genirq: Provide __irq_enter/exit_raw()

Like __irq_enter/exit() but without time accounting. To be used for "empty"
system vectors like the scheduler IPI to avoid the overhead.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20200521202117.671682341@linutronix.de

include/linux/hardirq.h

@@ -37,6 +37,17 @@ static __always_inline void rcu_irq_enter_check_tick(void)
 		lockdep_hardirq_enter();		\
 	} while (0)
 
+/*
+ * Like __irq_enter() without time accounting for fast
+ * interrupts, e.g. reschedule IPI where time accounting
+ * is more expensive than the actual interrupt.
+ */
+#define __irq_enter_raw()				\
+	do {						\
+		preempt_count_add(HARDIRQ_OFFSET);	\
+		lockdep_hardirq_enter();		\
+	} while (0)
+
 /*
  * Enter irq context (on NO_HZ, update jiffies):
  */
@@ -56,6 +67,15 @@ void irq_enter_rcu(void);
 		preempt_count_sub(HARDIRQ_OFFSET);	\
 	} while (0)
 
+/*
+ * Like __irq_exit() without time accounting
+ */
+#define __irq_exit_raw()				\
+	do {						\
+		lockdep_hardirq_exit();			\
+		preempt_count_sub(HARDIRQ_OFFSET);	\
+	} while (0)
+
 /*
  * Exit irq context and process softirqs if needed:
  */