ON(__get_cpu_var(dynticks_progress_counter) & 0x1);
+}
+
+static inline void rcu_exit_nohz(void)
+{
+       __get_cpu_var(dynticks_progress_counter)++;
+       smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
+       WARN_ON(!(__get_cpu_var(dynticks_progress_counter) & 0x1));
+}
+
+#else /* CONFIG_NO_HZ */
+#define rcu_enter_nohz()       do { } while (0)
+#define rcu_exit_nohz()                do { } while (0)
+#endif /* CONFIG_NO_HZ */
+
 #endif /* __KERNEL__ */
 #endif /* __LINUX_RCUPREEMPT_H */