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[patch V3 15/44] x86/smp: Use static key for reschedule interrupt tracing

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It's worth to avoid the extra irq_enter()/irq_exit() pair in the case that
the reschedule interrupt tracepoints are disabled.

Use the static key which indicates that exception tracing is enabled. For
now this key is global. It will be optimized in a later step.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 arch/x86/include/asm/hw_irq.h |    2 +-
 arch/x86/kernel/smp.c         |   40 +++++++++++++++-------------------------
 2 files changed, 16 insertions(+), 26 deletions(-)

--- a/arch/x86/include/asm/hw_irq.h
+++ b/arch/x86/include/asm/hw_irq.h
@@ -48,7 +48,7 @@ extern asmlinkage void call_function_sin
 
 #ifdef CONFIG_TRACING
 /* Interrupt handlers registered during init_IRQ */
-extern void trace_reschedule_interrupt(void);
+#define trace_reschedule_interrupt	reschedule_interrupt
 #define trace_call_function_interrupt	call_function_interrupt
 #define trace_call_function_single_interrupt	call_function_single_interrupt
 #define trace_thermal_interrupt	thermal_interrupt
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -254,37 +254,27 @@ static void native_stop_other_cpus(int w
 }
 
 /*
- * Reschedule call back.
+ * Reschedule call back. KVM uses this interrupt to force a cpu out of
+ * guest mode
  */
-static inline void __smp_reschedule_interrupt(void)
-{
-	inc_irq_stat(irq_resched_count);
-	scheduler_ipi();
-}
-
 __visible void __irq_entry smp_reschedule_interrupt(struct pt_regs *regs)
 {
 	ack_APIC_irq();
-	__smp_reschedule_interrupt();
-	/*
-	 * KVM uses this interrupt to force a cpu out of guest mode
-	 */
-}
-
-__visible void __irq_entry smp_trace_reschedule_interrupt(struct pt_regs *regs)
-{
-	/*
-	 * Need to call irq_enter() before calling the trace point.
-	 * __smp_reschedule_interrupt() calls irq_enter/exit() too (in
-	 * scheduler_ipi(). This is OK, since those functions are allowed
-	 * to nest.
-	 */
-	ipi_entering_ack_irq();
-	trace_reschedule_entry(RESCHEDULE_VECTOR);
 	inc_irq_stat(irq_resched_count);
+
+	if (trace_irqvectors_enabled()) {
+		/*
+		 * scheduler_ipi() might call irq_enter() as well, but
+		 * nested calls are fine.
+		 */
+		irq_enter();
+		trace_reschedule_entry(RESCHEDULE_VECTOR);
+		scheduler_ipi();
+		trace_reschedule_exit(RESCHEDULE_VECTOR);
+		irq_exit();
+		return;
+	}
 	scheduler_ipi();
-	trace_reschedule_exit(RESCHEDULE_VECTOR);
-	exiting_irq();
 }
 
 __visible void __irq_entry smp_call_function_interrupt(struct pt_regs *regs)

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[patch V3 00/44] x86: Cleanup IDT code Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
  [patch V3 13/44] x86/mce: Remove duplicated tracing interrupt code Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/mce: Remove duplicated tracing interrupt code tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:20 +0200
  [patch V3 05/44] x86/boot: Move EISA setup to a proper place Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/boot: Move EISA setup to a separate file tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:20 +0200
  [patch V3 15/44] x86/smp: Use static key for reschedule interrupt  tracing Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/smp: Use static key for reschedule interrupt  tracing tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:20 +0200
  [patch V3 12/44] x86/irqwork: Get rid of duplicated tracing interrupt  code Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/irqwork: Get rid of duplicated tracing interrupt  code tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:20 +0200
  [patch V3 10/44] x86/irq: Get rid of duplicated  trace_x86_platform_ipi() code Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/irq: Get rid of duplicated  trace_x86_platform_ipi() code tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:20 +0200
  [patch V3 06/44] x86/tracing: Introduce a static key for exception  tracing Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/tracing: Introduce a static key for exception  tracing tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:20 +0200
  [patch V3 08/44] x86/apic: Remove the duplicated tracing version of  local_timer_interrupt Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/apic: Remove the duplicated tracing version of  local_timer_interrupt() tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:20 +0200
  [patch V3 14/44] x86/smp: Remove pointless duplicated interrupt code Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/smp: Remove pointless duplicated interrupt code tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:20 +0200
  [patch V3 04/44] x86/irq: Remove duplicated used_vectors definition Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/irq: Remove duplicated used_vectors definition tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:20 +0200
  [patch V3 03/44] x86/irq: Get rid of the first_system_vector bogisity Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/irq: Get rid of the 'first_system_vector'  indirection bogosity tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:20 +0200
  [patch V3 28/44] x86/idt: Create file for IDT related code Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 09:10 +0200
    [tip:x86/apic] x86/idt: Create file for IDT related code tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2017-08-29 13:30 +0200

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