x86/smp: Remove pointless duplicated interrupt code

Two NOP5s are really a good tradeoff vs. the unholy IDT switching mess,
which duplicates code all over the place. The rescheduling interrupt gets
optimized in a later step.

Make the ordering of function call and statistics increment the same as in
other places. Calculate stats first, then do the function call.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20170828064957.222101344@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/hw_irq.h

@@ -49,8 +49,8 @@ extern asmlinkage void call_function_single_interrupt(void);
 #ifdef CONFIG_TRACING
 /* Interrupt handlers registered during init_IRQ */
 extern void trace_reschedule_interrupt(void);
-extern void trace_call_function_interrupt(void);
-extern void trace_call_function_single_interrupt(void);
+#define trace_call_function_interrupt	call_function_interrupt
+#define trace_call_function_single_interrupt	call_function_single_interrupt
 #define trace_thermal_interrupt	thermal_interrupt
 #define trace_threshold_interrupt	threshold_interrupt
 #define trace_deferred_error_interrupt	deferred_error_interrupt

arch/x86/kernel/smp.c

@@ -281,57 +281,28 @@ __visible void __irq_entry smp_trace_reschedule_interrupt(struct pt_regs *regs)
 	 */
 	ipi_entering_ack_irq();
 	trace_reschedule_entry(RESCHEDULE_VECTOR);
-	__smp_reschedule_interrupt();
+	inc_irq_stat(irq_resched_count);
+	scheduler_ipi();
 	trace_reschedule_exit(RESCHEDULE_VECTOR);
 	exiting_irq();
-	/*
-	 * KVM uses this interrupt to force a cpu out of guest mode
-	 */
-}
-
-static inline void __smp_call_function_interrupt(void)
-{
-	generic_smp_call_function_interrupt();
-	inc_irq_stat(irq_call_count);
 }
 
 __visible void __irq_entry smp_call_function_interrupt(struct pt_regs *regs)
-{
-	ipi_entering_ack_irq();
-	__smp_call_function_interrupt();
-	exiting_irq();
-}
-
-__visible void __irq_entry
-smp_trace_call_function_interrupt(struct pt_regs *regs)
 {
 	ipi_entering_ack_irq();
 	trace_call_function_entry(CALL_FUNCTION_VECTOR);
-	__smp_call_function_interrupt();
-	trace_call_function_exit(CALL_FUNCTION_VECTOR);
-	exiting_irq();
-}
-
-static inline void __smp_call_function_single_interrupt(void)
-{
-	generic_smp_call_function_single_interrupt();
 	inc_irq_stat(irq_call_count);
-}
-
-__visible void __irq_entry
-smp_call_function_single_interrupt(struct pt_regs *regs)
-{
-	ipi_entering_ack_irq();
-	__smp_call_function_single_interrupt();
+	generic_smp_call_function_interrupt();
+	trace_call_function_exit(CALL_FUNCTION_VECTOR);
 	exiting_irq();
 }
 
-__visible void __irq_entry
-smp_trace_call_function_single_interrupt(struct pt_regs *regs)
+__visible void __irq_entry smp_call_function_single_interrupt(struct pt_regs *r)
 {
 	ipi_entering_ack_irq();
 	trace_call_function_single_entry(CALL_FUNCTION_SINGLE_VECTOR);
-	__smp_call_function_single_interrupt();
+	inc_irq_stat(irq_call_count);
+	generic_smp_call_function_single_interrupt();
 	trace_call_function_single_exit(CALL_FUNCTION_SINGLE_VECTOR);
 	exiting_irq();
 }