rcu: Don't redundantly disable irqs in rcu_irq_{enter,exit}()
This commit replaces a local_irq_save()/local_irq_restore() pair with
a lockdep assertion that interrupts are already disabled. This should
remove the corresponding overhead from the interrupt entry/exit fastpaths.
This change was inspired by the fact that Iftekhar Ahmed's mutation
testing showed that removing rcu_irq_enter()'s call to local_ird_restore()
had no effect, which might indicate that interrupts were always enabled
anyway.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index a0189ba..f2b667d 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -379,9 +379,9 @@
*/
#define RCU_NONIDLE(a) \
do { \
- rcu_irq_enter(); \
+ rcu_irq_enter_irqson(); \
do { a; } while (0); \
- rcu_irq_exit(); \
+ rcu_irq_exit_irqson(); \
} while (0)
/*
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 4c1aaf9..64809ae 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -181,6 +181,14 @@
{
}
+static inline void rcu_irq_exit_irqson(void)
+{
+}
+
+static inline void rcu_irq_enter_irqson(void)
+{
+}
+
static inline void rcu_irq_exit(void)
{
}
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 9d3eda3..ad1eda9 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -97,6 +97,8 @@
void rcu_idle_exit(void);
void rcu_irq_enter(void);
void rcu_irq_exit(void);
+void rcu_irq_enter_irqson(void);
+void rcu_irq_exit_irqson(void);
void exit_rcu(void);
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 696a339c..7834a8a 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -171,8 +171,8 @@
TP_PROTO(data_proto), \
TP_ARGS(data_args), \
TP_CONDITION(cond), \
- rcu_irq_enter(), \
- rcu_irq_exit()); \
+ rcu_irq_enter_irqson(), \
+ rcu_irq_exit_irqson()); \
}
#else
#define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args)