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Re: [patch 14/41] x86/smp: Use static key for reschedule interrupt tracing

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On Fri, 25 Aug 2017 12:31:17 +0200
Thomas Gleixner <tglx@linutronix.de> wrote:


> -__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);
> +	if (trace_irqvectors_enabled()) {
> +		/*
> +		 * scheduler_ipi() might call irq_enter() as well, but
> +		 * nested calls are fine.
> +		 */
> +		irq_enter();
> +		trace_reschedule_entry(RESCHEDULE_VECTOR);
> +	}
> +
>  	inc_irq_stat(irq_resched_count);
>  	scheduler_ipi();
> -	trace_reschedule_exit(RESCHEDULE_VECTOR);
> -	exiting_irq();
> +
> +	if (trace_irqvectors_enabled()) {
> +		trace_reschedule_exit(RESCHEDULE_VECTOR);
> +		irq_exit();

This is racy. If the static key gets changed on one and not the other,
we lose the irq_enter/irq_exit match.

-- Steve


> +	}
>  }
>  
>  __visible void __irq_entry smp_call_function_interrupt(struct pt_regs *regs)
> 

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Thread

[patch 00/41] x86: Cleanup IDT code Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
  [patch 01/41] x86/irq: Remove vector_used_by_percpu_irq() Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
  [patch 26/41] x86/idt: Consolidate IDT invalidation Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
  [patch 06/41] x86/traps: Simplify pagefault tracing logic Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
    Re: [patch 06/41] x86/traps: Simplify pagefault tracing logic Andy Lutomirski <luto@kernel.org> - 2017-08-25 17:00 +0200
    Re: [patch 06/41] x86/traps: Simplify pagefault tracing logic Steven Rostedt <rostedt@goodmis.org> - 2017-08-25 17:20 +0200
      Re: [patch 06/41] x86/traps: Simplify pagefault tracing logic Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 17:20 +0200
  [patch 07/41] x86/apic: Remove the duplicated tracing version of  local_timer_interrupt Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
    Re: [patch 07/41] x86/apic: Remove the duplicated tracing version  of local_timer_interrupt Steven Rostedt <rostedt@goodmis.org> - 2017-08-25 17:30 +0200
  [patch 14/41] x86/smp: Use static key for reschedule interrupt tracing Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
    Re: [patch 14/41] x86/smp: Use static key for reschedule interrupt  tracing Steven Rostedt <rostedt@goodmis.org> - 2017-08-25 21:50 +0200
      Re: [patch 14/41] x86/smp: Use static key for reschedule interrupt  tracing Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 22:10 +0200
        Re: [patch 14/41] x86/smp: Use static key for reschedule interrupt  tracing Steven Rostedt <rostedt@goodmis.org> - 2017-08-25 23:20 +0200
  [patch 05/41] x86/tracing: Introduce a static key for exception  tracing Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
    Re: [patch 05/41] x86/tracing: Introduce a static key for exception  tracing Steven Rostedt <rostedt@goodmis.org> - 2017-08-25 17:30 +0200
  [patch 10/41] x86/apic: Remove the duplicated tracing versions of  interrupts Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
    Re: [patch 10/41] x86/apic: Remove the duplicated tracing versions  of interrupts Steven Rostedt <rostedt@goodmis.org> - 2017-08-25 17:50 +0200
      Re: [patch 10/41] x86/apic: Remove the duplicated tracing versions  of interrupts Peter Zijlstra <peterz@infradead.org> - 2017-08-28 10:00 +0200
  [patch 11/41] x86/irqwork: Get rid of duplicated tracing interrupt  code Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
    Re: [patch 11/41] x86/irqwork: Get rid of duplicated tracing  interrupt code Steven Rostedt <rostedt@goodmis.org> - 2017-08-25 18:00 +0200
  [patch 23/41] x86/idt: Create file for IDT related code Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
  [patch 03/41] x86/irq: Move ifdeffery to header file Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
    Re: [patch 03/41] x86/irq: Move ifdeffery to header file Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 14:50 +0200
  [patch 24/41] x86/idt: Move 32bit idt_descr to C code Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
  [patch 16/41] x86/tracing: Disentangle pagefault and resched IPI  tracing key Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
  [patch 09/41] x86/irq: Get rid of duplicated trace_x86_platform_ipi()  code Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
    Re: [patch 09/41] x86/irq: Get rid of duplicated  trace_x86_platform_ipi() code Steven Rostedt <rostedt@goodmis.org> - 2017-08-25 17:50 +0200
  [patch 12/41] x86/mce: Remove duplicated tracing interrupt code Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
    Re: [patch 12/41] x86/mce: Remove duplicated tracing interrupt code Steven Rostedt <rostedt@goodmis.org> - 2017-08-25 18:10 +0200
      Re: [patch 12/41] x86/mce: Remove duplicated tracing interrupt  code Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 18:20 +0200
  [patch 21/41] x86/gdt: Use bitfields for initialization Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
  [patch 28/41] x86/idt: Move early IDT setup out of 32bit asm Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
  [patch 22/41] x86/ldttss: Cleanup 32bit descriptors Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
  [patch 20/41] x86: Replace access to desc_struct:a/b fields Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
    Re: [patch 20/41] x86: Replace access to desc_struct:a/b fields Juergen Gross <jgross@suse.com> - 2017-08-25 13:20 +0200
    Re: [patch 20/41] x86: Replace access to desc_struct:a/b fields Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-08-25 16:00 +0200
      Re: [patch 20/41] x86: Replace access to desc_struct:a/b fields Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 16:10 +0200
        Re: [patch 20/41] x86: Replace access to desc_struct:a/b fields Steven Rostedt <rostedt@goodmis.org> - 2017-08-25 16:20 +0200
  [patch 04/41] x86/boot: Move EISA setup to a proper place Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
    Re: [patch 04/41] x86/boot: Move EISA setup to a proper place Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 14:00 +0200
  [patch 25/41] x86/idt: Remove unused set_trap_gate() Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
  [patch 08/41] x86/apic: Use this_cpu_ptr in local_timer_interrupt Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
  [patch 15/41] x86/idt: Remove tracing idt completely Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 13:10 +0200
    Re: [patch 15/41] x86/idt: Remove tracing idt completely Steven Rostedt <rostedt@goodmis.org> - 2017-08-25 23:20 +0200
      Re: [patch 15/41] x86/idt: Remove tracing idt completely Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 23:30 +0200
      Re: [patch 15/41] x86/idt: Remove tracing idt completely Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 23:30 +0200

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