[patch V4 part 5 01/31] genirq: Provide irq_enter/exit_rcu()

[Thomas Gleixner]

irq_enter()/exit() include the RCU handling. To properly separate the RCU
handling provide variants which contain only the non-RCU related
functionality.

Signed-off-by: Thomas Gleixner <t...@linutronix.de>
---
 include/linux/hardirq.h |   13 +++++++++++--
 kernel/softirq.c        |   35 +++++++++++++++++++++++++++--------
 2 files changed, 38 insertions(+), 10 deletions(-)

--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -43,7 +43,11 @@ extern void rcu_nmi_exit(void);
 /*
  * Enter irq context (on NO_HZ, update jiffies):
  */
-extern void irq_enter(void);
+void irq_enter(void);
+/*
+ * Like irq_enter(), but RCU is already watching.
+ */
+void irq_enter_rcu(void);
 
 /*
  * Exit irq context without processing softirqs:
@@ -58,7 +62,12 @@ extern void irq_enter(void);
 /*
  * Exit irq context and process softirqs if needed:
  */
-extern void irq_exit(void);
+void irq_exit(void);
+
+/*
+ * Like irq_exit(), but return with RCU watching.
+ */
+void irq_exit_rcu(void);
 
 #ifndef arch_nmi_enter
 #define arch_nmi_enter()       do { } while (0)
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -339,12 +339,11 @@ asmlinkage __visible void do_softirq(voi
        local_irq_restore(flags);
 }
 
-/*
- * Enter an interrupt context.
+/**
+ * irq_enter_rcu - Enter an interrupt context with RCU watching
  */
-void irq_enter(void)
+void irq_enter_rcu(void)
 {
-       rcu_irq_enter();
        if (is_idle_task(current) && !in_interrupt()) {
                /*
                 * Prevent raise_softirq from needlessly waking up ksoftirqd
@@ -354,10 +353,18 @@ void irq_enter(void)
                tick_irq_enter();
                _local_bh_enable();
        }
-
        __irq_enter();
 }
 
+/**
+ * irq_enter - Enter an interrupt context including RCU update
+ */
+void irq_enter(void)
+{
+       rcu_irq_enter();
+       irq_enter_rcu();
+}
+
 static inline void invoke_softirq(void)
 {
        if (ksoftirqd_running(local_softirq_pending()))
@@ -397,10 +404,12 @@ static inline void tick_irq_exit(void)
 #endif
 }
 
-/*
- * Exit an interrupt context. Process softirqs if needed and possible:
+/**
+ * irq_exit_rcu() - Exit an interrupt context without updating RCU
+ *
+ * Also processes softirqs if needed and possible.
  */
-void irq_exit(void)
+void irq_exit_rcu(void)
 {
 #ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
        local_irq_disable();
@@ -413,6 +422,16 @@ void irq_exit(void)
                invoke_softirq();
 
        tick_irq_exit();
+}
+
+/**
+ * irq_exit - Exit an interrupt context, update RCU and lockdep
+ *
+ * Also processes softirqs if needed and possible.
+ */
+void irq_exit(void)
+{
+       irq_exit_rcu();
        rcu_irq_exit();
         /* must be last! */
        lockdep_hardirq_exit();