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Groups > linux.kernel > #1720464

[patch V2 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 V2 00/44] x86: Cleanup IDT code Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:00 +0200
  [patch V2 23/44] x86/percpu: Use static initializer for GDT entry Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:00 +0200
  [patch V2 33/44] x86/idt: Move early IDT setup out of 32bit asm Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:00 +0200
  [patch V2 44/44] x86/idt: Hide set_intr_gate() Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:00 +0200
  [patch V2 38/44] x86/idt: Move regular trap init to tables Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:00 +0200
  [patch V2 02/44] x86/irq: Unexport used_vectors Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:00 +0200
  [patch V2 21/44] x86/tracing: Build tracepoints only when they are  used Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:00 +0200
  [patch V2 04/44] x86/irq: Remove duplicated used_vectors definition Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:00 +0200
  [patch V2 39/44] x86/idt: Move APIC gate initialization to tables Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:00 +0200
  [patch V2 11/44] x86/apic: Remove the duplicated tracing versions of  interrupts Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:00 +0200
  [patch V2 29/44] x86/idt: Move 32bit idt_descr to C code Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 16/44] x86/idt: Remove tracing idt completely Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 05/44] x86/boot: Move EISA setup to a proper place Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 17/44] x86/idt: Cleanup the i386 low level entry macros Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 26/44] x86/gdt: Use bitfields for initialization Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 06/44] x86/tracing: Introduce a static key for exception  tracing Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 18/44] x86/tracing: Disentangle pagefault and resched IPI  tracing key Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 12/44] x86/irqwork: Get rid of duplicated tracing interrupt  code Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 20/44] x86/irq_work: Make it depend on APIC Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 09/44] x86/apic: Use this_cpu_ptr in local_timer_interrupt Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 27/44] x86/ldttss: Cleanup 32bit descriptors Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 13/44] x86/mce: Remove duplicated tracing interrupt code Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 36/44] x86/idt: Move debug stack init to table based Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 15/44] x86/smp: Use static key for reschedule interrupt  tracing Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 03/44] x86/irq: Get rid of the first_system_vector bogisity Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 14/44] x86/smp: Remove pointless duplicated interrupt code Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 28/44] x86/idt: Create file for IDT related code Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 07/44] x86/traps: Simplify pagefault tracing logic Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 37/44] x86/idt: Move ist stack based traps to table init Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 10/44] x86/irq: Get rid of duplicated  trace_x86_platform_ipi() code Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 31/44] x86/idt: Consolidate IDT invalidation Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 25/44] x86: Replace access to desc_struct:a/b fields Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
    Re: [patch V2 25/44] x86: Replace access to desc_struct:a/b fields Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-08-26 04:20 +0200
  [patch V2 34/44] x86/idt: Prepare for table based init Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 22/44] x86/idt: Unify gate_struct handling for 32/64bit Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 32/44] x86/idt: Move early IDT handler setup to IDT code Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 08/44] x86/apic: Remove the duplicated tracing version of  local_timer_interrupt Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 30/44] x86/idt: Remove unused set_trap_gate() Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 24/44] x86/fpu: Use bitfield accessors for desc_struct Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:10 +0200
  [patch V2 01/44] x86/irq: Remove vector_used_by_percpu_irq() Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 00:20 +0200

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