"Tree RCU": scalable classic RCU implementation

[safe/jmp/linux-2.6] / include / linux / hardirq.h

diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 2961ec7..9b70b92 100644 (file)
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -72,17 +72,26 @@
 #define in_softirq()           (softirq_count())
 #define in_interrupt()         (irq_count())
 
-#define in_atomic()            ((preempt_count() & ~PREEMPT_ACTIVE) != 0)
-
-#ifdef CONFIG_PREEMPT
+#if defined(CONFIG_PREEMPT)
+# define PREEMPT_INATOMIC_BASE kernel_locked()
 # define PREEMPT_CHECK_OFFSET 1
 #else
+# define PREEMPT_INATOMIC_BASE 0
 # define PREEMPT_CHECK_OFFSET 0
 #endif
 
 /*
+ * Are we running in atomic context?  WARNING: this macro cannot
+ * always detect atomic context; in particular, it cannot know about
+ * held spinlocks in non-preemptible kernels.  Thus it should not be
+ * used in the general case to determine whether sleeping is possible.
+ * Do not use in_atomic() in driver code.
+ */
+#define in_atomic()    ((preempt_count() & ~PREEMPT_ACTIVE) != PREEMPT_INATOMIC_BASE)
+
+/*
  * Check whether we were atomic before we did preempt_disable():
- * (used by the scheduler)
+ * (used by the scheduler, *after* releasing the kernel lock)
  */
 #define in_atomic_preempt_off() \
                ((preempt_count() & ~PREEMPT_ACTIVE) != PREEMPT_CHECK_OFFSET)
@@ -109,6 +118,18 @@ static inline void account_system_vtime(struct task_struct *tsk)
 }
 #endif
 
+#if defined(CONFIG_NO_HZ) && !defined(CONFIG_CLASSIC_RCU)
+extern void rcu_irq_enter(void);
+extern void rcu_irq_exit(void);
+extern void rcu_nmi_enter(void);
+extern void rcu_nmi_exit(void);
+#else
+# define rcu_irq_enter() do { } while (0)
+# define rcu_irq_exit() do { } while (0)
+# define rcu_nmi_enter() do { } while (0)
+# define rcu_nmi_exit() do { } while (0)
+#endif /* #if defined(CONFIG_NO_HZ) && !defined(CONFIG_CLASSIC_RCU) */
+
 /*
  * It is safe to do non-atomic ops on ->hardirq_context,
  * because NMI handlers may not preempt and the ops are
@@ -142,7 +163,7 @@ extern void irq_enter(void);
  */
 extern void irq_exit(void);
 
-#define nmi_enter()            do { lockdep_off(); __irq_enter(); } while (0)
-#define nmi_exit()             do { __irq_exit(); lockdep_on(); } while (0)
+#define nmi_enter()            do { lockdep_off(); rcu_nmi_enter(); __irq_enter(); } while (0)
+#define nmi_exit()             do { __irq_exit(); rcu_nmi_exit(); lockdep_on(); } while (0)
 
 #endif /* LINUX_HARDIRQ_H */